The effects of artificial aging(T6)on the creep resistance with tensile stresses in the range of 50−80 MPa at 175℃were investigated for an extruded Mg−1.22Al−0.31Ca−0.44Mn(wt.%)alloy.The Guinier-Preston(G.P.)zones pr...The effects of artificial aging(T6)on the creep resistance with tensile stresses in the range of 50−80 MPa at 175℃were investigated for an extruded Mg−1.22Al−0.31Ca−0.44Mn(wt.%)alloy.The Guinier-Preston(G.P.)zones primarily precipitate in the sample aged at 200℃for 1 h(T6-200℃/1h),while the Al_(2)Ca phases mainly precipitate in the sample aged at 275℃for 8 h(T6-275℃/8h).The T6-200℃/1h sample exhibits excellent creep resistance,with a steady-state creep rate one order of magnitude lower than that of the T6-275℃/8h sample.The abnormally high stress exponent(~8.2)observed in the T6-200℃/1h sample is associated with the power-law breakdown mechanism.TEM analysis illuminates that the creep mechanism for the T6-200℃/1h sample is cross-slip between basal and prismatic dislocations,while the T6-275℃/8h sample exhibits a mixed mechanism of dislocation cross-slip and climb.Compared with the Al_(2)Ca phase,the dense G.P.zones effectively impede dislocation climb and glide during the creep process,demonstrating superior creep resistance of the T6-200℃/1h sample.展开更多
A series of high-strength wind power steels with various microstructural morphologies was produced by hot-rolled and thermo-mechanical controlled processes.The microstructure,microhardness,and tensile behavior observe...A series of high-strength wind power steels with various microstructural morphologies was produced by hot-rolled and thermo-mechanical controlled processes.The microstructure,microhardness,and tensile behavior observed using in-situ techniques in various types of steels were investigated.The experimental results demonstrated that the 3 microstructural morphologies(band-,net-,and fiber-structures)can be clarified and categorized;each type possesses different tensile strengths,yield behaviors,and strain hardening behaviors.This can be attributed to different strain distribution caused by the structural morphology;band-structure steels exhibit a yield plateau primarily attributed to the relatively weak constraint effect of pearlite on ferrite;net-structure steels display 3 strain hardening stages due to the staged plastic deformation;fiber-structure steels achieve superior strength through their uniform stress distribution.Furthermore,the initial strain hardening rate,transition strain,and uniform elongation were influenced by the features of the constituent phases.Based on these findings,methods for estimating the yield strength and tensile strength of the steels with two phases were discussed and experimentally validated.展开更多
Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed...Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.展开更多
We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic roc...We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic rock matrix are treated with distinct enrichment,and a recently proposed dualmechanism tensile failure criterion for transversely isotropic rocks is adopted to determine crack initiation for the two failure modes.The cohesive crack model is adopted to characterize the response of embedded cracks.As for the numerical implementation of the proposed framework,both algorithms for the update of local history variables at Gauss points and of the global finite element system are derived.Four boundary-value problem simulations are carried out with the proposed framework,including uniaxial tension tests of Argillite,pre-notched square loaded in tension,three-point bending tests on Longmaxi shale,and simulations of tensile cracks induced by a strip load around a tunnel in transversely isotropic rocks.Simulation results reveal that the proposed framework can properly capture the tensile strength anisotropy and the anisotropic evolution of tensile cracks in transversely isotropic rocks.展开更多
The tensile strength of rocks under real-time high-temperatures is essential for enhanced geothermal system development.However,the complex occurrence and deep burial of hot dry rocks limit the quantity and quality of...The tensile strength of rocks under real-time high-temperatures is essential for enhanced geothermal system development.However,the complex occurrence and deep burial of hot dry rocks limit the quantity and quality of standard samples for mechanical testing.This paper compared the tensile strengths obtained from Brazilian splitting tests on standard samples(with a diameter of 50 mm and a thickness of 25 mm)and micro-tensile samples(with a diameter of 50 mm and a thickness of 25 mm)of two types of granites.A power-law size effect model was established between the two sets of data,validating the reliability of the testing method.Then,miniature Brazilian splitting under real-time high-temperature,combined with X-ray diffraction(XRD)revealed temperature-dependent strength variations and microstructural damage mechanisms.The results show that:(1)The comparison error between the tensile strength obtained by the fitting model and that of the measured standard samples was less than 6%.(2)In real-time high-temperature conditions,tensile strength of granite exhibited non-monotonic behavior,increasing below 300°C before decreasing,with sharp declines at 400–500°C and 600–700°C.(3)Thermal damage stems from the differences in the high-temperature behavior of minerals,including dehydration,phase transformation,and differential expansion.展开更多
The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most stud...The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most studies focus on macroscopic fracture mechanical properties,and the mechanism linking the macroscopic fracture with the microcrack growth during the cyclic dynamic direct tensile loading of brittle rocks is rarely studied.In this paper,a micro-macro fracture model explaining the stress-strain constitutive relationship is established at the last impact failure after being subjected to multiple cyclic direct tensile impacts of brittle rocks.This model is based on the wing crack extension model under direct tensile loading,the quasi-static and dynamic fracture toughness relationship,the suggested crack rate and strain rate relationship,the relationship of damage and dynamic tensile fatigue life N,the relationship of dynamic fracture toughness and dynamic tensile fatigue life N.The variations of dynamic mechanical properties of rocks with dynamic tensile fatigue life for different initial crack sizes and angles within the rocks are further discussed.The compressive strength,elastic modulus,crack initiation stress,limit crack extension length and crack extension rate descend and the failure strain ascends with an increment of dynamic tensile fatigue life in rocks.This study's results provide help for the safety and stability of the underground surrounding rocks under blasting working or seismic disasters.展开更多
