The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a...The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a temperature of 900℃.True flow stress-strain curves were determined for 600℃–900℃and used to construct a Hensel-Spittel model for FEM simulation.The process parameters,i.e.,stress,temperature,imposed strain,and force,were investigation during the rotary swaging process.Firstly,the stresses induced during rotary swaging and the resistance of the material to deformation were investigated.The amount and distribution of imposed strain in the cross-section can serve as a valuable indicator of the reduction in porosity and the texture evolution of the material.The simulation revealed the force required to swag the Dievar alloy.It also showed the evolution of temperature,which is important for phase transformation during solidification.Furthermore,microstructure evolutionwas observed before and then after rotary swaging.Dievar alloy is a critical material in the manufacture of dies for high-pressure die casting,forging tools,and other equipment subjected to high temperatures and mechanical loads.Understanding its viscoelastoplastic behavior under rotary swaging conditions is essential to optimize its performance in these demanding industrial applications.展开更多
A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the form...A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the formation of a recrystallized microstructure after RS with a grain size of 3.2±0.2μm leads to an increase in the strength of the alloy without reduction of level of ductility and corrosion resistance.At the same time,aging of the quenched alloy at 100℃ for 8 h leads to a slight increase in strength,but significantly reduces its ductility and corrosion resistance.The study of the degradation process of the alloy in the quenched state and after RS,both under in vitro and in vivo conditions,did not reveal a significant difference between these two microstructural states.However,an increase in the duration of incubation of the alloy in a complete growth medium from 4 h to 24 days leads to a decrease in the degradation rate(DR)by 4times(from~2 to~0.5 mm/year)due to the formation of a dense layer of degradation products.The study of biocompatibility in vitro did not reveal a significant effect of RS on the hemolytic and cytotoxic activity of the alloy.No signs of systemic toxicity were observed after subcutaneous implantation of alloy samples into mice before and after RS.However,it was found that RS promotes uniform degradation of the alloy over the entire contact surface.In summary,RS at 350℃ allows to increase the strength of Mg-1%Zn-0.6%Ca alloy up to348±5 MPa at a ductility level of 17.3±2.8%and a DRin vivoequal to 0.56±0.12 mm/year without impairing its biocompatibility in vitro and in vivo.展开更多
A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging...A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.展开更多
A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compressi...A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compression yield asymmetry,compared with that prepared via room-temperature rotary swaging.Transmission electron microscopy investigations showed that at the initial stage,multiple twins,mostly tension twins,were activated and intersected with each other,thereby refining the coarse grains into a fine lamellar structure.Then,two types of nanoscale subgrains were generated with increasing swaging strain.The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries.This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress.The second type of nanoscale subgrain was formed within the twin lamellae.The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays.Finally,randomly oriented nanograins were obtained via dynamic recrystallization,under the combined function of deformation heat and increased stored energy.Compared with room-temperature rotary swaging,cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.展开更多
Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed...Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.展开更多
Rotary swaging(RS)of alloy Mg-1.03Zn-0.66Ca(ZX11)was shown to refine the average grain size to 4.5±1.2μm in a longitudinal section and 4.8±0.9μm in a transverse section.In addition,a small amount of Mg2Ca ...Rotary swaging(RS)of alloy Mg-1.03Zn-0.66Ca(ZX11)was shown to refine the average grain size to 4.5±1.2μm in a longitudinal section and 4.8±0.9μm in a transverse section.In addition,a small amount of Mg2Ca particles about 300nm in size and Mg6Zn3Ca2 particles with a size of about lOOnm was detected.This resulted in pronounced strengthening:the yield strength and the ultimate tensile strength rose to 210±8 MPa and 276±6 MPa,respectively,while the elongation hardly decreased(22.0±1.8% and 18.3±2.9% before and after RS).Furthermore,RS led to an increase in the fatigue limit of the alloy from 120 MPa to 135 MPa and did not impair its resistance to chemical corrosion.The studies in vitro showed that ZX11 induces hemolysis without inhibiting the viability of peripheral blood mononuclear cells and has a more pronounced cytotoxic effect on tumor cells in comparison with non-transformed cells.No significant difference of the latter effect between the initial and the deformed states was observed.展开更多
