Formation process of unique microstructure in rapidly solidified Mg97Zn1Y2 alloy
Formation process of unique microstructure in rapidly solidified Mg97Zn1Y2 alloy
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DOI：
10.1016/j.msea.2003.10.145
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发表时间：
2004-07-15
期刊：
影响因子：
6.4
通讯作者：
Yamamuro, T
中科院分区：
文献类型：
--
作者：
Nishida, M;Kawamura, Y;Yamamuro, T
利用透射电镜（TEM）研究了快速凝固粉末冶金（RS P/M）Mg 97 Zn 1 Y2合金中6 H相的形成过程。RS粉末的初始组织由平均直径约1 μ m的等轴晶组成，其周围是富含Y和Zn的非晶晶界。在以42 m/s的圆周速度制备的RS带中的晶界处观察到6 H相。通过降低圆周速度，RS薄带中晶界处的6 H相转变为非晶相。随着冷却速度的降低，快速凝固Mg 97 Zn 1 Y2合金中Y和Zn的晶界偏聚量增加。也就是说，Y和Zn的富集促进了RS合金晶界相的非晶化。在573 K退火1.2 ks后，6 H相从晶界开始生长。结果表明，快速凝固Mg 97 Zn 1 Y2合金中的6 H相在挤压过程中先在晶界处以富Y和Zn的非晶相形式结晶，然后向晶内生长。为了阐明6 H相的稳定性与热处理，RS薄带的显微组织变化也进行了描述。(C)2003 Elsevier B. V.保留所有权利。
The formation process of 6H-phase in rapidly solidified powder metallurgy (RS P/M) Mg97Zn1Y2 alloy has been investigated by transmission electron microscopy (TEM) observations. The initial microstructure of RS powder consists of equiaxed grains about 1 mum in average diameter which is surrounded by Y and Zn rich amorphous grain boundaries. The 6H-phase was observed at grain boundaries in the RS ribbon prepared at circumferential speed of 42 m/s. By lowering the circumferential speed, the 6H-phase at grain boundary in the RS ribbon changes to amorphous phase. The amount of Y and Zn segregation at the grain boundary in RS Mg97Zn1Y2 alloy increases with decreasing the cooling rate. In other words, the amorphization of grain boundary phase in RS alloy was promoted by the enrichment of Y and Zn. The growth of 6H-phase starts from grain boundary in the RS ribbon annealed at 573 K for 1.2 ks. It can be concluded that the 6H-phase in RS P/M Mg97Zn1Y2 alloy crystallizes in the Y and Zn rich amorphous phase at grain boundary and then grows into grain interior during extrusion. In order to clarify the stability of 6H-phase with heat treatment, microstructure changes in RS ribbon are also described. (C) 2003 Elsevier B.V. All rights reserved.