The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_...The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.展开更多
Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on t...Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.展开更多
This work aims to reveal the actual effect of Zn and Ca additions on tensile properties and bendability of a recently designed Mg-3Al-0.2Mn(mass%,AM30)sheet with high formability.We fabricated AM30 and Mg-3Al-0.8Zn-0....This work aims to reveal the actual effect of Zn and Ca additions on tensile properties and bendability of a recently designed Mg-3Al-0.2Mn(mass%,AM30)sheet with high formability.We fabricated AM30 and Mg-3Al-0.8Zn-0.5Ca-0.2Mn(mass%,AZXM3100)sheets with weakly aligned(0001)poles.Their deformation behaviors were thoroughly investigated using electron backscattered diffraction and crystal plasticity simulation.We found that the Zn and Ca additions were not effective in improving the ductility and formability.Both the sheets showed large elongation to failure of~30% in tension,and their maximum bending angles during three-point bending were~90°.In-depth characterization of the deformation behaviors revealed that the Zn and Ca additions slightly facilitated tensile twinning,and the activity of the non-basal prismatic slip did not increase in the AZXM3100.Moreover,the Al_(2)Ca phase,which was formed in the AZXM3100,promoted the formation and propagation of cracks by concentrating plastic deformation.Therefore,ductility and formability could not be improved even after the Zn and Ca additions.展开更多
The anisotropy and tension-compression asymmetry of rare-earth magnesium(Mg-RE) alloys have attracted significant attention.In this study,the room-temperature tensile anisotropy and tensioncompression asymmetry of the...The anisotropy and tension-compression asymmetry of rare-earth magnesium(Mg-RE) alloys have attracted significant attention.In this study,the room-temperature tensile anisotropy and tensioncompression asymmetry of the extruded Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy were investigated utilizing techniques such as optical microscopy(OM),electron backscatter diffraction(EBSD),and viscoplastic self-consistent(VPSC) modeling.Among the tensile samples,the TO sample(with axis parallel to extrusion direction) exhibits the greatest tensile yield strength(TYS) of 270 MPa and ultimate tensile strength(UTS) of 336 MPa,the T45 sample(with axis inclined at a 45° angle to extrusion direction) and T90 sample(with axis perpendicular to extrusion direction) exhibit lower TYS and UTS.The CO sample shows a slightly greater compressive yield strength(CYS) of 290 MPa.The ratio of TYS/CYS is approximately 1.07.This study significantly adjusts the VPSC hardening parameters through the Schmid factor of deformation mechanisms in Mg-RE alloy,particularly increasing the τ0(critical resolved shear stress,CRSS) and τ1values for basalslip and {10-12} twinning.The ratios of CRSS for other deformation mechanisms to basalslip are approximately as follows:CRSSTwin/CRSSBas=2,CRSSpri/CRSSBas≈2.7and CRSSPyr/CRSSBas≈3.3,while these ratios in traditional alloys are generally higher.The stress-strain curves and pole figures obtained from the modified VPSC model demonstrate excellent agreement with experimental results.According to the VPSC simulation results,the primary factor contributing to tensile anisotropy is the disparity in the activation levels of slip systems.The inclusion of rare-earth elements mitigates the tension-compression asymmetry by reducing the difference of CRSS between different deformation mechanisms.展开更多
Stress relaxation is a time-dependent phenomenon in rocks,characterized by a gradual decrease in stress magnitude while strain remains constant with time.This study introduces a novel experimental approach to investig...Stress relaxation is a time-dependent phenomenon in rocks,characterized by a gradual decrease in stress magnitude while strain remains constant with time.This study introduces a novel experimental approach to investigate deformation processes during the primary and secondary stages of stress relaxation and to differentiate the damage mechanisms occurring during relaxation from those under monotonic loading.To this end,the deformation behavior of prismatic-shaped homogeneous Stanstead granite(SG)rock specimens was monitored using two-dimensional digital image correlation(2D-DIC)in-sync with active ultrasonic sensing during stress relaxation and monotonic loading conditions.In particular,the SG specimens were allowed to undergo stress relaxation starting at a driving stress(σd)just above the crack damage(CD)threshold of the specimens,while their deformation characteristics were evaluated via 2D-DIC full-field strain maps and ultrasonic characteristics.The results indicate that the primary stage of relaxation is marked by accumulation of tensile damage at a decreasing rate,and the rate of damage accumulation reaches a steady state during the secondary stage of relaxation.Likewise,the ultrasonic amplitude reduced at a decreasing rate during the primary stage of relaxation and attained a constant rate of reduction during secondary relaxation.Additionally,a comparison of rock behavior during stress relaxation and monotonic loading conditions quantitatively demonstrated that SG dilates more during relaxation than under monotonic loading over a given range of damage values.This is interpreted to be associated with the fact that local extensional strains are diffuse under relaxation,in contrast with the more localized nature of damage under monotonic loading conditions.展开更多
This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded all...This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded alloys exhibit fully recrystallized microstructures with undissolved second-phase particles enriched with Ca and Y.The average grain size varies non-monotonically with Al content due to the competing effects of recrystallization kinetics,solute drag,and particle band distribution.As Al content increases,tensile strength increases,while ductility decreases.Notably,despite its relatively coarse grain structure,the SEN9 alloy exhibits significantly higher yield strength than the SEN6 alloy.This improvement is mainly attributed to additional precipitation strengthening from fine Mg_(17)Al_(12)discontinuous precipitates formed along grain boundaries.Meanwhile,the reduced elongation observed in the SEN9 and SEN11 alloys is attributed to premature fracture at coarse Mg_(17)(Al,Zn,Ca)_(12)particle bands aligned along the extrusion direction.From the SEN1 to SEN9 alloys,the fatigue strength(FS)increases approximately linearly with ultimate tensile strength(UTS),reaching 170 MPa.However,this FS-UTS proportionality fails in the SEN11 alloy,where FS falls to 120 MPa despite the highest UTS.This deviation from the FS-UTS correlation that is observed for the lower-Al-content alloys is attributed to the clustered distribution of coarse Mg_(17)(Al,Zn,Ca)_(12)particles in the SEN11 alloy,which promotes early crack initiation under cyclic loading.These findings emphasize the importance of controlled Al addition in enhancing both strength and fatigue resistance while also highlighting the adverse effects of excessive Al content owing to microstructural embrittlement.展开更多