Tensile behavior of an equiaxed-grained Fe-6.5 wt.%Si alloy,which was deformed intoφ6 mm bar by hot rotary swaging,was investigated at various temperatures(300–400℃)and stretching rates(0.42–1 mm/min).The results ...Tensile behavior of an equiaxed-grained Fe-6.5 wt.%Si alloy,which was deformed intoφ6 mm bar by hot rotary swaging,was investigated at various temperatures(300–400℃)and stretching rates(0.42–1 mm/min).The results revealed an enhancement in the intermediate-temperature tensile ductility after heat treatments.Deformation twinning was found in the equiaxed-grained Fe-6.5 wt.%Si bars during the tensile test,and heat treatments can enhance the deformation twinning.More twins can be observed in the necking areas than other regions.The high Schmid factor values above 0.4 after heat treatments demonstrated that deformation twinning can easily occur in the equiaxed-grained Fe-6.5 wt.%Si alloy.Higher deformation temperatures,higher strain rates,and larger degree of order suppressed the formation of deformation twinning,while the grain sizes had little effect on the deformation twinning.The twinning stress of the Fe-6.5 wt.%Si alloy increased with the increasing grain size,which did not agree with the Hall–Petch type relationship.The deformation twinning resulted in the improved ductility of the Fe-6.5 wt.%Si alloy.展开更多
In this paper,an elasto-viscoplastic three-dimension(3D) finite element model is developed to simulate the processing of bimetal tube with rotary swaging. Through simulation,the effects of high-frequency pulse strokin...In this paper,an elasto-viscoplastic three-dimension(3D) finite element model is developed to simulate the processing of bimetal tube with rotary swaging. Through simulation,the effects of high-frequency pulse stroking on the distribution and histories of stress,stain and loading are clarified. The stress in inner tube is compressive and higher than the minimum bonding force. Meanwhile,the stiffness of inner tube impacts outer tube extension in length.展开更多
This paper presents the parametric analysis conducted to derive the optimal dimensions of the steel sleeve necessary to secure the bond performance of the swaging type anchorage for CFRP tendon with diameter of 5 mm. ...This paper presents the parametric analysis conducted to derive the optimal dimensions of the steel sleeve necessary to secure the bond performance of the swaging type anchorage for CFRP tendon with diameter of 5 mm. To that goal, finite element analysis is performed on the parameters determining the dimensions of the sleeve like the thickness and inner diameters of the sleeve. The results show that a constant swaging pressure of about 450 MPa on the mean is distributed in the sleeve when the thickness ratio of the stress relief zone to the effective swaging zone of the sleeve is larger than 1.1 and that the swaging pressure tends to reduce linearly as much as this thickness ratio becomes smaller than 1.1. The pressure varies within a range of about 30% according to the change in the inner diameter of the sleeve whereas varies within a range less than 10% according to the change in the inner diameter when the thickness ratio is larger than 1.1. Finally, the optimal dimensions of the steel tube sleeve enabling to secure an anchor force larger than the rupture strength of the CFRP tendon with diameter of 5 mm are determined based upon the results of the parametric analysis.展开更多
The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7...The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7)Se_(0.3) material with a certain textured structure is prepared by an innovative rotary swag-ing method.It is found that various defects including Te vacancies,dislocations,and grain boundaries significantly strengthen the phonon scattering.With an obviously suppressed thermal conductivity and well-maintained carrier mobility,the obtained rods extending up to several tens of centimeters achieve a peak ZT of 1.2 at 450 K and an average ZT of 1.0(300-550 K),with Vickers hardness and compressive strength increased to 0.42 GPa and 52.6 MPa,respectively.Moreover,the assembled 17-pair thermoelec-tric module achieves a competitive conversion efficiency of up to 6.3% and a high output power of 0.93 W at a temperature difference of 250 K.This study develops an effective strategy for synergistically en-hancing the thermoelectric and mechanical properties of n-type Bi_(2)(Te,Se)_(3).展开更多
Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employ...Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employing rotary swaging(RS),bulk NC Cu–15 at.%Al alloys with both high strength and high thermal stability were prepared.Quasi-static tensile test results show that the yield strength is 1016 MPa.Moreover,the grain growth temperature was retarded up to 0.4 Tm,higher than the literature values.Microstructural characterizations revealed that after RS deformation,coarse-grained Cu–Al was refined into fibrous NC grains with a diameter of 45 nm and a length of 190 nm,and the contents of high-angle grain boundaries(GBs),low-angle GBs,and twin boundaries are 17%,45%,and 38%,respectively.Moreover,there is a significant multiscale chemical fluctuation within the grains,at the GBs,and between the grains through extreme defect accumulation.The atomistic simulation suggests that the segregation behavior of Al solute is essentially driven by the atomic size and local stress state.Besides,Al segregation greatly reduces the grain boundary energy,which further improves the thermal stability of the material.The main strengthening mechanism is Hall–Petch strengthening and the strengthening brought by the chemical fluctuations.Our work provides ideas for designing strong and thermally stable bulk NC alloys.展开更多
