The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at c...The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at current density of 60 A/mm^(2) and strain rate of 0.1 s^(−1),the ultimate tensile stress shows a significant decrease from approximately 3000 MPa to 1900 MPa with reduction ratio of about 36.7%.However,as current density increases,elongation decreases due to intermediate temperature embrittlement.This is because the current induces Joule effect,which then leads to stress concentration and more defect formation.Moreover,the flow stress is decreased with the increase in strain rate at constant current density.展开更多
In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain r...In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).展开更多
This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-sha...This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities,combined with digital speckle and acoustic emission(AE)monitoring.The results show that as the dip angle of the primary joint increases,the failure mode transitions from overall failure to wedge block ejection and shear failure.A failure mode identification model was established based on main crack dip angle thresholds(40°,45°),uniaxial compressive strength thresholds(40,90 MPa),and energy core zone proportion thresholds(20%,10%),achieving an accuracy of 93.3%.In the overall failure and wedge block ejection modes,a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase(>0.6σ_(c)),while in the shear failure mode,significant fluctuations are observed due to the shear-tension alternation,making it difficult to identify a single critical point.Additionally,joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase(>0.8σ_(c)).These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.展开更多
The regulation of martensitic transformation and intrinsic brittleness are critical issues for the application of Ni-Mn-Ga shape memory alloys,and they are closely related to the alloy composition andγphase.In this s...The regulation of martensitic transformation and intrinsic brittleness are critical issues for the application of Ni-Mn-Ga shape memory alloys,and they are closely related to the alloy composition andγphase.In this study,single and dual-phase Ni_(55+x)Mn_(25)Ga_(20-x)(x=0,2,4 and 6)alloys were fabricated.The proportion of theγphase was elevated gradually,and the peak martensitic transformation temperature was enhanced from 350 to 460℃ with an increasing Ni/Ga ratio.The microstructures of theγphase were further regulated from continuous block to dispersed granular after annealing.The annealed dual-phase alloy with x=2 exhibited greater yield stress,compressive strength and toughness than the annealed single-phase alloy.It maintained plastic deformation without fracture,even at a strain of 30%.High strain energy and dislocation density were observed in the martensite of the dual-phase alloy,which can be attributed toγphases and the interface between martensite andγphases.Furthermore,[001]-oriented martensite variants were obtained during deformation in the dual-phase alloy.They were parallel to the loading direction and conducive to improving the compressive strength.This protocol provides in-depth insight into the influence of theγphase on the texture evolution and mechanical behavior of martensite during deformation.展开更多
High-purity silver(Ag)is extensively utilized in electronics,aerospace,and other advanced industries due to its excellent thermal conductivity,electrical conductivity,and machinability.However,the prohibitive material...High-purity silver(Ag)is extensively utilized in electronics,aerospace,and other advanced industries due to its excellent thermal conductivity,electrical conductivity,and machinability.However,the prohibitive material cost poses substantial challenges for optimizing thermal processing parameters through repetitive experimental trials.In this work,hot compression experiments on high-purity silver were conducted using a Gleeble-3800 thermal simulator.The high temperature deformation behaviors,dynamic recovery(DRV)and dynamic recrystallization(DRX)of high-purity silver were studied by constructing an Arrhenius constitutive equation and developing thermal processing maps.The results show that plastic instability of high-purity silver occurs at high strain rates and the optimized hot processing parameters are the strain rate below 0.001 s^(−1) and the temperature of 340−400℃.Microstructural observations exhibit that DRV prefers to occur at lower deformation temperatures(e.g.,250℃).This is attributed to the low stacking fault energy of high-purity silver,which facilitates the decomposition of dislocations into partial dislocations and promotes high-density dislocation accumulation.Furthermore,DRX in high-purity silver becomes increasingly pronounced with increasing deformation temperature and reaches saturation at 350℃.展开更多
The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling be...The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling before the recovery of a secondary stope,resulting in a layered structure of backfill in stope.Therefore,it is significant to investigate the deformation responses and mechanical properties of stratified cemented tailings backfill(SCTB)with different layer structures to remain self-standing as an artificial pillar in the primary stope.The current work examined the effects of enhance layer position(1/3,1/2,and 2/3)and thickness ratio(0,0.1,0.2,and 0.3)on the mechanical properties,deformation,energy evolution,microstructures,and failure modes of SCTB.The results demonstrate that the incorporation of an enhance layer significantly strengthens the deformation and strength of SCTB.Under a confining pressure of 50 kPa,the peak deviatoric stress rises from 525.6 to 560.3,597.1,and 790.5 kPa as the thickness ratio of enhance layer is increased from 0 to 0.1,0.2,and 0.3,representing a significant increase of 6.6%,13.6%,and 50.4%.As the confining pressure increases,the slopes of the curves in the elastic stage become steep,and the plastic phase is extended accordingly.Additionally,the incorporation of the enhance layer significantly improves the energy storage linit of SCTB specimen.As the thickness ratio of the enhance layer increases from 0 to 0.1,0.2,and 0.3,the elastic energy rises from 0.54 to 0.67,0.84,and 1.00 MJ·m^(-3),representing a significant increase of 24.1%,55.6%,and 85.2%.The internal friction angles and cohesions of the SCTB specimens are higher than those of the CTB specimens,however,the cohesion is more susceptible to enhance layer position and thickness ratio than the internal friction angle.The failure style of the SCTB specimen changes from shear failure to splitting bulging failure and shear bulging failure with the presence of an enhance layer.The crack propagation path is significantly blocked by the enhance layer.The findings are of great significance to the application and stability of the SCTB in subsequent stoping backfilling mines.展开更多