This study investigated the validity and sensitivity of a custom-made shoelace tensile testing system.The aim was to analyze the distribution pattern of shoelace tension in different positions and under different tigh...This study investigated the validity and sensitivity of a custom-made shoelace tensile testing system.The aim was to analyze the distribution pattern of shoelace tension in different positions and under different tightness levels during running.Mechanical tests were conducted using 16 weights,and various statistical analyses,including linear regression,Bland-Altman plots,coefficient of variation,and intraclass correlation coefficient,were performed to assess the system’s validity.Fifteen male amateur runners participated in the study,and three conditions(loose,comfortable,and tight)were measured during an upright stance.The system utilized VICON motion systems,a Kistler force plate,and a Photoelectric gate speed measurement system.Results showed a linear relationship between voltage and load at the three sensors(R2≥0.9997).Bland-Altman plots demonstrated 95%prediction intervals within±1.96SD from zero for all sensors.The average coefficient of variation for each sensor was less than 0.38%.Intraclass correlation coefficient values were larger than 0.999(p<0.0001)for each sensor.The peak tension of the front shoelace was greater than that of the front and middle when the shoelace was loose and tight.The rear shoelace had the highest tension force.The study also found that shoelace tension varied throughout the gait cycle during running.Overall,this research provides a novel and validated method for measuring shoelace tensile stress,which has implications for developing automatic shoelace fastening systems.展开更多
The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The spec...The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The specimens were deformed under varying degrees of IPS strain(γ12=0.05,0.10,and 0.15)using a customized jig.Electron backscatter diffraction(EBSD)observations revealed profuse tensile twinning(TTW)even at an IPS strain of 0.05,with its intensity continuously increased as the IPS strain increased.The TTWs progressively engulfed parent grains with increasing shear strain,evolving into an unusual deformation twin morphology.Furthermore,VPSC model predictions confirmed basal slip as the dominant deformation mode at low IPS strains,transitioning to prismatic slip dominance at higher IPS strains.The activity of the TTW mode was significantly higher during the initial stages of IPS strain and saturated to lower values at higher strains.VPSC simulation results also indicated preferential shear accumulation on a single twin system,explaining the phenomenon of a single twin variant engulfing a parent grain.Additionally,the influence of individual slip and twin modes on texture evolution was evaluated through orientation tracking of representative grains at various shear strain increments using VPSC simulation.The simulation results quantitatively highlighted the activities of basal slip,prismatic slip,and tensile twinning,establishing a correlation between texture evolution and the underlying deformation mechanisms.展开更多
The microstructures,mechanical properties,and fracture behaviors of an Al-5.9Zn-1.9Mg alloy subjected to thermomechanical treatment across different pre-rolling temperatures have been exhaustively investigated in pres...The microstructures,mechanical properties,and fracture behaviors of an Al-5.9Zn-1.9Mg alloy subjected to thermomechanical treatment across different pre-rolling temperatures have been exhaustively investigated in present work.The pre-deformation temperature exerts a modest influence on grain morphology,while it profoundly impacts the dislocation configurations and precipitation behaviors.Elevating the rolling temperature from ambient to 170℃results in a reduction in dislocation density within grains accompanied by a notable enhancement in their distributional uniformity.While advancing the temperature to 320℃prompts the premature formation of precipitates during deformation,which diminishes the precipitation during the subsequent ageing.Tensile results reveal that the thermomechanical treatment incorporating pre-rolling at 170℃confers a substantial strengthening effect on the alloy on the basis of both grain boundary strengthening and dislocation strengthening stemmed from pre-deformation along with the precipitation strengthening generated by ageing.Furthermore,the microstructure exhibits a relatively scarce presence of inhomogeneous features such as dislocation pile-ups and micro shear bands,contributing favorably to enhance the ductility of the alloy that presents the mixture of cleavage fracture and dimple-induced failure.展开更多
In this work,mechanical properties,the tensile anisotropy,and deformation mechanisms during tensile testing of rolled Mg-6.3Gd-3Li-2Zn-0.5Al alloys(R2 and R4)were analyzed with Visco-Plastic Self-Consistent(VPSC)model...In this work,mechanical properties,the tensile anisotropy,and deformation mechanisms during tensile testing of rolled Mg-6.3Gd-3Li-2Zn-0.5Al alloys(R2 and R4)were analyzed with Visco-Plastic Self-Consistent(VPSC)model and material characterization techniques.The results showed that the mechanical properties of the rolled Mg-Gd-Li alloy displayed considerable anisotropy,with highest yield strength and tensile strength along the rolling direction(RD)measured at 272.3 MPa and 294.5 MPa,respectively.Conversely,the yield and tensile strength in the transverse direction(TD)were merely 214.7 MPa and 253.1 MPa,respectively.Furthermore,the anisotropy increased with the deformation.The VPSC models for rolled Mg-Gd-Li alloy in tensile deformation were constructed,respectively,by adjusting the hardening parameters.Pyramidal<c+a>slip,which dominated the deformation mechanisms of Mg-Gd-Li alloy,was calculated via VPSC model and observed in electron backscatter diffraction(EBSD)data.The stress-strain curves and pole figures generated from the VPSC model exhibited excellent agreement with experimental results.For the rolled Mg-Gd-Li alloy,the activation levels of basalslip along different tensile directions were the main cause of the anisotropy in yield strength.On the other hand,the activation levels of(10–12)twinning during deformation in various tensile orientations were primarily responsible for the anisotropy in tensile strength.展开更多