Pure tungsten （PW） and W-1 wt% La203 （WL10） were prepared by powder metallurgical route fol- lowed by the swaging ＋ rolling process. The logarithmic strains are 0, 0.37, 0.58, and 0.98 for WL10 and 0, 0.58 for PW...Pure tungsten （PW） and W-1 wt% La203 （WL10） were prepared by powder metallurgical route fol- lowed by the swaging ＋ rolling process. The logarithmic strains are 0, 0.37, 0.58, and 0.98 for WL10 and 0, 0.58 for PW. Heat treatments were performed at temperatures var- ied from 1,573 to 2,173 K to determine the recrystalliza- tion temperature. Recrystallization temperatures are 1,973 and 2,173 K for WL1 （logarithmic strain of 0.37） and WL3 （logarithmic strain of 0.98）, respectively. But in the case of WL2 （logarithmic strain of 0.58）, full recrystallization is not achieved at temperature of above 2,173 K. Further- more, the recrystallization temperature of PW with loga- rithmic strain of 0.58 is at least 300 K lower than that of the equivalent WLI0 sample. Moreover, the increase of recrystallization temperature inhibits the strength degra- dation of WL2： samples lose 4 % and 22 % strength when annealed at 1,573 and 1,973 K compared with room tem- perature （RT） sample. Finally, the texture evolution for the swaged ＋ rolled WL10 is significantly related to the deformation degree： the dominated orientation is （001） for WL2 while （110） for WL3.展开更多
The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on ...The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on microstructures and mechanical properties were investigated using the SEM, TEM, OM and the universal material testing machine. Results show that the alloy can be easily hot forged and cold swaged due to the fine-grained microstructure. Only after cold swaging by 85%, the alloy shows the typical ＂marble-like＂ structure. And thecold deformation is accompanied by stress-induced a＂ phase transformations. Moreover, both the strength and the ductility of the alloy are significantly improved by hot and cold working.展开更多
The influence of hot swaging（SW） and annealing treatment on microstructure and mechanical properties of commercially pure titanium produced by investment casting was evaluated.The as-cast samples showed a typical mi...The influence of hot swaging（SW） and annealing treatment on microstructure and mechanical properties of commercially pure titanium produced by investment casting was evaluated.The as-cast samples showed a typical microstructure consisting of a variety of α-morphologies,while the hot swaged samples exhibited a kinked lamellar microstructure.Annealing at 500 °C did not significantly change this microstructure while annealing at 700 and 870 °C led to recrystallization and formation of equiaxed microstructures.The cast bars exhibited a typical hard α-layer in near-surface regions with a maximum depth and maximum hardness of 720 μm and HV0.5 660,respectively.Due to SW,the tensile strength of the as-cast material drastically increased from 605 MPa to 895 MPa.Annealing at 500 °C decreased the tensile strength slightly from 895 to 865 MPa while annealing at 700 °C led to a further pronounced drop in tensile strength from 865 to 710 MPa.No additional decrease in tensile strength was noticed with increasing the annealing temperature from 700 to 870 °C.The true fracture strain of the as-cast and hot swaged samples was in the range of 0.05 to 0.12,while the annealed samples showed values in the range of 0.25 to 0.53.In addition,the as-cast and hot swaged samples revealed a brittle cleavage fracture surfaces.However,the annealed samples showed a transgranular ductile fracture with formation of dimples.展开更多
Overstraining gun tubes has a twofold advantage. First, it enables the increase of the Safe Maximum Pressure(SMP) in the tube, resulting in a higher muzzle velocity which extends the gun's range and its projectile...Overstraining gun tubes has a twofold advantage. First, it enables the increase of the Safe Maximum Pressure(SMP) in the tube, resulting in a higher muzzle velocity which extends the gun's range and its projectile kinetic energy. Second, it reduces the tube's susceptibility to internal cracking which prolongs its fatigue life. Unfortunately, autofrettage also bears an inherent detrimental effect as it considerably increases the tensile hoop stress at the outer portion of the barrel's wall, which enhances external cracking of the tube by increasing the prevailing Stress Intensity Factor(SIF). In order to quantify this disadvantageous effect, 3-D Mode I SIFs distributions along the front of a single external radial semielliptical crack initiating from the outer surface of an autofrettaged modern gun barrel, overstrained by either the Swage or the Hydraulic autofrettage processes, are evaluated. The analysis is performed by the finite element(FE) method, using singular elements along the crack front. Innovative residual stress fields(RSFs), incorporating the Bauschinger effect for both types of