The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rat...The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.展开更多
The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate r...The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate range of 0.01-10 s -1 ,the corresponding flow curves and their characters were determined and analyzed,and microstructures were studied by optical,SEM and TEM microscopy.The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15,coarsening of the precipitated phase and dynamic recrystallization（DRX）of the phase of matrix,leading to the formation of the polyphase（η＋ε＋TiZn15）structure.The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix.The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature,and the degree of DRX became more complete when the strain rate and strain became larger.Hot deformation accelerated the diffusion of Cu atom,which resulted in the coarsening of the precipitated phase.Thus,the microstructure was refined owing to the pinning effect of the precipitated phase.展开更多
The diffusion-multiple method was used to determine the composition of Ti−6Al−4V−xMo−yZr alloy(0.45<x<12,0.5<y<14,wt.%),which can obtain an ultrafine α phase.Results show that Ti−6Al−4V−5Mo−7Zr alloy can ...The diffusion-multiple method was used to determine the composition of Ti−6Al−4V−xMo−yZr alloy(0.45<x<12,0.5<y<14,wt.%),which can obtain an ultrafine α phase.Results show that Ti−6Al−4V−5Mo−7Zr alloy can obtain an ultrafineαphase by using the α″phase assisted nucleation.The bimodal microstructure obtained with the heat-treatment process can confer the alloy with a good balance between the strength and plasticity.The deformation mechanism is the dislocation slip and the{1101}twinning in the primary α phase.The strengthening mechanism is α/β interface strengthening.The interface of(0001)α/(110)β has a platform−step structure,whereas(1120)α/(111)βinterface is flat with no steps.展开更多
The flow stress behavior of Cu13Zn alloy was investigated by compression tests carried out at 650 ℃, 700 ℃, 750 ℃, 850 ℃, and constant strain rates of 0.05 s -1 , 0.1 s -1 , 0.5 s -1 , 1 s -1 , 5 s -1 , respective...The flow stress behavior of Cu13Zn alloy was investigated by compression tests carried out at 650 ℃, 700 ℃, 750 ℃, 850 ℃, and constant strain rates of 0.05 s -1 , 0.1 s -1 , 0.5 s -1 , 1 s -1 , 5 s -1 , respectively. The results show that the flow stress increases with the increase of strain and reaches a steady state stress, and the saturated stress ( σ s) increases with the increase of the strain rate and the decrease of temperature. Flow stress curves of the alloy deformed at elevated temperatures can be simulated effectively by the model proposed by Zhou and Clode, and the flow stress is described as a function of strain, strain rate and temperature. Material constants values are: Q =270.43 kJ/mol, α =0.020 94, A =1.747×10 11 s -1 and n = 3.549 mm 2·N -1 , the deformation mechanisms of the alloy are self diffusion and dynamic recovery.展开更多
Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents.Traditionally,it is believed that both high strength and excellent ductility can reduce fretting wear damage.H...Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents.Traditionally,it is believed that both high strength and excellent ductility can reduce fretting wear damage.However,whether strength and ductility are contradictory or not and their appropriate matching strategy under the external applied normal stress(Fw)are still confusing problems.Here,by analyzing the subsurface-microstructure deformation mechanism of several samples containing variousαprecipitate features,for the first time,we design strategies to improve fretting damage resistance under different matching relation between Fw and the tensile strength of materials(Rm).It is found that when Fw is greater than Rm or Fw is nearly equivalent to Rm,the deformation mechanism mainly manifests as serious grain fragmentation ofβandαGB constituents.Homogeneous deformation in large areas only reduces damage to a limited extent.It is crucial to improve the strength to resist cracking and wear,but it is of little significance to improve the ductility.However,when Fw is far less than Rm,coordinated deformation ability reflected by ductility plays a more important role.The deformation mechanism mainly manifests as localized deformation ofβandαGB constituents(kinking induced by twinning and spheroidizing).A unique composite structure of nano-grained/lamellar layer and localized deformation transition layer reduces fretting damage by five times compared with a single nanograined layer.Only when the strength is great enough,improving the plasticity can reduce wear.This study can provide a principle for designing fretting damage resistant alloys.展开更多
High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of mi...High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.展开更多
基金supported by the National Key R&D Program of China(No.2021YFB3701100)the National Natural Science Foundation of China(No.52271091)the China Scholarship Council(No.202206050135)。
文摘The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.
基金Project(2009BAE71B03)supported by the National Key Technology Support Program of China During the 11th Five-year Plan Period
文摘The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate range of 0.01-10 s -1 ,the corresponding flow curves and their characters were determined and analyzed,and microstructures were studied by optical,SEM and TEM microscopy.The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15,coarsening of the precipitated phase and dynamic recrystallization（DRX）of the phase of matrix,leading to the formation of the polyphase（η＋ε＋TiZn15）structure.The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix.The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature,and the degree of DRX became more complete when the strain rate and strain became larger.Hot deformation accelerated the diffusion of Cu atom,which resulted in the coarsening of the precipitated phase.Thus,the microstructure was refined owing to the pinning effect of the precipitated phase.
