双辊铸轧AZ31镁合金板坯的物相分析

Phases analysis of twin-roll casting AZ31 Mg alloy plate blank

采用双辊铸轧技术制备AZ31镁合金板坯,利用X射线衍射、金相显微镜、扫描电子显微镜以及能谱分析等技术对该板坯的物相进行分析。结果表明:双辊铸轧AZ31镁合金板坯中的物相主要有α-Mg枝晶、枝晶间富溶质α-Mg和不规则的块状Mg17(Al,Zn)12相组成的离异共晶以及弥散分布于晶内的星形细小Al8Mn5相;在双辊铸轧过程中,随着Mg液温度的降低,过饱和的Mn以Al8Mn5相的形式从Mg液中析出,而后细小的Al8Mn5相随着α-Mg初晶的长大进入枝晶胞内部;α-Mg初晶长大的同时,Al、Zn等元素在枝晶间未凝固的液相中富集,最终在枝晶间形成依附于初晶的富溶质α-Mg和不规则的块状Mg17(Al,Zn)12相组成的离异共晶。

AZ31 Mg alloy plate was fabricated successfully by twin-roll casting technology, and the phases in the plate were analyzed by X-ray diffraction, metallographic microscope, scanning electron micrograph and an energy dispersion X-ray spectroscopy. The results show that the phases of twin-roll casting AZ31 Mg alloy are composed of α-Mg dendritic, divorced eutectic with a-Mg and irregular massive Mg17（Al, Zn）12, and fine star-shaped AlsMns. During the twin-roll casting process, the supersaturated Mn precipitates from the melt in the form of Al8Mn5 phases, and then the little Al8Mn5 phases enter into the dendritic with the a-Mg primary crystals growing up with temperature decreasing. At the same time, Al and Zn enrich in the remaining melt between dendritics, which leading to the formation of the divorced eutectic composed of enriched α-Mg leeching on the primary crystal and irregular massive Mg17（Al, Zn）12 phases in the interdendritic.