autofrettage are applied to the barrel.Hill's [1] RSF is also applied to the tube for comparison reasons. All three RSFs are incorporated in the FE analysis, using equivalent temperature fields, Values for K_(IA)-the SIF resulting from the tensile residual stresses induced by autofrettage are evaluated for: a typical barrel of radii ratio R_o/R_i = 2, crack depth to wall-thickness ratios(a/t = 0.005-0.1),crack ellipticities(a/c = 0.2-1.0),and five levels of Swage,Hydraulic and Hill's autofrettage(e = 40%,60%,70%,80%,and 100%). In total,375 different 3-D cases are analyzed. The analysis demonstrates undoubtedly the detrimental effect of all types of autofrettage in increasing the prevailing effective stress intensity factor of external cracks, resulting in crack initiation enhancement and crack growth rate acceleration which considerably shortens the total fatigue life of the barrel. Nonetheless, the detrimental effect is autofrettage-type dependent. Swage and Hydraulic autofrettage RSFs differ substantially from each other. The disadvantageous effect of Swage autofrettage is much greater than that resulting from Hydraulic autofrettage. The results also emphasize the significance of the Bauschinger effect and the importance of the 3-D analysis.展开更多
To investigate the formation of fouling in sewage heat exchangers, a model of thermal resistance with time is developed based on the experiments in a practical engineering site. And this model is asymptotic exponentia...To investigate the formation of fouling in sewage heat exchangers, a model of thermal resistance with time is developed based on the experiments in a practical engineering site. And this model is asymptotic exponential function. According to the characteristic of sewage heat exchangers, the effective thermal resistance and effective coefficient of heat transmission during the formation of fouling are defined. A model for pressure loss of fouling of asymptotic distribution is presented based on the model of thermal resistance of fouling. And the maximum absolute margin of error of the fouling thermal resistance is smaller than the typical allowable error range. The maximum relative error of the heat transfer coefficient is 12%. These can meet the requirements of engineering. The resuhs of experiments provide a basis for further study and application of swage heat exchangers.展开更多
Effects of hydraulic retention time (HRT ) and gas volume on efficiency of wastewater treatment are dis- cussed based on a simulation experiment in which the domestic swage was treated by the two-stage-bio-contact oxi...Effects of hydraulic retention time (HRT ) and gas volume on efficiency of wastewater treatment are dis- cussed based on a simulation experiment in which the domestic swage was treated by the two-stage-bio-contact oxida- tion process. The result shows that the average CODCr, BOD5 , suspended solid (SS), and ammonia-nitrogen removal rate are 94.5 %, 93.2 %, 91.7 % and 46.9 %, respectively, under the conditions of a total air/water ratio of 5∶1 , an air/water ratio of 3:1 for oxidation tank 1 and 2:1for oxidation tank 2and a hydraulic retention time of 1 h for each stage. This method is suitable for domestic sewage treatment of residential community and small towns as well.展开更多
Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repai...Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repaired with the spinning reshaping technology;if the repairingforce or torque is too large, it will result in the damage of casing and cement sheath as well as sticking accident. So, the collapse experimentswere performed on the YAW-200 pressure testing machine by using one production casing which is often used in the oilfield and then thereshaping test of deformed casing (C110) was performed in turn by using two spinning casing swages of which the diameter is 126 mm and129 mm respectively. The continuous rotator and thrust bearing were used to provide the torque and reshaping force respectively in the repairingprocess. The reshaping force and torque required to reshape the deformed casing, the deformation law and the springback value of deformedcasing were obtained. Test results show that the diameter differential between the two spinning casing swages is reasonable. Furthermore, inorder to ensure the safety and reliability of the implementation of post-production technologies, the mechanical properties of deformed casingbefore and after reshaping were tested. It was found that all the mechanical parameters of the deformed casing after reshaping reduced, whichresulted in the decrease of the strength of the reshaped casing. These research achievements would provide important experimental data inoptimizing the structure and construction parameters of spinning casing swages.展开更多
The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materia...The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.展开更多
基金funded by the project SP2024/089 of the Specific Research of the VŠB-Technical University of Ostrava and realized within the framework of the Johannes Amos Comenius Program,Materials and Technologies for Sustainable Development-MATUR,No.CZ.02.01.01/00/22_008/0004631Brno University of Technology project No.FSI-S-23-8231“Investigation of Dynamic Deformation Behavior ofMetallicMaterials Prepared via Alternative Production Methods”.