基金Projects(2016YFB0701301,2018YFB0704100)supported by the National Key Technologies R&D Program of ChinaProjects(51901251,51671218,51501229)supported by the National Natural Science Foundation of ChinaProject(2020JJ5750)supported by the Natural Science Foundation of Hunan Province,China。
文摘The diffusion-multiple method was used to determine the composition of Ti−6Al−4V−xMo−yZr alloy(0.45<x<12,0.5<y<14,wt.%),which can obtain an ultrafine α phase.Results show that Ti−6Al−4V−5Mo−7Zr alloy can obtain an ultrafineαphase by using the α″phase assisted nucleation.The bimodal microstructure obtained with the heat-treatment process can confer the alloy with a good balance between the strength and plasticity.The deformation mechanism is the dislocation slip and the{1101}twinning in the primary α phase.The strengthening mechanism is α/β interface strengthening.The interface of(0001)α/(110)β has a platform−step structure,whereas(1120)α/(111)βinterface is flat with no steps.
文摘The flow stress behavior of Cu13Zn alloy was investigated by compression tests carried out at 650 ℃, 700 ℃, 750 ℃, 850 ℃, and constant strain rates of 0.05 s -1 , 0.1 s -1 , 0.5 s -1 , 1 s -1 , 5 s -1 , respectively. The results show that the flow stress increases with the increase of strain and reaches a steady state stress, and the saturated stress ( σ s) increases with the increase of the strain rate and the decrease of temperature. Flow stress curves of the alloy deformed at elevated temperatures can be simulated effectively by the model proposed by Zhou and Clode, and the flow stress is described as a function of strain, strain rate and temperature. Material constants values are: Q =270.43 kJ/mol, α =0.020 94, A =1.747×10 11 s -1 and n = 3.549 mm 2·N -1 , the deformation mechanisms of the alloy are self diffusion and dynamic recovery.
基金supported by the National Natural Science Foundation of China(No.52105211)the Research Fund of the State Key Laboratory of Solidification Processing of NPU,China(No.2023-TS-04)the Fundamental Research Funds for the Central Universities of China(No.3102019JC001).
文摘Fretting wear damage of high-strength titanium fasteners has caused a large number of disastrous accidents.Traditionally,it is believed that both high strength and excellent ductility can reduce fretting wear damage.However,whether strength and ductility are contradictory or not and their appropriate matching strategy under the external applied normal stress(Fw)are still confusing problems.Here,by analyzing the subsurface-microstructure deformation mechanism of several samples containing variousαprecipitate features,for the first time,we design strategies to improve fretting damage resistance under different matching relation between Fw and the tensile strength of materials(Rm).It is found that when Fw is greater than Rm or Fw is nearly equivalent to Rm,the deformation mechanism mainly manifests as serious grain fragmentation ofβandαGB constituents.Homogeneous deformation in large areas only reduces damage to a limited extent.It is crucial to improve the strength to resist cracking and wear,but it is of little significance to improve the ductility.However,when Fw is far less than Rm,coordinated deformation ability reflected by ductility plays a more important role.The deformation mechanism mainly manifests as localized deformation ofβandαGB constituents(kinking induced by twinning and spheroidizing).A unique composite structure of nano-grained/lamellar layer and localized deformation transition layer reduces fretting damage by five times compared with a single nanograined layer.Only when the strength is great enough,improving the plasticity can reduce wear.This study can provide a principle for designing fretting damage resistant alloys.
基金the project of National Key Laboratory for Precision Hot Processing of Metals,Harbin Institute of Technology(No.6142909190207)Shaanxi Key Laboratory of High-Performance Precision Forming Technology and Equipment(NSKL-HPFTE)(No.PETE-2019-KF01)。
文摘High-strength β titanium alloys represented by near β titanium alloy and metastable β titanium alloy are preferred materials for large-scale load-carrying structures.In order to achieve the precise regulation of microstructure in the deformation process, massive efforts have been made to study the flow behavior and microstructure evolution of βtitanium alloy in the hot deformation process. This paper reviews the flow behavior of high-strength titanium alloy,including the effects of initial microstructure, deformation process parameters, work hardening, and dynamic softening on flow stress. Furthermore, the effects of deformation process parameters on the apparent activation energy for deformation and strain rate sensitivity coefficient are analyzed. The discontinuous yield phenomenon is discussed,and the constitutive models of flow stress are summarized.Furthermore, some microstructural evolution models are reviewed. Finally, the development direction and difficulties of the flow behavior and constitutive model are pointed out.
