Mg-Zn-Y三元合金富Mg区凝固组织及二十面体准晶相形貌  

Solidification of Mg28Zn2Y and Icosahedral Quasicrystal Morphology Evolution

作　　者：万迪庆[1] 杨根仓[1] 周尧和[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《稀有金属材料与工程》2007年第12期2166-2168,共3页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(50571081);航空基金(04G53024)

摘　　要：通过常规凝固方法在Mg28Zn2Y三元合金中的富Mg区获得了二十面体稳定准晶相。Mg28Zn2Y三元合金铸态组织中存在α-Mg相,Mg7Zn3相和二十面体准晶相。该合金的准晶形貌有两种:一种为尺寸较大、具有五次对称性的花瓣状;另一种为尺寸稍小、对称性不太明显的团状。五次对称性的花瓣状形貌是二十面体准晶,是按其特有的五次对称轴的择优方向自由生长所致。冷却速率直接影响合金凝固过程中准晶熟化时间。熟化时间越长,越容易使准晶花瓣端部粗化以及在端部发生分叉。端部的分叉容易使得花瓣准晶破碎,破碎的准晶游离到低温相中,在界面能的作用下形成多边形形貌。Applying XRD, OM, SEM and TEM techniques, an investigation on the solidification of Mg28Zn2Y quasicrystal alloy was carried out. It is found that α-Mg phase, Mg7Zn3 phase and icosahedral quasicrystal phase coexist in the as-solidified morphology. A perfect five-branch icosahedral quasicrystal morphology was observed. It is attributed to the icosahedral quasicrystal free growth with preferred growth direction of five-fold symmetry axes resulting in five-branch morphology. Furthermore, the effect of cooling rate on the quasi-crystal morphology was also studied. High cooling rate leads to rapid solidification, and in turn, petal-like quasi-crystal morphology is reserved. On the other hand, slow cooling rate favors coarsening and branching of the quasi-crystal, and subsequently, subjected to long curing time, the formation of polygonal quasi-crystals driven by the action of interface energy.

关 键 词：MG-ZN-Y合金 二十面体准晶 形貌特征 冷却速率 

分 类 号：TG111.4[金属学及工艺—物理冶金]