文摘The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a temperature of 900℃.True flow stress-strain curves were determined for 600℃–900℃and used to construct a Hensel-Spittel model for FEM simulation.The process parameters,i.e.,stress,temperature,imposed strain,and force,were investigation during the rotary swaging process.Firstly,the stresses induced during rotary swaging and the resistance of the material to deformation were investigated.The amount and distribution of imposed strain in the cross-section can serve as a valuable indicator of the reduction in porosity and the texture evolution of the material.The simulation revealed the force required to swag the Dievar alloy.It also showed the evolution of temperature,which is important for phase transformation during solidification.Furthermore,microstructure evolutionwas observed before and then after rotary swaging.Dievar alloy is a critical material in the manufacture of dies for high-pressure die casting,forging tools,and other equipment subjected to high temperatures and mechanical loads.Understanding its viscoelastoplastic behavior under rotary swaging conditions is essential to optimize its performance in these demanding industrial applications.
基金Funding support of this work was carried out within the governmental task#075-00319-25-00.
文摘A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the formation of a recrystallized microstructure after RS with a grain size of 3.2±0.2μm leads to an increase in the strength of the alloy without reduction of level of ductility and corrosion resistance.At the same time,aging of the quenched alloy at 100℃ for 8 h leads to a slight increase in strength,but significantly reduces its ductility and corrosion resistance.The study of the degradation process of the alloy in the quenched state and after RS,both under in vitro and in vivo conditions,did not reveal a significant difference between these two microstructural states.However,an increase in the duration of incubation of the alloy in a complete growth medium from 4 h to 24 days leads to a decrease in the degradation rate(DR)by 4times(from~2 to~0.5 mm/year)due to the formation of a dense layer of degradation products.The study of biocompatibility in vitro did not reveal a significant effect of RS on the hemolytic and cytotoxic activity of the alloy.No signs of systemic toxicity were observed after subcutaneous implantation of alloy samples into mice before and after RS.However,it was found that RS promotes uniform degradation of the alloy over the entire contact surface.In summary,RS at 350℃ allows to increase the strength of Mg-1%Zn-0.6%Ca alloy up to348±5 MPa at a ductility level of 17.3±2.8%and a DRin vivoequal to 0.56±0.12 mm/year without impairing its biocompatibility in vitro and in vivo.
基金Project (U0834002) supported by the Key Program of NSFC Guangdong Joint Funds of ChinaProjects (51005079, 20976055) supported by the National Natural Science Foundation of China+1 种基金Project (10451064101005146) supported by the Natural Science Foundation of Guangdong Province, ChinaProject (20100172120001) supported by Specialized Research Fund for the Doctoral Program of Higher Education, China
文摘A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.
基金Xin Chen,Chuming Liu,Yingchun Wan and Zhiyong Chen acknowledge National Natural Science Foundation of China(Grant number 51574291 and 51874367).
文摘A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compression yield asymmetry,compared with that prepared via room-temperature rotary swaging.Transmission electron microscopy investigations showed that at the initial stage,multiple twins,mostly tension twins,were activated and intersected with each other,thereby refining the coarse grains into a fine lamellar structure.Then,two types of nanoscale subgrains were generated with increasing swaging strain.The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries.This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress.The second type of nanoscale subgrain was formed within the twin lamellae.The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays.Finally,randomly oriented nanograins were obtained via dynamic recrystallization,under the combined function of deformation heat and increased stored energy.Compared with room-temperature rotary swaging,cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.
文摘Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.
基金Funding support of investigations of microstructure,mechanical properties,corrosion resistance,biocompatibility and cytotoxicity was provided by the Russian Science Foundation(project#18-45-06010)Part of this work relating to studies of fatigue behavior was carried out within the governmental task#075-00947-20-00.
文摘Rotary swaging(RS)of alloy Mg-1.03Zn-0.66Ca(ZX11)was shown to refine the average grain size to 4.5±1.2μm in a longitudinal section and 4.8±0.9μm in a transverse section.In addition,a small amount of Mg2Ca particles about 300nm in size and Mg6Zn3Ca2 particles with a size of about lOOnm was detected.This resulted in pronounced strengthening:the yield strength and the ultimate tensile strength rose to 210±8 MPa and 276±6 MPa,respectively,while the elongation hardly decreased(22.0±1.8% and 18.3±2.9% before and after RS).Furthermore,RS led to an increase in the fatigue limit of the alloy from 120 MPa to 135 MPa and did not impair its resistance to chemical corrosion.The studies in vitro showed that ZX11 induces hemolysis without inhibiting the viability of peripheral blood mononuclear cells and has a more pronounced cytotoxic effect on tumor cells in comparison with non-transformed cells.No significant difference of the latter effect between the initial and the deformed states was observed.