The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot...The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot provide information on the structure evolution during deformation.In order to investigate the failure mechanism of Al alloy foam under quasi-static compression,by utilizing X-ray imaging technology,in situ CT image data were obtained during the loading process.A geometric model characterizing the real structure of Al alloy foam was reconstructed from the initial CT images and used for finite element simulation.Besides,based on the digital volume correlation(DVC)method,the displacement and strain fields of Al alloy foam were calculated.The results show that the in situ experimental observation based on X-ray imaging can effectively obtain the failure information of Al alloy foam.The simulation results for deformation and failure behavior of Al alloy foam are consistent with experimental results.During the quasi-static compression,a shear band can be observed diagonally across the profile of Al alloy foam,with weak regions occurring in the cells with larger volume and higher aspect ratios.Using these weak regions as boundaries,the relative displacement of cell structures on one side compared to another side was identified as the intrinsic cause of shear band formation.The high-strain regions identified by DVC closely match the crack locations on the cell walls,validating the accuracy of DVC on localizing cracks on cell walls and predicting their propagation trends.展开更多
Multi-pass hot processing methods are commonly used in magnesium(Mg)alloys to overcome the poor workability due to limited slip systems,which generally involve complicated post-deformation softening and hardening beha...Multi-pass hot processing methods are commonly used in magnesium(Mg)alloys to overcome the poor workability due to limited slip systems,which generally involve complicated post-deformation softening and hardening behaviors.In this work,to reveal post-deformation softening and hardening mechanisms of a Mg-2Y-1Zn alloy,double-stage hot compression tests and microstructural observations were conducted.The results showed that the softening fraction of Mg-2Y-1Zn alloy showed a non-linear dependence on deformation conditions and could be general coupled by Z parameter.Due to the formation and cross-overlapping of twins and kinks,only static recovery(SRV)occurred during holding process at 300℃/0.001 s^(-1) which led to the least static softening:5.52% after 10 s of holding.For samples at 400℃/0.001s^(-1),the enhanced post-deformation softening,which is 11.93% after 10 s of holding,was attributed to static recrystallization(SRX)followed continuous dynamic recrystallization(CDRX)happened during first deformation stage as well as SRV influenced by the LPSO phases.Under deformation condition of 400℃/0.1 s^(-1),the coupled meta-dynamic recrystallization(MDRX)and SRX resulted in serious stress relaxation,which is 42.83% after 10 s of holding,and caused hardening phenomenon at reloading stage.The 18R-LPSO and 14H-LPSO phases synchronously worked on deformation behaviors and limited the growth of recrystallized grains.Further,a simplified static softening kinetics model was established based on Johnson-Mehl-Avrami-Kolmogorov equation and employed to rationalize experimental data.展开更多
Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under...Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under uniaxial tension along rolling direction(RD)and transverse direction(TD)at-50,25,50,and 150℃.Results reveal a transition from high strength with limited elongation at-50℃ to significant softening and maximum ductility at 150℃.TD samples consistently showed 2%-6%higher strength than RD;however,this yield anisotropy diminished at 150℃ due to the shift from twinning to thermally activated slip and recovery.Fractography indicated a change from semi-brittle to fully ductile fracture with increasing temperature.Electron backscattered diffraction(EBSD)analysis confirmed twinning-driven grain refinement at low temperatures,while deformation at high temperatures involved grain elongation along shear zones,enabling greater strain accommodation before material failure.展开更多
Tellurene,a chiral chain semiconductor with a narrow bandgap and exceptional strain sensitivity,emerges as a pivotal material for tailoring electronic and optoelectronic properties via strain engineering.This study el...Tellurene,a chiral chain semiconductor with a narrow bandgap and exceptional strain sensitivity,emerges as a pivotal material for tailoring electronic and optoelectronic properties via strain engineering.This study elucidates the fundamental mechanisms of ultrafast laser shock imprinting(LSI)in two-dimensional tellurium(Te),establishing a direct relationship between strain field orientation,mold topology,and anisotropic structural evolution.This is the first demonstration of ultrafast LSI on chiral chain Te unveiling orientation-sensitive dislocation networks.By applying controlled strain fields parallel or transverse to Te’s helical chains,we uncover two distinct deformation regimes.Strain aligned parallel to the chain’s direction induces gliding and rotation governed by weak interchain interactions,preserving covalent intrachain bonds and vibrational modes.In contrast,transverse strain drives shear-mediated multimodal deformations—tensile stretching,compression,and bending—resulting in significant lattice distortions and electronic property modulation.We discovered the critical role of mold topology on deformation:sharp-edged gratings generate localized shear forces surpassing those from homogeneous strain fields via smooth CD molds,triggering dislocation tangle formation,lattice reorientation,and inhomogeneous plastic deformation.Asymmetrical strain configurations enable localized structural transformations while retaining single-crystal integrity in adjacent regions—a balance essential for functional device integration.These insights