Influence Of Grain Size And Orientation On Mechanical Properties Of Mg-10Gd-2Y-0.5Zr(wt.%) Alloy

High property magnesium alloys containing yttrium or rare earth elements are attractive as light structural materials for the aerospace and automotive industries.It has been reported that the recently developed Mg-Gd-Y alloys exhibit higher specific strength at both room and elevated temperatures than conventional Al and Mg alloys,including WE54,whose high temperature strength is the top of existing commercial magnesium alloys.In this paper Mg-10Gd-2Y-0.5Zr(wt.%)alloy,which exhibits excellent mechanical properties,was researched.On one hand,after solution treatment(500℃),solution and aging treatment(250℃),the mechanical properties were tested in three orientations(0°,45°,90°)tilting the extrusion direction,in order to investigate the mechanical property anisotropy of the alloy.The results show that after solution and aging treatment,the samples obtained excellent mechanical properties:in the 0°direction the average tensile yield strength was 434±14.8MPa MPa with the 7%elongation percentage;mechanical twinning and tension-compression yield asymmetry were not found in both solution treatment samples and solution plus aging treatment samples,besides Y,the reduction of c/a,Grain boundary slipping(GBS)limits the occurrence of twinning;for the difference of orientation factors,mechanical property anisotropy was obvious:in the 0°direction the yield strength was highest,the yield strength was similar in the 45°and 90°directions,in the 45°direction elongation percentage was highest.On the other hand,a combined of Equal Channel Angular Pressing and Forward Extrusion method was employed to prepare samples with different textures.Then annealing(500℃)was introduced to the ECAP 4-Pass and 4P+Extrusion samples respectively to get the samples with different grain sizes.The relations of mechanical property and grain size in each texture was gained and investigated.The results show that the yield strength and grain size in both solid solution(SS)+ECAP+Anneal samples and SS+ECAP+Anneal+Aging samples do not obey the Hall-Petch relation,and the tensile yield strength and grain size obey the Hall-Petch relation,σ_0.2= 95 + 346d ^(-1)/2.Besides grain size,the evolution of texture after heat treatment has important effects on the mechanical property.