Al_4C_3对AZ91D镁合金铸态显微组织与性能的影响

Effect of Al_4C_3 on the As Cast Microstructure and Properties of AZ91D Magnesium Alloy

借助SEM、EDS、XRD、DTA研究Al4C3对AZ91D镁合金铸态显微组织与性能的影响。结果表明,少量Al4C3对合金铸态组织具有明显的细化作用,而且共晶组织形貌发生明显改变,由完全离异的骨骼状β相共晶组织和共生生长的层片状共晶组织α+β转变为蜂窝状的部分离异共晶组织α+β,同时β相的尺寸变小、分布更趋弥散。通过能谱分析、差热分析以及错配度的计算,证实Al4C3可成为初生α-Mg的良好异质核心。显微组织的细化使强度性能明显提高,延伸率的提高幅度有限,耐腐蚀性能改善。

The effects of Al4C3 on the microstructure and performances of AZ91D alloy are studied by using SEM, EDS, EDS and DTA. It is found that a small amount Al4C3 addition to AZ91 D magnesium alloy leads to the a-Mg grain size obvious decreasing, causes the eutectic microstructure morphology marked change from the fully-divorced β eutectic phase and lamellar α＋β eutectic structure to honeycomb partially-divorced α＋β eutectic structure, and the fl-phases diminution of size and tendency to dispersed distribution. Based on the analysis of EDS, DTA and the calculation of disregistry between Al4C3 and Mg, it is found that the Al4C3 particles can act as the heterogeneous nuclei. The strength properties are significantly improved due to the microstructural refinement of AZ91D alloy, but a little change of elongation percentage, and slight increase of corrosion resistance.