position LSI as a precision tool for nanoscale strain engineering,capable of sculpting 2D material morphologies without compromising crystallinity.By bridging ultrafast mechanics with chiral chain material science,this work advances the design of strain-tunable devices for next-generation electronics and optoelectronics,while establishing a universal framework for manipulating anisotropic 2D systems under extreme strain rates.This work discovered crystallographic orientation-dependent deformation mechanisms in 2D Te,linking parallel strain to chain gliding and transverse strain to shear-driven multimodal distortion.It demonstrates mold geometry as a critical lever for strain localization and dislocation dynamics,with sharp-edged gratings enabling unprecedented control over lattice reorientation.Crucially,the identification of strain field conditions that reconcile severe plastic deformation with single-crystal retention offers a pathway to functional nanostructure fabrication,redefining LSI’s potential in ultrafast strain engineering of chiral chain materials.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the tem...The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.展开更多
The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Bas...The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Based on the experimental data,the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained.The apparent activation energy of deformation is calculated,which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90.The efficiency of power dissipation η changes obviously with the variation of deformation conditions.Under the strain rates of 0.01,0.1 and 1 s-（-1）,the value of η increases with increasing the true strain for different deformation temperatures.While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s-（-1）.The optimum processing condition is（t（opi）=1060℃,ε（opi）=0.1 s-（-1）） with the peak efficiency of 0.51.Under this deformation,dynamic recrystallization（DRX） is observed obviously in the microstructure of welding zone.Under the condition of 1060℃ and 0.001 s-（-1）,the deformation mechanism is dominated by dynamic recovery（DRV） and the value of η decreases sharply（η=0.02）.The flow instability is predicted to occur since the instability parameter ξ（ε）becomes negative.The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s-（-1） and the temperature of 900-1060℃.展开更多
Mechanical behavior of nickel？titanium shape memory alloy（NiTi SMA） under hot deformation was investigated according to the true stress—strain curves of NiTi samples under compression at the strain rates of 0.001-...Mechanical behavior of nickel？titanium shape memory alloy（NiTi SMA） under hot deformation was investigated according to the true stress—strain curves of NiTi samples under compression at the strain rates of 0.001-1 s-1 and at the temperatures of 600？1000℃.Dynamic recovery and dynamic recrystallization of NiTi SMA were systematically investigated by microstructural evolution.The influence of the strain rates,the deformation temperatures and the deformation degree on the dynamic recovery and dynamic recrystallization of NiTi SMA was obtained as well.NiTi SMA was characterized by the combination of dynamic recovery and dynamic recrystallization at 600℃ and 700℃,but the complete dynamic recrystallization occurred at other deformation temperatures.Increasing the deformation temperatures or decreasing the stain rates leads to larger equiaxed grains.The deformation degree has an important influence on the dynamic recrystallization of NiTi SMA.There exists the critical deformation degree during the dynamic recrystallization of NiTi SMA,beyond which the larger deformation degree contributes to obtaining the finer equiaxed grains.展开更多
The hot compression behavior of a wrought Mg-6Zn-1Al-0.3Mn magnesium alloy was investigated using Gleeble test at 200-400 °C with strain rates ranging from 0.01 to 7 s-1. The true stress-strain curves show that t...The hot compression behavior of a wrought Mg-6Zn-1Al-0.3Mn magnesium alloy was investigated using Gleeble test at 200-400 °C with strain rates ranging from 0.01 to 7 s-1. The true stress-strain curves show that the hot deformation behavior significantly depends on the deformation temperature and strain rate. The calculated hot deformation activation energy Q is 166 kJ/mol with a stress exponent n=5.99, and the constitutive equation is deduced to be ε＆ =3.16×1013[sinh（0.010σ）]5.99exp [-1.66×105/（RT）]· Deformation microstructure shows that the incompletely dynamically recrystallized grains can be found at grain boundaries and twins with the strain rates ranging from 0.01 to 1 s^-1 at 250 °C, and completely dynamic recrystallization occurs when the temperature is 350 °C or above during hot compression, the size of recrystallized grains decreases with the increment of the strain rate at the same temperature. The relatively suitable deformation condition is considered temperature 330-400 °C and strain rate of 0.01-0.03 s-1, and temperature of 350 °C and strain rate of 1 s-1.展开更多
The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ran...The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ranging from 0.001 to 10 s -1 .The steady flow stress increased with increasing the strain rate or decreasing the deformation temperature,which can be described by a hyperbolic-sine constitutive equation with the deformation activation energy of 150.25 kJ/mol.The tendency of dynamic recrystallization enhanced at high deforming temperatures and low strain rates,which corresponded to low Z values.With decreasing Z value,the main softening mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization, correspondingly,the subgrain size increased and the dislocation density decreased.展开更多
TA2 pure titanium was chosen to research the interaction among deformation, recrystallization and phase transformation during hot compression. The samples were hot compressed by thermal simulation method with differen...TA2 pure titanium was chosen to research the interaction among deformation, recrystallization and phase transformation during hot compression. The samples were hot compressed by thermal simulation method with different processing parameters. Variant selection induced by stress during cooling after compression was found. The prismatical texture component which featured that the [0001] direction perpendicular to the compressing direction produced preferentially under the compressing stress. As a result, the transformedα phase possesses strong prismatical texture which is different with the basal texture of compressed αphase. The minimum elastic strain energy is demonstrated to be the main reason that causes the variant selection. Dynamic recrystallization behavior and microstructure evolution during hot compression were also studied.展开更多