The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF a...The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF alloy with a small amount of nano-sizedωath particles inβmatrix possesses tensile strength of 697 MPa,elongation of~34%,Young’s modulus(YM)of 75 GPa,and impact toughness of 58.7 J/cm^(2).After aging at relatively lower temperatures of 400℃,the hardness and modulus of the alloy increased significantly,while the plasticity and toughness dropped sharply due to the precipitation ofωiso phase.ωiso phase displayed an ellipsoidal morphology with high volume fraction and a size of about 50 nm after aging at 400℃,leading to the highest hardness of 364 HV and YM of 108 GPa,along with completely embrittlement since elongation and toughness were almost zero.A brittle impact fracture morphology was observed in the alloy,which is dominated by intergranular fracture,with a mixed fracture characteristics of cleavage surfaces,terraces and tiny dimples.When aged at 550℃,plate-likeαdistributed inβmatrix uniformly and inβgrain boundaries in parallel,resulting in the high strength of 804 MPa,as well as lowest YM of 72 GPa,elongation of 9%and toughness of 35.8 J/cm^(2).The fracture morphology of the alloy aged at 550℃showed a ductile fracture mechanism with a large number of dimples.展开更多
Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims ...Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims to investigate the influence of plant roots on the tensile strength of soil.For this investigation,Amorpha fruticose was selected due to its large root diameter and the ease of root extraction.Indoor tensile tests were conducted on individual roots and root-soil complexes under three varying factors.The results indicate a power law relationship between root diameter and tensile strength.Increased root content and dry density notably enhance the tensile strength of the root-soil complex while roots mitigate damage associated with soil brittleness.When root content increases from 0 to 10,the maximum enhancement in tensile strength of the root-soil complex reaches 42.3 kPa.The tensile strength of the root-soil complex at a dry density of 1.7 g/cm^(3)is four to five times greater than that of the complex at a dry density of 1.4 g/cm^(3).Moreover,as moisture content increases,the tensile strength of the root-soil complex initially rises before declining,with an increase range of 7.7-35.8 kPa.These findings provide a scientific basis for understanding the role of vegetation roots in soil tensile strength and for guiding slope reinforcement strategies.展开更多
Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electric...Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.展开更多
The effects of tungsten inert gas arc-assisted friction stir welding(TIG-FSW)on the microstructure,tensile properties and corrosion resistance of AA6016 and AA2519 alloys lap joints were investigated by means of optic...The effects of tungsten inert gas arc-assisted friction stir welding(TIG-FSW)on the microstructure,tensile properties and corrosion resistance of AA6016 and AA2519 alloys lap joints were investigated by means of optical microscope,scanning electron microscope,tensile test at room temperature,corrosion immersion tests and electrochemical measurements.The results show that the introduction of TIG arc during FSW process results in a more uniform microstructure of the joint with no tunnel hole defects.Furthermore,it enhances tensile strength and elongation of the joint with increased rates of 11.5%and 50.0%,respectively;meanwhile,the corrosion current density and largest corrosion depth are decreased with reduction rates of 78.2%and 45.7%,respectively.TIG-FSW can promote flow,contact and diffusion of materials,thus improving microstructure of the joint.Additionally,it reduces the size and number of secondary phase particles.Consequently,these factors contribute to the higher tensile properties and corrosion resistance of the joints.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 52175322, 52271031)the Natural Science Foundation of Jilin Province, China (No. SKL202302015)。
文摘The effects of artificial aging(T6)on the creep resistance with tensile stresses in the range of 50−80 MPa at 175℃were investigated for an extruded Mg−1.22Al−0.31Ca−0.44Mn(wt.%)alloy.The Guinier-Preston(G.P.)zones primarily precipitate in the sample aged at 200℃for 1 h(T6-200℃/1h),while the Al_(2)Ca phases mainly precipitate in the sample aged at 275℃for 8 h(T6-275℃/8h).The T6-200℃/1h sample exhibits excellent creep resistance,with a steady-state creep rate one order of magnitude lower than that of the T6-275℃/8h sample.The abnormally high stress exponent(~8.2)observed in the T6-200℃/1h sample is associated with the power-law breakdown mechanism.TEM analysis illuminates that the creep mechanism for the T6-200℃/1h sample is cross-slip between basal and prismatic dislocations,while the T6-275℃/8h sample exhibits a mixed mechanism of dislocation cross-slip and climb.Compared with the Al_(2)Ca phase,the dense G.P.zones effectively impede dislocation climb and glide during the creep process,demonstrating superior creep resistance of the T6-200℃/1h sample.
基金funded by the National Key Research and Development Program of China(No.2022YFB3708200)。
文摘A series of high-strength wind power steels with various microstructural morphologies was produced by hot-rolled and thermo-mechanical controlled processes.The microstructure,microhardness,and tensile behavior observed using in-situ techniques in various types of steels were investigated.The experimental results demonstrated that the 3 microstructural morphologies(band-,net-,and fiber-structures)can be clarified and categorized;each type possesses different tensile strengths,yield behaviors,and strain hardening behaviors.This can be attributed to different strain distribution caused by the structural morphology;band-structure steels exhibit a yield plateau primarily attributed to the relatively weak constraint effect of pearlite on ferrite;net-structure steels display 3 strain hardening stages due to the staged plastic deformation;fiber-structure steels achieve superior strength through their uniform stress distribution.Furthermore,the initial strain hardening rate,transition strain,and uniform elongation were influenced by the features of the constituent phases.Based on these findings,methods for estimating the yield strength and tensile strength of the steels with two phases were discussed and experimentally validated.
