中文摘要：

通过OM、SEM、XRD、TEM及力学性能测试等手段,研究了热处理工艺及挤压对WE91镁合金的显微组织及力学性能的影响。结果表明,铸态WE91合金主要由α-Mg基体及共晶组织构成。经过均匀化处理后,合金中大量的共晶组织回溶,主要的未溶相为Mg12（MM）;经过挤压后,合金发生动态再结晶,晶粒尺寸明显减小,均匀化后残留的Mg12（MM）相沿挤压方向呈流线分布;WE91合金合理的时效热处理制度为225℃×28h,此时析出大量的长透镜片状β相;时效后合金具有较高的耐高温性能,250℃以下,合金的强度下降有限,达到300℃时,合金的强度显著下降。随着测试温度提高,合金裂纹萌生从晶内逐渐转移至晶界。

英文摘要：

Effect of heat treatment process and extrusion on microstructure and properties of WE91 alloy were investigated by means of optical microscopy,scanning electron microscopy,X-ray diffraction,transmission electron microscopy and mechanical property tests.The results reveal that the as-cast WE91 alloy is composed mainly ofα-Mg matrix and eutectic structures of Mg24Y5 and Mg12（MM）phases.After homogenization treatment,most of eutectic structures in the alloy are dissolved fully besides the Mg12（MM）phase.After extrusion treatment,the alloy undergoes dynamic recrystallization,so the grain size of the alloy is decreased significantly.The residual Mg12（MM）phase is distributed along extrusion direction.With treating at 225 ℃ for 28 h,numerous long lens-shapedβ′phases are precipitated.After aging treatment,the alloy exhibits good resistance at high temperatures.The strength of the alloy is reduced slightly below 250℃,however,strength of the alloy is reduced significantly at 300℃.As the testing temperature increase,the crack propagation is changed from transgranular to intergranular.