The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensi...The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.展开更多
Increasing the plastic deformation temperature of Mg alloys results in higher strain rate sensitivity,easier activation of secondary slip modes,and impeded twinning.In this study,the strain rate sensitivity is estimat...Increasing the plastic deformation temperature of Mg alloys results in higher strain rate sensitivity,easier activation of secondary slip modes,and impeded twinning.In this study,the strain rate sensitivity is estimated for each deformation mode,and visco-plastic self-consistent modeling is used to reproduce the plastic deformation behavior of an Mg-3Al-lZn O-temper plate from 150 to 450℃.Twinning and basal slip have relatively low strain rate sensitivity,whereas secondary slip modes are highly strain rate sensitive at high temperature.The texture evolution and plastic anisotropy are modeled at different temperatures and strain rates.Results show that when the strain rate sensitivity is taken into account,compared with rate independent critical resolved shear stresses,the material parameters and predictions are different.In particular,this study shows that,for hot deformation,there is a critical strain rate above which secondary slip modes predominate,and beyond which tension twinning is activated.A similar transition is expected for modes that have different strain rate sensitivity.展开更多
The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly ...The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction(EBSD) measurement and visco-plastic self-consistent(VPSC) modeling. These results show that except basal slip and prismatic slip, {10■2} extension twin(ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction(RD) of sheet, the activity of {10■2} ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When {10■2} ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component(c-axis//ND, normal direction). By comparison, when the role of {10■2} ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component(c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal<c+a> slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal <c+a> slip, the smaller separation is between these two tilted basal poles. Besides,VPSC modeling overesttmates volume fractions of {10■2} ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of {10■2} ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.展开更多
The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work,the tensile mechanical property test and visco-plastic s...The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work,the tensile mechanical property test and visco-plastic self-consistent (VPSC) model are used to investigate the activities of deformation modes of VW84M and VW94M magnesium alloys during the tensile deformation. The results show that the mechanical properties of the above extruded alloys are similar but VW94M has higher strength than VW84M after the same aging process. Compared with the extruded alloys,the as-aged alloys have significantly higher activation of pyramidal slip at the later stage of plastic deformation. In addition,the as-aged VW94M alloy with higher strength has the largest activity of pyramidal slip. In summary,the addition of Gd increases the critical resolved shear stress (CRSS)in each slip system of VW94M,while the increase in the strength and the decrease in the elongation of as-aged alloys are associated with the significant activation of pyramidal slip.展开更多
基金The authors thank the National Key R&D Program of China(2016YFB0301100)National Natural Science Foundation of China(51571043)+1 种基金Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYB18004)Fundamental Research Funds for the Central Universities(Nos.2018CDJDCL0019,cqu2018CDHB1A08 and 2018CDGFCL0005).
文摘The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.
基金Thanks go to C.Tome for sharing the VPSC code.This study was supported by the National Natural Science Foundation of China(51421001)the'111' Project(B16007)by the Ministry of Education.
文摘Increasing the plastic deformation temperature of Mg alloys results in higher strain rate sensitivity,easier activation of secondary slip modes,and impeded twinning.In this study,the strain rate sensitivity is estimated for each deformation mode,and visco-plastic self-consistent modeling is used to reproduce the plastic deformation behavior of an Mg-3Al-lZn O-temper plate from 150 to 450℃.Twinning and basal slip have relatively low strain rate sensitivity,whereas secondary slip modes are highly strain rate sensitive at high temperature.The texture evolution and plastic anisotropy are modeled at different temperatures and strain rates.Results show that when the strain rate sensitivity is taken into account,compared with rate independent critical resolved shear stresses,the material parameters and predictions are different.In particular,this study shows that,for hot deformation,there is a critical strain rate above which secondary slip modes predominate,and beyond which tension twinning is activated.A similar transition is expected for modes that have different strain rate sensitivity.
基金the National Natural Science Foundation of China(Grant Nos.51805064,51701034,51822509)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant Nos.KJQN201801137)the Basic and Advanced Research Project of CQ CSTC(Grant Nos.cstc2017jcyj AX0062,cstc2018jcyj AX0035)。
文摘The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction(EBSD) measurement and visco-plastic self-consistent(VPSC) modeling. These results show that except basal slip and prismatic slip, {10■2} extension twin(ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction(RD) of sheet, the activity of {10■2} ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When {10■2} ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component(c-axis//ND, normal direction). By comparison, when the role of {10■2} ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component(c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal<c+a> slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal <c+a> slip, the smaller separation is between these two tilted basal poles. Besides,VPSC modeling overesttmates volume fractions of {10■2} ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of {10■2} ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.
文摘The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work,the tensile mechanical property test and visco-plastic self-consistent (VPSC) model are used to investigate the activities of deformation modes of VW84M and VW94M magnesium alloys during the tensile deformation. The results show that the mechanical properties of the above extruded alloys are similar but VW94M has higher strength than VW84M after the same aging process. Compared with the extruded alloys,the as-aged alloys have significantly higher activation of pyramidal slip at the later stage of plastic deformation. In addition,the as-aged VW94M alloy with higher strength has the largest activity of pyramidal slip. In summary,the addition of Gd increases the critical resolved shear stress (CRSS)in each slip system of VW94M,while the increase in the strength and the decrease in the elongation of as-aged alloys are associated with the significant activation of pyramidal slip.