基金supported by the Pazy Foundation of the Israel Atomic Energy Commission and the Israeli Council of Higher Education(Grant No.322/20)。
文摘Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.
基金supported by the National Natural Science Foundation of China(Grant Nos.52038005 and 52201326)the fellowship of China Postdoctoral Science Foundation(Grant No.2022M721883)Tsinghua University Initiative Scientific Research Program.
文摘We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks.Fractures along the weak bedding planes and through the anisotropic rock matrix are treated with distinct enrichment,and a recently proposed dualmechanism tensile failure criterion for transversely isotropic rocks is adopted to determine crack initiation for the two failure modes.The cohesive crack model is adopted to characterize the response of embedded cracks.As for the numerical implementation of the proposed framework,both algorithms for the update of local history variables at Gauss points and of the global finite element system are derived.Four boundary-value problem simulations are carried out with the proposed framework,including uniaxial tension tests of Argillite,pre-notched square loaded in tension,three-point bending tests on Longmaxi shale,and simulations of tensile cracks induced by a strip load around a tunnel in transversely isotropic rocks.Simulation results reveal that the proposed framework can properly capture the tensile strength anisotropy and the anisotropic evolution of tensile cracks in transversely isotropic rocks.
基金supported by the National Natural Science Foundation of China(Nos.52174175 and 52274078)the Program for the Scientific and Technological Innovation Team in Universities of Henan Province(No.23IRTSTHN005)。
文摘The tensile strength of rocks under real-time high-temperatures is essential for enhanced geothermal system development.However,the complex occurrence and deep burial of hot dry rocks limit the quantity and quality of standard samples for mechanical testing.This paper compared the tensile strengths obtained from Brazilian splitting tests on standard samples(with a diameter of 50 mm and a thickness of 25 mm)and micro-tensile samples(with a diameter of 50 mm and a thickness of 25 mm)of two types of granites.A power-law size effect model was established between the two sets of data,validating the reliability of the testing method.Then,miniature Brazilian splitting under real-time high-temperature,combined with X-ray diffraction(XRD)revealed temperature-dependent strength variations and microstructural damage mechanisms.The results show that:(1)The comparison error between the tensile strength obtained by the fitting model and that of the measured standard samples was less than 6%.(2)In real-time high-temperature conditions,tensile strength of granite exhibited non-monotonic behavior,increasing below 300°C before decreasing,with sharp declines at 400–500°C and 600–700°C.(3)Thermal damage stems from the differences in the high-temperature behavior of minerals,including dehydration,phase transformation,and differential expansion.
基金supported by the National Natural Science Foundation of China(Grant Nos.51708016,52438007 and 12172036)the R&D program of Beijing Municipal Education Commission(Grant No.KM202110016014)+1 种基金the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20200307)the Graduate Innovation Program of Beijing University of Civil Engineering and Architecture(Grant No.PG2025060).
文摘The fatigue fracture under cyclic dynamic direct tensions of brittle rock is an important mechanical characteristic index for the evaluation of geological disasters and underground engineering safety.However,most studies focus on macroscopic fracture mechanical properties,and the mechanism linking the macroscopic fracture with the microcrack growth during the cyclic dynamic direct tensile loading of brittle rocks is rarely studied.In this paper,a micro-macro fracture model explaining the stress-strain constitutive relationship is established at the last impact failure after being subjected to multiple cyclic direct tensile impacts of brittle rocks.This model is based on the wing crack extension model under direct tensile loading,the quasi-static and dynamic fracture toughness relationship,the suggested crack rate and strain rate relationship,the relationship of damage and dynamic tensile fatigue life N,the relationship of dynamic fracture toughness and dynamic tensile fatigue life N.The variations of dynamic mechanical properties of rocks with dynamic tensile fatigue life for different initial crack sizes and angles within the rocks are further discussed.The compressive strength,elastic modulus,crack initiation stress,limit crack extension length and crack extension rate descend and the failure strain ascends with an increment of dynamic tensile fatigue life in rocks.This study's results provide help for the safety and stability of the underground surrounding rocks under blasting working or seismic disasters.
文摘The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.
基金supported by the National Natural Science Foundation of China(No.51974212)the China Baowu Low Carbon Metallurgy Innovation Foundation(No.BWLCF202116)+2 种基金the Science and Technology Major Project of Wuhan(No.2023020302020572)the Postdoctor Project of Hubei Province(No.2024HBBHCXA074)the Foundation of Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education(No.FMRUlab23-04).
文摘Coke is the only solid charge component in the lower part of the blast furnace,and its strength is crucial to its production.Si and Al are the two most abundant elements in coke ash.The influences of these oxides on the tensile strength of the coke matrix were studied by splitting tests.According to the Weibull analysis,with increasing Si and Al oxide concentrations,the fracture stress range of the coke widened,the upper and lower limits decreased,the probability of fracture under the same stress conditions increased,and the randomness and dispersion of strength increased.These results can be attributed to the inhibitory effect of ash during coal pyrolysis.Ash impedes the growth and contact of mesophase,leading to a decrease in graphitic carbon structures and an increase in edge carbon and aliphatic carbon structures in the resulting coke.Consequently,the overall ordering of the carbon structure is reduced.Moreover,SiO_(2)and Al_(2)O_(3)promoted the development of coke pores,thinned the coke pore wall,and significantly increased the proportion of large pores(>500μm).Moreover,Al_(2)O_(3)had more significant influences on the coke strength,carbon structure and stomatal ratio than SiO_(2).In addition,the position where the ash particles bonded to the carbon matrix easily produced cracks and holes,and the sharp edge of the matrix was likely to produce stress concentration points when subjected to an external force,leading to structural damage.Therefore,controlling the concentration of ash could effectively reduce the number of structural defects inside coke,which is conducive to improving the strength.
