Research On Deformation Mechanism Of WE43-T4 Rare Earth Magnesium Alloy Under Uniaxial Compression At Room Temperature

WE43(Mg-4.24Y-2.40Nd-1.03Gd-0.56Zr)rare earth magnesium alloy has many advantages,such as good high strength,heat resistance,creep resistance,biocompatibility,flame retardancy,etc.,and has great development potential in the fields of national defense,security,aerospace and other fields.Uniaxial compression test is an effective way to obtain the data of the mechanical properties of metal materials,the influence of the deformation temperature,the deformation rate and the deformation degree on the internal deformation mechanism of the metal material can be determined.The heat treatment state can affect the uniaxial compressive plastic deformation of WE43 magnesium alloy.At present,there are many researches have been focused on the uniaxial compression of aged(T5)and aged + solid solution(T6)WE43 alloys at elevated temperature,but few on the uniaxial compression of solid solution treated(T4)WE43 alloys at room temperature.Consequently,the present study aims to tackle the aforementioned issue.In this paper,WE43 rare earth magnesium alloy after solution treatment(WE43-T4)is used as the experimental material.Uniaxial compression,Optical microstructure(OM),X-ray diffractometer(XRD)and electron backscattered diffraction(EBSD)characterizations are used to study the influence of loading direction and grain size on the mechanical properties,and microstructure evolution characteristics related to the involved deformation mechanism such as dislocation slip and deformation twinning of WE43-T4 Mg alloy is investigated.Based on this,Schmid factor(SF)of various deformation mechanisms is also systemically calculated.The main conclusions of this paper are as follows:1.All samples(0° sample,45°sample and 90°sample)exhibit minor plastic anisotropy during uniaxial compression at room temperature.However,due to the difference in the initial loading direction of each sample,the deformation mechanism of activated basal <a> slip,prismatic <a> slip,{10(?)2} extension twins(ET)and {1(?)21} ET are different during the deformation process,thus showing slight differences in macro yield strength and strain hardening rate between samples.The difference of 0.2% proof yield strength is closely related to the prismatic <a> slip,{10(?)2} ET and{1(?)21} ET,and the different decreasing strain hardening rates are closely related to the SF value of basal <a> slip.By increasing the angle of compression direction(CD)and extrusion direction(ED),the volume fraction of {10(?)2} ET and {1(?)21} ET boundary decrease.These two types of ET are responsible for the formation of texture at the early stage of deformation,while the formation of tilted basal texture at the later stage of deformation is mainly related to the pyramidal <c+a> slip and the activation of {10(?)1}-{10(?)2} double twins(DT).2.The increase in grain size is beneficial to the nucleation and growth of {10(?)2} ET,and will reduce the number of activated {10(?)2} ET variants in the single grain which only contains {10(?)2}ETs.These activated {10(?)2} ETs can cause a rapid concentration towards compression direction(CD)of the c-axis of grains,forming a basal texture component.This issue will reduce its plastic deformation ability.However,the decrease in grain size will lead to an increase of the relative fraction of grain boundaries(GBs),so the dislocation motion is limited and the yield strength is then increased.The increase in grain size is also beneficial to the nucleation and growth of {1(?)21} ETs,but the number of its variants is not affected by the grain size.A large number of pyramidal <c+a> slip and{10(?)1}-{10(?)2} DTs are activated within these samples at the later stage of plastic deformation,which results in the non-basal texture with their c-axis deviating about 30° from CD.