采用TEM和XRD分析技术研究了快速凝固AZ91D镁合金的相结构及位错.实验发现,在急冷快速凝固条件下,AZ91D镁合金惯常发生的L?α-Mg+Mg17Al12共晶反应在很大程度上被抑制,形成了以过饱和的α-Mg为主相的快速凝固组织.凝固组织由尺寸为0.8 μm～6 μm的α-Mg晶粒、离散分布于晶内和晶界上的尺度在5 nm～70 nm之间的少量的椭球形Mg17Al12和极少量的多角形Al8Mn5颗粒、以及弥散分布于晶内的非常细小的不规则形态β-AlMg相组成. β-AlMg相为从α-Mg晶内过饱和析出的、逐步向Mg17Al12相过渡的亚稳定组态.在α-Mg晶粒内存在着大量的位错缠结和位错胞,位错胞尺寸在0.2 μm～0.74 μm之间;高密度位错主要存在于在α-Mg 的(002)密排晶面上,且呈现出明显的方向性.
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