基金supported by JSPS KAKENHI Grant Numbers JP22H00259,JP21H01669Osawa Scientific Studies Grants Foundation,Japan+3 种基金The Light Metal Educational Foundation,Inc.Japan,Natural Science Foundation of Heilongjiang Province-Outstanding Youth Fund(Grant No YQ2020E006)National Natural Science Foundation of China(52220105003,51971075)National Key Research&Development Program of China(2021YFB3703300,2022YFE0110600).
文摘This work aims to reveal the actual effect of Zn and Ca additions on tensile properties and bendability of a recently designed Mg-3Al-0.2Mn(mass%,AM30)sheet with high formability.We fabricated AM30 and Mg-3Al-0.8Zn-0.5Ca-0.2Mn(mass%,AZXM3100)sheets with weakly aligned(0001)poles.Their deformation behaviors were thoroughly investigated using electron backscattered diffraction and crystal plasticity simulation.We found that the Zn and Ca additions were not effective in improving the ductility and formability.Both the sheets showed large elongation to failure of~30% in tension,and their maximum bending angles during three-point bending were~90°.In-depth characterization of the deformation behaviors revealed that the Zn and Ca additions slightly facilitated tensile twinning,and the activity of the non-basal prismatic slip did not increase in the AZXM3100.Moreover,the Al_(2)Ca phase,which was formed in the AZXM3100,promoted the formation and propagation of cracks by concentrating plastic deformation.Therefore,ductility and formability could not be improved even after the Zn and Ca additions.
基金Project supported by the Key Research and Development Program of Heilongjiang (2022ZX01A01)National Natural Science Foundation of China (51975167)Natural Science Foundation of Heilongjiang Province(LH2022E080)
文摘The anisotropy and tension-compression asymmetry of rare-earth magnesium(Mg-RE) alloys have attracted significant attention.In this study,the room-temperature tensile anisotropy and tensioncompression asymmetry of the extruded Mg-8.5Gd-4.5Y-0.8Zn-0.4Zr alloy were investigated utilizing techniques such as optical microscopy(OM),electron backscatter diffraction(EBSD),and viscoplastic self-consistent(VPSC) modeling.Among the tensile samples,the TO sample(with axis parallel to extrusion direction) exhibits the greatest tensile yield strength(TYS) of 270 MPa and ultimate tensile strength(UTS) of 336 MPa,the T45 sample(with axis inclined at a 45° angle to extrusion direction) and T90 sample(with axis perpendicular to extrusion direction) exhibit lower TYS and UTS.The CO sample shows a slightly greater compressive yield strength(CYS) of 290 MPa.The ratio of TYS/CYS is approximately 1.07.This study significantly adjusts the VPSC hardening parameters through the Schmid factor of deformation mechanisms in Mg-RE alloy,particularly increasing the τ0(critical resolved shear stress,CRSS) and τ1values for basalslip and {10-12} twinning.The ratios of CRSS for other deformation mechanisms to basalslip are approximately as follows:CRSSTwin/CRSSBas=2,CRSSpri/CRSSBas≈2.7and CRSSPyr/CRSSBas≈3.3,while these ratios in traditional alloys are generally higher.The stress-strain curves and pole figures obtained from the modified VPSC model demonstrate excellent agreement with experimental results.According to the VPSC simulation results,the primary factor contributing to tensile anisotropy is the disparity in the activation levels of slip systems.The inclusion of rare-earth elements mitigates the tension-compression asymmetry by reducing the difference of CRSS between different deformation mechanisms.
基金support provided by the Indian Institute of Technology Delhi,India,and Colorado School of Mines,USA,for performing the work related to this research article is greatly appreciatedsupported by the IIT Delhi MFIRP Grant No.MI022762G+1 种基金partially by the U.S.Department of Energy,Office of Basic Energy Sciences,under Award Number DE-SC0019117support is gratefully acknowledged。
文摘Stress relaxation is a time-dependent phenomenon in rocks,characterized by a gradual decrease in stress magnitude while strain remains constant with time.This study introduces a novel experimental approach to investigate deformation processes during the primary and secondary stages of stress relaxation and to differentiate the damage mechanisms occurring during relaxation from those under monotonic loading.To this end,the deformation behavior of prismatic-shaped homogeneous Stanstead granite(SG)rock specimens was monitored using two-dimensional digital image correlation(2D-DIC)in-sync with active ultrasonic sensing during stress relaxation and monotonic loading conditions.In particular,the SG specimens were allowed to undergo stress relaxation starting at a driving stress(σd)just above the crack damage(CD)threshold of the specimens,while their deformation characteristics were evaluated via 2D-DIC full-field strain maps and ultrasonic characteristics.The results indicate that the primary stage of relaxation is marked by accumulation of tensile damage at a decreasing rate,and the rate of damage accumulation reaches a steady state during the secondary stage of relaxation.Likewise,the ultrasonic amplitude reduced at a decreasing rate during the primary stage of relaxation and attained a constant rate of reduction during secondary relaxation.Additionally,a comparison of rock behavior during stress relaxation and monotonic loading conditions quantitatively demonstrated that SG dilates more during relaxation than under monotonic loading over a given range of damage values.This is interpreted to be associated with the fact that local extensional strains are diffuse under relaxation,in contrast with the more localized nature of damage under monotonic loading conditions.
