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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。
The effects of heat treatment and extrusion on the microstructure and mechanical properties of WE91 magnesium alloy were studied by means of OM, SEM, XRD, TEM and mechanical properties test. The results show that the as-cast WE91 alloy is mainly composed of α-Mg matrix and eutectic structure. After homogenization treatment, a large amount of eutectic microstructure was dissolved back into the alloy, and the main undissolved phase was Mg12 (MM). After extrusion, the alloy recrystallized dynamically and its grain size decreased obviously. After homogenization, Mg12 (MM) phase flow along the extrusion direction was streamline; WE91 alloy reasonable aging heat treatment system is 225 ℃ × 28h, then precipitated a large number of long lens flake β phase; aging after the alloy has a high temperature resistance, 250 ℃, the decrease of the strength of the alloy is limited. When the temperature reaches 300 ℃, the strength of the alloy decreases significantly. With the increase of the test temperature, the initiation of alloy crack gradually shifts from the intragranular to the grain boundary.