快速凝固AZ91D镁合金组织的研究

Study on Microstructures of Rapidly Solidified AZ91D Magnesium Alloy

用光学显微镜和透射电镜观察了普通凝固和快速凝固AZ91D合金的组织 ,用X射线衍射XRD分析了合金的相组成。结果表明 ,普通凝固AZ91D合金组织由α Mg基体和 β Mg1 7Al1 2 相组成 ,晶粒较粗大 ,而快速凝固AZ91D合金薄带截面组织由靠近辊面的粗大等轴晶区、中部的柱状晶区和自由表面层的细小等轴晶区三部分组成 ,三层组织均为过饱和α Mg固溶体 ,并观察到较高的位错密度。

Microstructures of conventionally solidified and rapidly solidified AZ91D magnesium alloy were observed by optical microscope (OM) and transmission electron microscope (TEM). Meanwhile, the phases of the alloy were analyzed by X-ray diffraction (XRD). The results show that the microstructure of conventionally solidified AZ91D alloy is composed of α-Mg matrix and β-Mg17Al12 phase and the grains are coarse. Different microstructures are observed on the cross section of rapidly solidified AZ91D alloy, which are coarse equiaxed grain region closed to the copper roll side, fine equiaxed grain region in the free surface layer and columnar grain region between the both, and all the microstructures are supersaturated α-Mg solid solution with higher dislocation density.