基金supported by the Materials and Components Technology Development Program(No.20024843)funded by the Ministry of Trade,Industry&Energy(MOTIE,South Korea)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00450561).
文摘This study systematically investigates the effects of Al content on the microstructure,tensile properties,and high-cycle fatigue behavior of extruded Mg-xAl-Zn-Ca-Y(SENx)alloys.The results reveal that all extruded alloys exhibit fully recrystallized microstructures with undissolved second-phase particles enriched with Ca and Y.The average grain size varies non-monotonically with Al content due to the competing effects of recrystallization kinetics,solute drag,and particle band distribution.As Al content increases,tensile strength increases,while ductility decreases.Notably,despite its relatively coarse grain structure,the SEN9 alloy exhibits significantly higher yield strength than the SEN6 alloy.This improvement is mainly attributed to additional precipitation strengthening from fine Mg_(17)Al_(12)discontinuous precipitates formed along grain boundaries.Meanwhile,the reduced elongation observed in the SEN9 and SEN11 alloys is attributed to premature fracture at coarse Mg_(17)(Al,Zn,Ca)_(12)particle bands aligned along the extrusion direction.From the SEN1 to SEN9 alloys,the fatigue strength(FS)increases approximately linearly with ultimate tensile strength(UTS),reaching 170 MPa.However,this FS-UTS proportionality fails in the SEN11 alloy,where FS falls to 120 MPa despite the highest UTS.This deviation from the FS-UTS correlation that is observed for the lower-Al-content alloys is attributed to the clustered distribution of coarse Mg_(17)(Al,Zn,Ca)_(12)particles in the SEN11 alloy,which promotes early crack initiation under cyclic loading.These findings emphasize the importance of controlled Al addition in enhancing both strength and fatigue resistance while also highlighting the adverse effects of excessive Al content owing to microstructural embrittlement.
文摘This study investigated the validity and sensitivity of a custom-made shoelace tensile testing system.The aim was to analyze the distribution pattern of shoelace tension in different positions and under different tightness levels during running.Mechanical tests were conducted using 16 weights,and various statistical analyses,including linear regression,Bland-Altman plots,coefficient of variation,and intraclass correlation coefficient,were performed to assess the system’s validity.Fifteen male amateur runners participated in the study,and three conditions(loose,comfortable,and tight)were measured during an upright stance.The system utilized VICON motion systems,a Kistler force plate,and a Photoelectric gate speed measurement system.Results showed a linear relationship between voltage and load at the three sensors(R2≥0.9997).Bland-Altman plots demonstrated 95%prediction intervals within±1.96SD from zero for all sensors.The average coefficient of variation for each sensor was less than 0.38%.Intraclass correlation coefficient values were larger than 0.999(p<0.0001)for each sensor.The peak tension of the front shoelace was greater than that of the front and middle when the shoelace was loose and tight.The rear shoelace had the highest tension force.The study also found that shoelace tension varied throughout the gait cycle during running.Overall,this research provides a novel and validated method for measuring shoelace tensile stress,which has implications for developing automatic shoelace fastening systems.
文摘The evolution of microstructure and texture in Mg-3Al-1Zn-1Ca alloy sheets subjected to in-plane shear(IPS)loading was investigated using experimental techniques and viscoplastic self-consistent(VPSC)modeling.The specimens were deformed under varying degrees of IPS strain(γ12=0.05,0.10,and 0.15)using a customized jig.Electron backscatter diffraction(EBSD)observations revealed profuse tensile twinning(TTW)even at an IPS strain of 0.05,with its intensity continuously increased as the IPS strain increased.The TTWs progressively engulfed parent grains with increasing shear strain,evolving into an unusual deformation twin morphology.Furthermore,VPSC model predictions confirmed basal slip as the dominant deformation mode at low IPS strains,transitioning to prismatic slip dominance at higher IPS strains.The activity of the TTW mode was significantly higher during the initial stages of IPS strain and saturated to lower values at higher strains.VPSC simulation results also indicated preferential shear accumulation on a single twin system,explaining the phenomenon of a single twin variant engulfing a parent grain.Additionally,the influence of individual slip and twin modes on texture evolution was evaluated through orientation tracking of representative grains at various shear strain increments using VPSC simulation.The simulation results quantitatively highlighted the activities of basal slip,prismatic slip,and tensile twinning,establishing a correlation between texture evolution and the underlying deformation mechanisms.
基金Project(ZZYJKT2025-03) supported by the Project of State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,ChinaProject(2024YFB3411200) supported by the National Key Research and Development Program of China。
文摘The microstructures,mechanical properties,and fracture behaviors of an Al-5.9Zn-1.9Mg alloy subjected to thermomechanical treatment across different pre-rolling temperatures have been exhaustively investigated in present work.The pre-deformation temperature exerts a modest influence on grain morphology,while it profoundly impacts the dislocation configurations and precipitation behaviors.Elevating the rolling temperature from ambient to 170℃results in a reduction in dislocation density within grains accompanied by a notable enhancement in their distributional uniformity.While advancing the temperature to 320℃prompts the premature formation of precipitates during deformation,which diminishes the precipitation during the subsequent ageing.Tensile results reveal that the thermomechanical treatment incorporating pre-rolling at 170℃confers a substantial strengthening effect on the alloy on the basis of both grain boundary strengthening and dislocation strengthening stemmed from pre-deformation along with the precipitation strengthening generated by ageing.Furthermore,the microstructure exhibits a relatively scarce presence of inhomogeneous features such as dislocation pile-ups and micro shear bands,contributing favorably to enhance the ductility of the alloy that presents the mixture of cleavage fracture and dimple-induced failure.
