退火处理对预变形Mg-5.3Nd合金压缩强度的影响

Annealing treatment on compress strength of pre-deformed Mg-5.3Nd alloy

摘要:

通过光学显微镜、XRD、SEM/EDS以及常温压缩试验等方法对Mg-5.3Nd合金的金相组织、退火强化行为以及压缩变形机制等进行了研究，结果表明：550 ℃×8 h固溶处理后，铸态Mg-5.3Nd合金的第二相Mg12Nd基本消除。经预压缩-卸载-再压缩试验，固溶Mg-5.3Nd合金的压缩强度没有明显变化，而预压缩-卸载-退火处理-再压缩试验后，合金的压缩强度明显提高，并获得最佳强化效果的退火工艺为180 ℃×4 h。原位金相分析发现，未退火试样的再压缩变形机制表现为预变形孪晶的明显长大。而预变形试样退火后，由于钕元素对预变形孪晶的钉扎作用，其再压缩变形机制以新变形孪晶的形成为主。

Abstract:

The microstructure, annealing strengthen and compressive deformation mechanism of Mg-5.3Nd alloy were investigated by using of OM, XRD, SEM/EDS and room temperature compression test, the results showed that the main second phase on as-casting Mg-5.3Nd alloy was Mg12Nd and the optimal solution treatment was 550 ℃×8 h for eliminating the second phases. Not subsequent unload and recompression but annealling treatment between pre-compression and recompression could markedly increase the compression strength of pre-deformed Mg-5.3Nd solid solution and the optimal annealing process was 180℃×4 h to reach the strength increament of 47MPa. The in-situ optical micrographs indicated that the preformed twins in the pre-compressed Mg-5.3Nd alloy untreated by annealing obviously grew up during the subsequent compression, whereas after annealing treatment the second compression deformation proceeded by the initiation of the new twins rather than the growth of the prefromed ones for the diffusion segregation of Nd element in the twin grainboudary during annealing process.