Effect of cooling rates on as-cast microstructures of Mg-9Al-xSi (x=1, 3) alloys

来源期刊：中国有色金属学报(英文版)2010年增刊第2期

论文作者：李新林 陈彦宾 王香 马国睿

文章页码：393 - 396

Key words：Mg-Al-Si alloys; Mg₂Si; modification; cooling rates; microstructure

Abstract: The effects of cooling rates corresponding to different diameters of the steel mould and laser surface melting (LSM) on the as-cast microstructures of Mg-9Al-xSi (x=1, 3) (mass fraction, %) alloys were investigated by XRD and OM. The results show that obvious refinement of the alloy microstructure is obtained with increasing cooling rate by conventional ingot metallurgy. However, no evident modified morphologies of both dendritic primary Mg₂Si and Chinese script eutectic Mg₂Si in the Mg-Al-Si alloy occurs. Surprisingly, the morphologies of Mg₂Si phases within the laser-melted Mg-Al-Si alloy transform drastically from both coarse Chinese script shape for the eutectic Mg₂Si and dendrite for the primary Mg₂Si to fine spherical particles with an average size of about 3 μm due to the rapid cooling of the melted layer, and the Mg₂Si particulates distribute more uniformly in the α-Mg matrix.