Micro radial compression tests were carried out on cylindrical specimens of pure copper polycrystals with different grain sizes. Experimental results indicated that phenomena of decreasing forming force, increasing sc...Micro radial compression tests were carried out on cylindrical specimens of pure copper polycrystals with different grain sizes. Experimental results indicated that phenomena of decreasing forming force, increasing scatter of forming force and more irregular surface topography occurred with the increase of grain size. A modified surface model based on dislocations pile-up in surface layer grains, and a flow stress scattering formulation based on standard deviation and grain size distribution were proposed to analyze size effects on forming force in micro compression. The inhomogeneous deformation of surface layer grains was discussed by the main deformation manner of rotation. A good agreement with the experimental results was achieved.展开更多
The flow behavior and microstructure evolution of 6A82 aluminum alloy (Al?Mg?Si?Cu) with high copper content were studied on a Gleeble?1500 system by isothermal hot compression test in the temperature range from 320 t...The flow behavior and microstructure evolution of 6A82 aluminum alloy (Al?Mg?Si?Cu) with high copper content were studied on a Gleeble?1500 system by isothermal hot compression test in the temperature range from 320 to 530 °C and the strain rate range from 0.001 to 10 s?1. The results reveal that the flow stress of the alloy exhibits a continuous flow softening behavior at low temperatures of 320?390 °C, whereas it reaches steady state at high temperatures (≥460°C), which are influenced greatly by the Zener?Hollomon parameter (Z) in the hyperbolic sine with the hot deformation activation energy of 325.12 kJ/mol. Microstructure characterizations show that prominent dynamic recrystallization and coarsening of dynamic precipitation may be responsible for the continuous flow softening behavior. Due to deformation heating at high strain rates (≥1 s?1), dynamic recrystallization is more prominent in the specimen deformed at 530 °C and 10 s?1 than in the specimen deformed at 460 °C and 0.1 s?1 even though they have very close lnZ values.展开更多
The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction（XRD）, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. And, compression...The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction（XRD）, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. And, compression deformation behavior at room-temperature was studied. The results showed that the microstructure of Mg-8Zn-1Y alloy solidified under ambient pressure and super-high pressure was both mainly composed of ■-Mg and quasicrystal I-Mg3Zn6 Y. Solidification under super-high pressure contributed to refining solidified microstructure and changing morphology of the intergranular second phase. The morphology of intergranular second phase（quasicrystal I-Mg3Zn6Y） was transformed from continuous network（ambient pressure） to long island（high pressure） and finally to granular（super-high pressure） with the increase in pressure. The compressive strength, yield strength and rupture strain of the samples solidified under ambient pressure were significantly improved from 262.6 MPa, 244.4 MPa and 13.3% to 437.3 MPa, 368.9 MPa and 24.7% under the pressure of 6 GPa, respectively. Under ambient pressure, cleavage plane on compressive fracture was large and smooth. When it was solidified under the pressure ranging from 4 to 6 GPa, cleavage plane on compressive fracture was small and coarse. In addition, dimple, tear ridge and lobate patterns existed.展开更多
基金National Natural Science Foundation of China(52305349)Heilongjiang Touyan Team(HITTY-20190036)+2 种基金Heilongjiang Provincial Natural Science Foundation of China(LH2023E033)CGN-HIT Advanced Nuclear and New Energy Research Institute(CGN-HIT202305)Natural Science Basic Research Program of Shaanxi Province(2023-JC-QN-0518)。
文摘The effect of deformation resistance of AlCr_(1.3)TiNi_(2) eutectic high-entropy alloys under various current densities and strain rates was investigated during electrically-assisted compression.Results show that at current density of 60 A/mm^(2) and strain rate of 0.1 s^(−1),the ultimate tensile stress shows a significant decrease from approximately 3000 MPa to 1900 MPa with reduction ratio of about 36.7%.However,as current density increases,elongation decreases due to intermediate temperature embrittlement.This is because the current induces Joule effect,which then leads to stress concentration and more defect formation.Moreover,the flow stress is decreased with the increase in strain rate at constant current density.
基金fnancially supported by the Scientifc Research Project of the Department of Education in Hunan Prov ince,China(Grant No.23B0533).
文摘In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).
基金supported by the National Key Research and Development Program of China(No.2022YFC2903903)the National Natural Science Foundation of China(No.52374157)+1 种基金the General Project of National Natural Science Foundation of China(No.52374157)Ordos Major Science and Technology Program(No.JBGS-2023-003)。
文摘This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities,combined with digital speckle and acoustic emission(AE)monitoring.The results show that as the dip angle of the primary joint increases,the failure mode transitions from overall failure to wedge block ejection and shear failure.A failure mode identification model was established based on main crack dip angle thresholds(40°,45°),uniaxial compressive strength thresholds(40,90 MPa),and energy core zone proportion thresholds(20%,10%),achieving an accuracy of 93.3%.In the overall failure and wedge block ejection modes,a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase(>0.6σ_(c)),while in the shear failure mode,significant fluctuations are observed due to the shear-tension alternation,making it difficult to identify a single critical point.Additionally,joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase(>0.8σ_(c)).These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.