基金the financial support provided by Key Research and Development Program of Heilongjiang(Grant No.2022ZX01A01)Natural Science Found of Heilongjiang Province(LH2022E080).
文摘In this work,mechanical properties,the tensile anisotropy,and deformation mechanisms during tensile testing of rolled Mg-6.3Gd-3Li-2Zn-0.5Al alloys(R2 and R4)were analyzed with Visco-Plastic Self-Consistent(VPSC)model and material characterization techniques.The results showed that the mechanical properties of the rolled Mg-Gd-Li alloy displayed considerable anisotropy,with highest yield strength and tensile strength along the rolling direction(RD)measured at 272.3 MPa and 294.5 MPa,respectively.Conversely,the yield and tensile strength in the transverse direction(TD)were merely 214.7 MPa and 253.1 MPa,respectively.Furthermore,the anisotropy increased with the deformation.The VPSC models for rolled Mg-Gd-Li alloy in tensile deformation were constructed,respectively,by adjusting the hardening parameters.Pyramidal<c+a>slip,which dominated the deformation mechanisms of Mg-Gd-Li alloy,was calculated via VPSC model and observed in electron backscatter diffraction(EBSD)data.The stress-strain curves and pole figures generated from the VPSC model exhibited excellent agreement with experimental results.For the rolled Mg-Gd-Li alloy,the activation levels of basalslip along different tensile directions were the main cause of the anisotropy in yield strength.On the other hand,the activation levels of(10–12)twinning during deformation in various tensile orientations were primarily responsible for the anisotropy in tensile strength.
基金supported by the Natural Science Foundation of Hunan Province(2023JJ50055,2023JJ30081)the Science Research Foundation of Hunan Provincial Education Department(21A0546)+1 种基金the Youth Project of the National Natural Science Foundation of China(62003056)the Open Fund of Hunan Engineering Research Center of Research and Development of Degradable Materials and Molding Technology(2023KFKT05).
文摘The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF alloy with a small amount of nano-sizedωath particles inβmatrix possesses tensile strength of 697 MPa,elongation of~34%,Young’s modulus(YM)of 75 GPa,and impact toughness of 58.7 J/cm^(2).After aging at relatively lower temperatures of 400℃,the hardness and modulus of the alloy increased significantly,while the plasticity and toughness dropped sharply due to the precipitation ofωiso phase.ωiso phase displayed an ellipsoidal morphology with high volume fraction and a size of about 50 nm after aging at 400℃,leading to the highest hardness of 364 HV and YM of 108 GPa,along with completely embrittlement since elongation and toughness were almost zero.A brittle impact fracture morphology was observed in the alloy,which is dominated by intergranular fracture,with a mixed fracture characteristics of cleavage surfaces,terraces and tiny dimples.When aged at 550℃,plate-likeαdistributed inβmatrix uniformly and inβgrain boundaries in parallel,resulting in the high strength of 804 MPa,as well as lowest YM of 72 GPa,elongation of 9%and toughness of 35.8 J/cm^(2).The fracture morphology of the alloy aged at 550℃showed a ductile fracture mechanism with a large number of dimples.
基金The authors would like to acknowledge financial support from the Joint Funds of the National Nature Science Foundation of China(No.U22A20232)Supported by Open Project Funding of Key Laboratory of Intelligent Health Perception and Ecological Restoration of Rivers and Lakes,Ministry of Education(HGKFZ07)+2 种基金the National Natural Science Foundation of China(No.51978249)Innovation Research Team Project of the Hubei Provincial Department of Science and Technology(JCZRQT202500027)the International Collaborative Research Fund for Young Scholars in the Innovation Demonstration Base of Ecological Environment Geotechnical and Ecological Restoration of Rivers and Lakes.
文摘Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims to investigate the influence of plant roots on the tensile strength of soil.For this investigation,Amorpha fruticose was selected due to its large root diameter and the ease of root extraction.Indoor tensile tests were conducted on individual roots and root-soil complexes under three varying factors.The results indicate a power law relationship between root diameter and tensile strength.Increased root content and dry density notably enhance the tensile strength of the root-soil complex while roots mitigate damage associated with soil brittleness.When root content increases from 0 to 10,the maximum enhancement in tensile strength of the root-soil complex reaches 42.3 kPa.The tensile strength of the root-soil complex at a dry density of 1.7 g/cm^(3)is four to five times greater than that of the complex at a dry density of 1.4 g/cm^(3).Moreover,as moisture content increases,the tensile strength of the root-soil complex initially rises before declining,with an increase range of 7.7-35.8 kPa.These findings provide a scientific basis for understanding the role of vegetation roots in soil tensile strength and for guiding slope reinforcement strategies.
基金supported by the National Natural Science Foundation of China(No.51704087)the Natural Science Foundation of Heilongjiang Province(No.LH2020E083).
文摘Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.
文摘The effects of tungsten inert gas arc-assisted friction stir welding(TIG-FSW)on the microstructure,tensile properties and corrosion resistance of AA6016 and AA2519 alloys lap joints were investigated by means of optical microscope,scanning electron microscope,tensile test at room temperature,corrosion immersion tests and electrochemical measurements.The results show that the introduction of TIG arc during FSW process results in a more uniform microstructure of the joint with no tunnel hole defects.Furthermore,it enhances tensile strength and elongation of the joint with increased rates of 11.5%and 50.0%,respectively;meanwhile,the corrosion current density and largest corrosion depth are decreased with reduction rates of 78.2%and 45.7%,respectively.TIG-FSW can promote flow,contact and diffusion of materials,thus improving microstructure of the joint.Additionally,it reduces the size and number of secondary phase particles.Consequently,these factors contribute to the higher tensile properties and corrosion resistance of the joints.