基金financially supported by the National Natural Science Foundation of China(Nos.51471031 and U1660115)the State Key Laboratory for Advanced Metals and Materials(No.2016Z-17)。
文摘Tensile behavior of an equiaxed-grained Fe-6.5 wt.%Si alloy,which was deformed intoφ6 mm bar by hot rotary swaging,was investigated at various temperatures(300–400℃)and stretching rates(0.42–1 mm/min).The results revealed an enhancement in the intermediate-temperature tensile ductility after heat treatments.Deformation twinning was found in the equiaxed-grained Fe-6.5 wt.%Si bars during the tensile test,and heat treatments can enhance the deformation twinning.More twins can be observed in the necking areas than other regions.The high Schmid factor values above 0.4 after heat treatments demonstrated that deformation twinning can easily occur in the equiaxed-grained Fe-6.5 wt.%Si alloy.Higher deformation temperatures,higher strain rates,and larger degree of order suppressed the formation of deformation twinning,while the grain sizes had little effect on the deformation twinning.The twinning stress of the Fe-6.5 wt.%Si alloy increased with the increasing grain size,which did not agree with the Hall–Petch type relationship.The deformation twinning resulted in the improved ductility of the Fe-6.5 wt.%Si alloy.
基金National Natural Science Foundation of China(No.51175413)
文摘In this paper,an elasto-viscoplastic three-dimension(3D) finite element model is developed to simulate the processing of bimetal tube with rotary swaging. Through simulation,the effects of high-frequency pulse stroking on the distribution and histories of stress,stain and loading are clarified. The stress in inner tube is compressive and higher than the minimum bonding force. Meanwhile,the stiffness of inner tube impacts outer tube extension in length.
文摘This paper presents the parametric analysis conducted to derive the optimal dimensions of the steel sleeve necessary to secure the bond performance of the swaging type anchorage for CFRP tendon with diameter of 5 mm. To that goal, finite element analysis is performed on the parameters determining the dimensions of the sleeve like the thickness and inner diameters of the sleeve. The results show that a constant swaging pressure of about 450 MPa on the mean is distributed in the sleeve when the thickness ratio of the stress relief zone to the effective swaging zone of the sleeve is larger than 1.1 and that the swaging pressure tends to reduce linearly as much as this thickness ratio becomes smaller than 1.1. The pressure varies within a range of about 30% according to the change in the inner diameter of the sleeve whereas varies within a range less than 10% according to the change in the inner diameter when the thickness ratio is larger than 1.1. Finally, the optimal dimensions of the steel tube sleeve enabling to secure an anchor force larger than the rupture strength of the CFRP tendon with diameter of 5 mm are determined based upon the results of the parametric analysis.
基金supported by the National Natural Science Foundation of China(grant no.U21A2079)the China Post-doctoral Science Foundation(grant no.2024M753342)+3 种基金the Post-doctoral Fellowship Program of CPSF(grant no.GZB20230786)the Ningbo International Cooperation Project(grant no.2023H002)the Ningbo Science&Technology Project(grant no.2023A-160-B)the Ningbo Science&Technology Innovation 2025 Major Project(grant no.2022Z187).
文摘The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7)Se_(0.3) material with a certain textured structure is prepared by an innovative rotary swag-ing method.It is found that various defects including Te vacancies,dislocations,and grain boundaries significantly strengthen the phonon scattering.With an obviously suppressed thermal conductivity and well-maintained carrier mobility,the obtained rods extending up to several tens of centimeters achieve a peak ZT of 1.2 at 450 K and an average ZT of 1.0(300-550 K),with Vickers hardness and compressive strength increased to 0.42 GPa and 52.6 MPa,respectively.Moreover,the assembled 17-pair thermoelec-tric module achieves a competitive conversion efficiency of up to 6.3% and a high output power of 0.93 W at a temperature difference of 250 K.This study develops an effective strategy for synergistically en-hancing the thermoelectric and mechanical properties of n-type Bi_(2)(Te,Se)_(3).
基金financial supports from National Key R&D Program of China(No.2021YFA1200203)National Natural Science Foundation of China(Nos.51971112,51225102,and 52171119)+3 种基金Jiangsu Province Leading Edge Technology Basic Research Major Project(No.BK20222014)Fundamental Research Funds for the Central Universities(No.2023201001)Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2023ZB091)China Postdoctoral Science Foundation(No.2023M741699)。
文摘Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employing rotary swaging(RS),bulk NC Cu–15 at.%Al alloys with both high strength and high thermal stability were prepared.Quasi-static tensile test results show that the yield strength is 1016 MPa.Moreover,the grain growth temperature was retarded up to 0.4 Tm,higher than the literature values.Microstructural characterizations revealed that after RS deformation,coarse-grained Cu–Al was refined into fibrous NC grains with a diameter of 45 nm and a length of 190 nm,and the contents of high-angle grain boundaries(GBs),low-angle GBs,and twin boundaries are 17%,45%,and 38%,respectively.Moreover,there is a significant multiscale chemical fluctuation within the grains,at the GBs,and between the grains through extreme defect accumulation.The atomistic simulation suggests that the segregation behavior of Al solute is essentially driven by the atomic size and local stress state.Besides,Al segregation greatly reduces the grain boundary energy,which further improves the thermal stability of the material.The main strengthening mechanism is Hall–Petch strengthening and the strengthening brought by the chemical fluctuations.Our work provides ideas for designing strong and thermally stable bulk NC alloys.