基金supported by the Natural Science Foundation of Heilongjiang Province,China(No.LH2021E051)the National Natural Science Foundation of China(No.52204386)Outstanding Youth Science Fund of Heilongjiang,China(No.JQ2023E003).
文摘The regulation of martensitic transformation and intrinsic brittleness are critical issues for the application of Ni-Mn-Ga shape memory alloys,and they are closely related to the alloy composition andγphase.In this study,single and dual-phase Ni_(55+x)Mn_(25)Ga_(20-x)(x=0,2,4 and 6)alloys were fabricated.The proportion of theγphase was elevated gradually,and the peak martensitic transformation temperature was enhanced from 350 to 460℃ with an increasing Ni/Ga ratio.The microstructures of theγphase were further regulated from continuous block to dispersed granular after annealing.The annealed dual-phase alloy with x=2 exhibited greater yield stress,compressive strength and toughness than the annealed single-phase alloy.It maintained plastic deformation without fracture,even at a strain of 30%.High strain energy and dislocation density were observed in the martensite of the dual-phase alloy,which can be attributed toγphases and the interface between martensite andγphases.Furthermore,[001]-oriented martensite variants were obtained during deformation in the dual-phase alloy.They were parallel to the loading direction and conducive to improving the compressive strength.This protocol provides in-depth insight into the influence of theγphase on the texture evolution and mechanical behavior of martensite during deformation.
基金Project(52274369)supported by the National Natural Science Foundation of China。
文摘High-purity silver(Ag)is extensively utilized in electronics,aerospace,and other advanced industries due to its excellent thermal conductivity,electrical conductivity,and machinability.However,the prohibitive material cost poses substantial challenges for optimizing thermal processing parameters through repetitive experimental trials.In this work,hot compression experiments on high-purity silver were conducted using a Gleeble-3800 thermal simulator.The high temperature deformation behaviors,dynamic recovery(DRV)and dynamic recrystallization(DRX)of high-purity silver were studied by constructing an Arrhenius constitutive equation and developing thermal processing maps.The results show that plastic instability of high-purity silver occurs at high strain rates and the optimized hot processing parameters are the strain rate below 0.001 s^(−1) and the temperature of 340−400℃.Microstructural observations exhibit that DRV prefers to occur at lower deformation temperatures(e.g.,250℃).This is attributed to the low stacking fault energy of high-purity silver,which facilitates the decomposition of dislocations into partial dislocations and promotes high-density dislocation accumulation.Furthermore,DRX in high-purity silver becomes increasingly pronounced with increasing deformation temperature and reaches saturation at 350℃.
基金financially supported by the Fundamental Research Funds for the Central Universities,China(No.2023JCCXNY01)Guangxi Key Technologies R&D Program,China(No.2022AB31022).
文摘The backfill should keep stable in the primary stope when mining an adjacent secondary stope in subsequent open stoping mining methods,and the large-size mined-out area is usually backfilled by multiple backfilling before the recovery of a secondary stope,resulting in a layered structure of backfill in stope.Therefore,it is significant to investigate the deformation responses and mechanical properties of stratified cemented tailings backfill(SCTB)with different layer structures to remain self-standing as an artificial pillar in the primary stope.The current work examined the effects of enhance layer position(1/3,1/2,and 2/3)and thickness ratio(0,0.1,0.2,and 0.3)on the mechanical properties,deformation,energy evolution,microstructures,and failure modes of SCTB.The results demonstrate that the incorporation of an enhance layer significantly strengthens the deformation and strength of SCTB.Under a confining pressure of 50 kPa,the peak deviatoric stress rises from 525.6 to 560.3,597.1,and 790.5 kPa as the thickness ratio of enhance layer is increased from 0 to 0.1,0.2,and 0.3,representing a significant increase of 6.6%,13.6%,and 50.4%.As the confining pressure increases,the slopes of the curves in the elastic stage become steep,and the plastic phase is extended accordingly.Additionally,the incorporation of the enhance layer significantly improves the energy storage linit of SCTB specimen.As the thickness ratio of the enhance layer increases from 0 to 0.1,0.2,and 0.3,the elastic energy rises from 0.54 to 0.67,0.84,and 1.00 MJ·m^(-3),representing a significant increase of 24.1%,55.6%,and 85.2%.The internal friction angles and cohesions of the SCTB specimens are higher than those of the CTB specimens,however,the cohesion is more susceptible to enhance layer position and thickness ratio than the internal friction angle.The failure style of the SCTB specimen changes from shear failure to splitting bulging failure and shear bulging failure with the presence of an enhance layer.The crack propagation path is significantly blocked by the enhance layer.The findings are of great significance to the application and stability of the SCTB in subsequent stoping backfilling mines.
基金supported by the National Natural Science Foundation of China(Nos.12072105,11932006,and 52474388).
