利用Mg-20%(质量分数,下同)Ce中间合金对过共晶Mg-Si合金进行变质处理,研究了Ce加入量对该合金中初生Mg2Si相变质效果(主要是形态)的影响规律,并讨论其变质机制.研究结果表明:当加入量达到并超过0.4%以后,稀土Ce可有效变质过共晶Mg-Si合金中的初生Mg2Si相,其形态由粗大树枝晶转变为具有非规则外形的颗粒,且随Ce加入量增加到2.0%,Ce对初生Mg2Si相的变质均未产生明显的过变质现象.变质机理应主要与稀土元素富集于Mg2Si相生长表面并抑制优先生长晶向的生长有关.%The hypereutectic Mg-Si alloy was modified by rare-earth element of Ce using Mg-20％ (mass fraction,the same below)Ce master alloy. The effect of Ce addition content on the modification of the primary Mg2Si crystals and its modification mechanism were investigated in the present study. The results show that the primary Mg2Si crystals could be effectively modified from coarse dendritic morphologies to polygonal particles with irregular shape when the adding content of Ce was increased to over than 0.4 ％. Over modification of the primary Mg2Si crystals was not found even if the Ce content was increased to 2.0％. The modification mechanism should be associated with the enrichment of Ce on the growth facets of the primary Mg2Si crystals. The preferred growth manner of the primary Mg2Si crystals was depressed, while another type of growth, isotropic growth manner, was enhanced in the modified hypereutectic Mg-Si alloy.
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