基金financially supported by the International Thermonuclear Experimental Reactor(ITER) Project of China(No.2014GB123000)
文摘Pure tungsten （PW） and W-1 wt% La203 （WL10） were prepared by powder metallurgical route fol- lowed by the swaging ＋ rolling process. The logarithmic strains are 0, 0.37, 0.58, and 0.98 for WL10 and 0, 0.58 for PW. Heat treatments were performed at temperatures var- ied from 1,573 to 2,173 K to determine the recrystalliza- tion temperature. Recrystallization temperatures are 1,973 and 2,173 K for WL1 （logarithmic strain of 0.37） and WL3 （logarithmic strain of 0.98）, respectively. But in the case of WL2 （logarithmic strain of 0.58）, full recrystallization is not achieved at temperature of above 2,173 K. Further- more, the recrystallization temperature of PW with loga- rithmic strain of 0.58 is at least 300 K lower than that of the equivalent WLI0 sample. Moreover, the increase of recrystallization temperature inhibits the strength degra- dation of WL2： samples lose 4 % and 22 % strength when annealed at 1,573 and 1,973 K compared with room tem- perature （RT） sample. Finally, the texture evolution for the swaged ＋ rolled WL10 is significantly related to the deformation degree： the dominated orientation is （001） for WL2 while （110） for WL3.
基金Project(2014CB644002)supported by the National Key Fundamental Research and Development Project of ChinaProject(51301203)supported by the National Natural Science Foundation of China+1 种基金Project(2015CX004)supported by the Innovation-driven Plan in Central South University,Chinasupported by the Outstanding Graduate Project of Advanced Non-ferrous Metal Structural Materials and Manufacturing Collaborative Innovation Center,China
文摘The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on microstructures and mechanical properties were investigated using the SEM, TEM, OM and the universal material testing machine. Results show that the alloy can be easily hot forged and cold swaged due to the fine-grained microstructure. Only after cold swaging by 85%, the alloy shows the typical ＂marble-like＂ structure. And thecold deformation is accompanied by stress-induced a＂ phase transformations. Moreover, both the strength and the ductility of the alloy are significantly improved by hot and cold working.
基金support by the Egyptian Science and Technology Development Fund (STDF)the German International Bureau of the Federal Ministry of EducationResearch under project number EGY 08-070 is gratefully acknowledged
文摘The influence of hot swaging（SW） and annealing treatment on microstructure and mechanical properties of commercially pure titanium produced by investment casting was evaluated.The as-cast samples showed a typical microstructure consisting of a variety of α-morphologies,while the hot swaged samples exhibited a kinked lamellar microstructure.Annealing at 500 °C did not significantly change this microstructure while annealing at 700 and 870 °C led to recrystallization and formation of equiaxed microstructures.The cast bars exhibited a typical hard α-layer in near-surface regions with a maximum depth and maximum hardness of 720 μm and HV0.5 660,respectively.Due to SW,the tensile strength of the as-cast material drastically increased from 605 MPa to 895 MPa.Annealing at 500 °C decreased the tensile strength slightly from 895 to 865 MPa while annealing at 700 °C led to a further pronounced drop in tensile strength from 865 to 710 MPa.No additional decrease in tensile strength was noticed with increasing the annealing temperature from 700 to 870 °C.The true fracture strain of the as-cast and hot swaged samples was in the range of 0.05 to 0.12,while the annealed samples showed values in the range of 0.25 to 0.53.In addition,the as-cast and hot swaged samples revealed a brittle cleavage fracture surfaces.However,the annealed samples showed a transgranular ductile fracture with formation of dimples.