文摘The applications of Al alloy foam require consideration of potential damage risks,which are closely related to the evolution of its internal pore structures.However,conventional ex situ experimental observation cannot provide information on the structure evolution during deformation.In order to investigate the failure mechanism of Al alloy foam under quasi-static compression,by utilizing X-ray imaging technology,in situ CT image data were obtained during the loading process.A geometric model characterizing the real structure of Al alloy foam was reconstructed from the initial CT images and used for finite element simulation.Besides,based on the digital volume correlation(DVC)method,the displacement and strain fields of Al alloy foam were calculated.The results show that the in situ experimental observation based on X-ray imaging can effectively obtain the failure information of Al alloy foam.The simulation results for deformation and failure behavior of Al alloy foam are consistent with experimental results.During the quasi-static compression,a shear band can be observed diagonally across the profile of Al alloy foam,with weak regions occurring in the cells with larger volume and higher aspect ratios.Using these weak regions as boundaries,the relative displacement of cell structures on one side compared to another side was identified as the intrinsic cause of shear band formation.The high-strain regions identified by DVC closely match the crack locations on the cell walls,validating the accuracy of DVC on localizing cracks on cell walls and predicting their propagation trends.
基金supported by the National Natural Science Foundation of China(52174361,52074114)Science and Technology Innovation Program of Hunan Province(2023RC3106)+2 种基金Open Fund of the China Spallation Neutron Source Songshan Lake Science City(KFKT2023B13)Graduate Training and Innovation Practice Base of Hunan Province,China Scholarship Council(202106130051)Postgraduate Scientific Research Innovation Project of Hunan Province(QL20220100,QL20230094).
文摘Multi-pass hot processing methods are commonly used in magnesium(Mg)alloys to overcome the poor workability due to limited slip systems,which generally involve complicated post-deformation softening and hardening behaviors.In this work,to reveal post-deformation softening and hardening mechanisms of a Mg-2Y-1Zn alloy,double-stage hot compression tests and microstructural observations were conducted.The results showed that the softening fraction of Mg-2Y-1Zn alloy showed a non-linear dependence on deformation conditions and could be general coupled by Z parameter.Due to the formation and cross-overlapping of twins and kinks,only static recovery(SRV)occurred during holding process at 300℃/0.001 s^(-1) which led to the least static softening:5.52% after 10 s of holding.For samples at 400℃/0.001s^(-1),the enhanced post-deformation softening,which is 11.93% after 10 s of holding,was attributed to static recrystallization(SRX)followed continuous dynamic recrystallization(CDRX)happened during first deformation stage as well as SRV influenced by the LPSO phases.Under deformation condition of 400℃/0.1 s^(-1),the coupled meta-dynamic recrystallization(MDRX)and SRX resulted in serious stress relaxation,which is 42.83% after 10 s of holding,and caused hardening phenomenon at reloading stage.The 18R-LPSO and 14H-LPSO phases synchronously worked on deformation behaviors and limited the growth of recrystallized grains.Further,a simplified static softening kinetics model was established based on Johnson-Mehl-Avrami-Kolmogorov equation and employed to rationalize experimental data.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea Program(No.RS-2025-02603127,Innovation Research Center for Zero-carbon Fuel Gas Turbine Design,Manufacture,and Safety)。
文摘Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector.This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under uniaxial tension along rolling direction(RD)and transverse direction(TD)at-50,25,50,and 150℃.Results reveal a transition from high strength with limited elongation at-50℃ to significant softening and maximum ductility at 150℃.TD samples consistently showed 2%-6%higher strength than RD;however,this yield anisotropy diminished at 150℃ due to the shift from twinning to thermally activated slip and recovery.Fractography indicated a change from semi-brittle to fully ductile fracture with increasing temperature.Electron backscattered diffraction(EBSD)analysis confirmed twinning-driven grain refinement at low temperatures,while deformation at high temperatures involved grain elongation along shear zones,enabling greater strain accommodation before material failure.
基金financial support from NSF ExpandQISE program.The synthesis of tellurene was supported by NSF under grant no.CMMI-2046936supports from Purdue Research Foundation.
文摘Tellurene,a chiral chain semiconductor with a narrow bandgap and exceptional strain sensitivity,emerges as a pivotal material for tailoring electronic and optoelectronic properties via strain engineering.This study elucidates the fundamental mechanisms of ultrafast laser shock imprinting(LSI)in two-dimensional tellurium(Te),establishing a direct relationship between strain field orientation,mold topology,and anisotropic structural evolution.This is the first demonstration of ultrafast LSI on chiral chain Te unveiling orientation-sensitive dislocation networks.By applying controlled strain fields parallel or transverse to Te’s helical chains,we uncover two distinct deformation regimes.Strain aligned parallel to the chain’s direction induces gliding and rotation governed by weak interchain interactions,preserving covalent intrachain bonds and vibrational modes.In contrast,transverse strain drives shear-mediated multimodal deformations—tensile stretching,compression,and bending—resulting in significant lattice distortions and electronic property modulation.We discovered the critical role of mold topology on deformation:sharp-edged gratings generate localized shear forces surpassing those from homogeneous strain fields via smooth CD molds,triggering dislocation tangle formation,lattice reorientation,and inhomogeneous plastic deformation.Asymmetrical strain configurations enable localized structural transformations while retaining single-crystal integrity in adjacent regions—a balance essential for functional device integration.These insights position LSI as a precision tool for nanoscale strain engineering,capable of sculpting 2D material morphologies without compromising crystallinity.By bridging ultrafast mechanics with chiral chain material science,this work advances the design of strain-tunable devices for next-generation electronics and optoelectronics,while establishing a universal framework for manipulating anisotropic 2D systems under extreme strain rates.This work discovered crystallographic orientation-dependent deformation mechanisms in 2D Te,linking parallel strain to chain gliding and transverse strain to shear-driven multimodal distortion.It demonstrates mold geometry as a critical lever for strain localization and dislocation dynamics,with sharp-edged gratings enabling unprecedented control over lattice reorientation.Crucially,the identification of strain field conditions that reconcile severe plastic deformation with single-crystal retention offers a pathway to functional nanostructure fabrication,redefining LSI’s potential in ultrafast strain engineering of chiral chain materials.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金Project (51005112) supported by the National Natural Science Foundation of ChinaProject (2010ZF56019) supported by the Aviation Science Foundation of China+1 种基金Project (GJJ11156) supported by the Education Commission of Jiangxi Province, ChinaProject(GF200901008) supported by the Open Fund of National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology, China
文摘The high temperature deformation behaviors of α＋β type titanium alloy TC11 （Ti-6.5Al-3.5Mo-1.5Zr-0.3Si） with coarse lamellar starting microstructure were investigated based on the hot compression tests in the temperature range of 950-1100 ℃ and the strain rate range of 0.001-10 s-1. The processing maps at different strains were then constructed based on the dynamic materials model, and the hot compression process parameters and deformation mechanism were optimized and analyzed, respectively. The results show that the processing maps exhibit two domains with a high efficiency of power dissipation and a flow instability domain with a less efficiency of power dissipation. The types of domains were characterized by convergence and divergence of the efficiency of power dissipation, respectively. The convergent domain in a＋fl phase field is at the temperature of 950-990 ℃ and the strain rate of 0.001-0.01 s^-1, which correspond to a better hot compression process window of α＋β phase field. The peak of efficiency of power dissipation in α＋β phase field is at 950 ℃ and 0.001 s 1, which correspond to the best hot compression process parameters of α＋β phase field. The convergent domain in β phase field is at the temperature of 1020-1080 ℃ and the strain rate of 0.001-0.1 s^-l, which correspond to a better hot compression process window of β phase field. The peak of efficiency of power dissipation in ℃ phase field occurs at 1050 ℃ over the strain rates from 0.001 s^-1 to 0.01 s^-1, which correspond to the best hot compression process parameters of ,8 phase field. The divergence domain occurs at the strain rates above 0.5 s^-1 and in all the tested temperature range, which correspond to flow instability that is manifested as flow localization and indicated by the flow softening phenomenon in stress-- strain curves. The deformation mechanisms of the optimized hot compression process windows in a＋β and β phase fields are identified to be spheroidizing and dynamic recrystallizing controlled by self-diffusion mechanism, respectively. The microstructure observation of the deformed specimens in different domains matches very well with the optimized results.
基金Project(51175431)supported by the National Natural Science Foundation of China
文摘The high-temperature flow behavior of TCll/Ti-22Al-25 Nb electron beam（EB） weldments was investigated by the isothermal compression tests at the temperature of 900-1060℃ and the strain rate of 0.001-10 s-（-1）.Based on the experimental data,the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained.The apparent activation energy of deformation is calculated,which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90.The efficiency of power dissipation η changes obviously with the variation of deformation conditions.Under the strain rates of 0.01,0.1 and 1 s-（-1）,the value of η increases with increasing the true strain for different deformation temperatures.While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s-（-1）.The optimum processing condition is（t（opi）=1060℃,ε（opi）=0.1 s-（-1）） with the peak efficiency of 0.51.Under this deformation,dynamic recrystallization（DRX） is observed obviously in the microstructure of welding zone.Under the condition of 1060℃ and 0.001 s-（-1）,the deformation mechanism is dominated by dynamic recovery（DRV） and the value of η decreases sharply（η=0.02）.The flow instability is predicted to occur since the instability parameter ξ（ε）becomes negative.The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s-（-1） and the temperature of 900-1060℃.
基金Project(51071056) supported by the National Natural Science Foundation of ChinaProjects(HEUCFR1132,HEUCF121712) supported by the Fundamental Research Funds for the Central Universities of China
文摘Mechanical behavior of nickel？titanium shape memory alloy（NiTi SMA） under hot deformation was investigated according to the true stress—strain curves of NiTi samples under compression at the strain rates of 0.001-1 s-1 and at the temperatures of 600？1000℃.Dynamic recovery and dynamic recrystallization of NiTi SMA were systematically investigated by microstructural evolution.The influence of the strain rates,the deformation temperatures and the deformation degree on the dynamic recovery and dynamic recrystallization of NiTi SMA was obtained as well.NiTi SMA was characterized by the combination of dynamic recovery and dynamic recrystallization at 600℃ and 700℃,but the complete dynamic recrystallization occurred at other deformation temperatures.Increasing the deformation temperatures or decreasing the stain rates leads to larger equiaxed grains.The deformation degree has an important influence on the dynamic recrystallization of NiTi SMA.There exists the critical deformation degree during the dynamic recrystallization of NiTi SMA,beyond which the larger deformation degree contributes to obtaining the finer equiaxed grains.