文摘Overstraining gun tubes has a twofold advantage. First, it enables the increase of the Safe Maximum Pressure(SMP) in the tube, resulting in a higher muzzle velocity which extends the gun's range and its projectile kinetic energy. Second, it reduces the tube's susceptibility to internal cracking which prolongs its fatigue life. Unfortunately, autofrettage also bears an inherent detrimental effect as it considerably increases the tensile hoop stress at the outer portion of the barrel's wall, which enhances external cracking of the tube by increasing the prevailing Stress Intensity Factor(SIF). In order to quantify this disadvantageous effect, 3-D Mode I SIFs distributions along the front of a single external radial semielliptical crack initiating from the outer surface of an autofrettaged modern gun barrel, overstrained by either the Swage or the Hydraulic autofrettage processes, are evaluated. The analysis is performed by the finite element(FE) method, using singular elements along the crack front. Innovative residual stress fields(RSFs), incorporating the Bauschinger effect for both types of autofrettage are applied to the barrel.Hill's [1] RSF is also applied to the tube for comparison reasons. All three RSFs are incorporated in the FE analysis, using equivalent temperature fields, Values for K_(IA)-the SIF resulting from the tensile residual stresses induced by autofrettage are evaluated for: a typical barrel of radii ratio R_o/R_i = 2, crack depth to wall-thickness ratios(a/t = 0.005-0.1),crack ellipticities(a/c = 0.2-1.0),and five levels of Swage,Hydraulic and Hill's autofrettage(e = 40%,60%,70%,80%,and 100%). In total,375 different 3-D cases are analyzed. The analysis demonstrates undoubtedly the detrimental effect of all types of autofrettage in increasing the prevailing effective stress intensity factor of external cracks, resulting in crack initiation enhancement and crack growth rate acceleration which considerably shortens the total fatigue life of the barrel. Nonetheless, the detrimental effect is autofrettage-type dependent. Swage and Hydraulic autofrettage RSFs differ substantially from each other. The disadvantageous effect of Swage autofrettage is much greater than that resulting from Hydraulic autofrettage. The results also emphasize the significance of the Bauschinger effect and the importance of the 3-D analysis.
基金Sponsored by the National Natural Science Foundation of China(Grant No. 50578048)
文摘To investigate the formation of fouling in sewage heat exchangers, a model of thermal resistance with time is developed based on the experiments in a practical engineering site. And this model is asymptotic exponential function. According to the characteristic of sewage heat exchangers, the effective thermal resistance and effective coefficient of heat transmission during the formation of fouling are defined. A model for pressure loss of fouling of asymptotic distribution is presented based on the model of thermal resistance of fouling. And the maximum absolute margin of error of the fouling thermal resistance is smaller than the typical allowable error range. The maximum relative error of the heat transfer coefficient is 12%. These can meet the requirements of engineering. The resuhs of experiments provide a basis for further study and application of swage heat exchangers.
文摘Effects of hydraulic retention time (HRT ) and gas volume on efficiency of wastewater treatment are dis- cussed based on a simulation experiment in which the domestic swage was treated by the two-stage-bio-contact oxida- tion process. The result shows that the average CODCr, BOD5 , suspended solid (SS), and ammonia-nitrogen removal rate are 94.5 %, 93.2 %, 91.7 % and 46.9 %, respectively, under the conditions of a total air/water ratio of 5∶1 , an air/water ratio of 3:1 for oxidation tank 1 and 2:1for oxidation tank 2and a hydraulic retention time of 1 h for each stage. This method is suitable for domestic sewage treatment of residential community and small towns as well.
文摘Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repaired with the spinning reshaping technology;if the repairingforce or torque is too large, it will result in the damage of casing and cement sheath as well as sticking accident. So, the collapse experimentswere performed on the YAW-200 pressure testing machine by using one production casing which is often used in the oilfield and then thereshaping test of deformed casing (C110) was performed in turn by using two spinning casing swages of which the diameter is 126 mm and129 mm respectively. The continuous rotator and thrust bearing were used to provide the torque and reshaping force respectively in the repairingprocess. The reshaping force and torque required to reshape the deformed casing, the deformation law and the springback value of deformedcasing were obtained. Test results show that the diameter differential between the two spinning casing swages is reasonable. Furthermore, inorder to ensure the safety and reliability of the implementation of post-production technologies, the mechanical properties of deformed casingbefore and after reshaping were tested. It was found that all the mechanical parameters of the deformed casing after reshaping reduced, whichresulted in the decrease of the strength of the reshaped casing. These research achievements would provide important experimental data inoptimizing the structure and construction parameters of spinning casing swages.
基金supported by the National Natural Science Foundation of China(Nos.52371093 and 52171104)the National Key Research and Development Program of China(No.2021YFB3701100)the Chongqing Research Program of Basic Research and Frontier Technology,China(Nos.CSTB2023NSCQ-BSX0036 and cstc2021ycjh-bgzxm0086).
文摘The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.