基金Project(2011BAE22B01-1)supported by the National Key Technologies R&D Program of ChinaProject(2011DFA50903)supported by the International S&T Cooperation Program of China
文摘The hot compression behavior of a wrought Mg-6Zn-1Al-0.3Mn magnesium alloy was investigated using Gleeble test at 200-400 °C with strain rates ranging from 0.01 to 7 s-1. The true stress-strain curves show that the hot deformation behavior significantly depends on the deformation temperature and strain rate. The calculated hot deformation activation energy Q is 166 kJ/mol with a stress exponent n=5.99, and the constitutive equation is deduced to be ε＆ =3.16×1013[sinh（0.010σ）]5.99exp [-1.66×105/（RT）]· Deformation microstructure shows that the incompletely dynamically recrystallized grains can be found at grain boundaries and twins with the strain rates ranging from 0.01 to 1 s^-1 at 250 °C, and completely dynamic recrystallization occurs when the temperature is 350 °C or above during hot compression, the size of recrystallized grains decreases with the increment of the strain rate at the same temperature. The relatively suitable deformation condition is considered temperature 330-400 °C and strain rate of 0.01-0.03 s-1, and temperature of 350 °C and strain rate of 1 s-1.
基金Project(2012CB619503)supported by the High-tech Research and Development Program of China
文摘The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ranging from 0.001 to 10 s -1 .The steady flow stress increased with increasing the strain rate or decreasing the deformation temperature,which can be described by a hyperbolic-sine constitutive equation with the deformation activation energy of 150.25 kJ/mol.The tendency of dynamic recrystallization enhanced at high deforming temperatures and low strain rates,which corresponded to low Z values.With decreasing Z value,the main softening mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization, correspondingly,the subgrain size increased and the dislocation density decreased.
文摘TA2 pure titanium was chosen to research the interaction among deformation, recrystallization and phase transformation during hot compression. The samples were hot compressed by thermal simulation method with different processing parameters. Variant selection induced by stress during cooling after compression was found. The prismatical texture component which featured that the [0001] direction perpendicular to the compressing direction produced preferentially under the compressing stress. As a result, the transformedα phase possesses strong prismatical texture which is different with the basal texture of compressed αphase. The minimum elastic strain energy is demonstrated to be the main reason that causes the variant selection. Dynamic recrystallization behavior and microstructure evolution during hot compression were also studied.
基金Project(51375113)supported by the National Natural Science Foundation of China
文摘Micro radial compression tests were carried out on cylindrical specimens of pure copper polycrystals with different grain sizes. Experimental results indicated that phenomena of decreasing forming force, increasing scatter of forming force and more irregular surface topography occurred with the increase of grain size. A modified surface model based on dislocations pile-up in surface layer grains, and a flow stress scattering formulation based on standard deviation and grain size distribution were proposed to analyze size effects on forming force in micro compression. The inhomogeneous deformation of surface layer grains was discussed by the main deformation manner of rotation. A good agreement with the experimental results was achieved.
基金Project(2014DFA51270)supported by the International Science and Technology Cooperation Program of ChinaProject(CDJRC10130008)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(51421001)supported by the National Natural Science Foundation of China
文摘The flow behavior and microstructure evolution of 6A82 aluminum alloy (Al?Mg?Si?Cu) with high copper content were studied on a Gleeble?1500 system by isothermal hot compression test in the temperature range from 320 to 530 °C and the strain rate range from 0.001 to 10 s?1. The results reveal that the flow stress of the alloy exhibits a continuous flow softening behavior at low temperatures of 320?390 °C, whereas it reaches steady state at high temperatures (≥460°C), which are influenced greatly by the Zener?Hollomon parameter (Z) in the hyperbolic sine with the hot deformation activation energy of 325.12 kJ/mol. Microstructure characterizations show that prominent dynamic recrystallization and coarsening of dynamic precipitation may be responsible for the continuous flow softening behavior. Due to deformation heating at high strain rates (≥1 s?1), dynamic recrystallization is more prominent in the specimen deformed at 530 °C and 10 s?1 than in the specimen deformed at 460 °C and 0.1 s?1 even though they have very close lnZ values.
基金Project supported by National Natural Science Foundation of China(51475486)Natural Science Foundation of Hebei Province(E2013501096)
文摘The microstructure of Mg-8Zn-1Y alloy solidified under super-high pressure was analyzed through X-ray diffraction（XRD）, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. And, compression deformation behavior at room-temperature was studied. The results showed that the microstructure of Mg-8Zn-1Y alloy solidified under ambient pressure and super-high pressure was both mainly composed of ■-Mg and quasicrystal I-Mg3Zn6 Y. Solidification under super-high pressure contributed to refining solidified microstructure and changing morphology of the intergranular second phase. The morphology of intergranular second phase（quasicrystal I-Mg3Zn6Y） was transformed from continuous network（ambient pressure） to long island（high pressure） and finally to granular（super-high pressure） with the increase in pressure. The compressive strength, yield strength and rupture strain of the samples solidified under ambient pressure were significantly improved from 262.6 MPa, 244.4 MPa and 13.3% to 437.3 MPa, 368.9 MPa and 24.7% under the pressure of 6 GPa, respectively. Under ambient pressure, cleavage plane on compressive fracture was large and smooth. When it was solidified under the pressure ranging from 4 to 6 GPa, cleavage plane on compressive fracture was small and coarse. In addition, dimple, tear ridge and lobate patterns existed.
