Sr对过共晶Mg-Si合金中初生Mg_2Si相变质的影响  

Effects of Strontium on Modification of Primary Mg_2Si Phases in Hypereutectic Mg-Si Alloy

作　　者：吴华懂[1] 杜军[1] 豆琦[1] 李伟[1] 

机构地区：[1]华南理工大学材料科学与工程学院

出　　处：《铸造》2011年第4期368-371,共4页Foundry

基　　金：华南理工大学学生研究计划(SRP)项目;广东省大学生创新实验项目

摘　　要：利用Mg-20%Sr中间合金对过共晶Mg-Si合金进行变质处理,对比研究了碱土元素Sr加入量对Mg2Si初晶变质效果(主要包括形态和尺寸)的影响规律,并讨论其变质机制。研究结果表明:碱土元素Sr对过共晶Mg-Si合金中的Mg2Si初晶可有效变质。随着Sr含量的增加,Mg2Si初晶的平均尺寸和尺寸分布范围均逐渐降低,其形态由粗大树枝状晶、细小树枝晶、非规则外形颗粒到规则外形颗粒逐渐过渡。当Sr含量达到2.0%,此时Mg2Si初晶主要呈现为规则外形,平均尺寸为50μm左右。其变质机理应主要与碱土元素富集于Mg2Si相生长表面并抑制优先生长晶向的生长有关。The hypereutectic Mg-4.8%Si alloy was modified by alkaline-earth element Sr through addition of Mg-20%Sr master alloy.The effect of Sr addition amount on the modification of the primary Mg2Si phases and the modification mechanism were investigated.The results show that the primary Mg2Si phases were effectively modified by Sr addition.The average size of the primary Mg2Si phases and their size distribution range were decreased with increase of Sr addition amount;the primary Mg2Si phases change gradually from coarse dendrites for the unmodified Mg-4.8%Si alloy to fine dentrites,particles with irregular shape and then to particles with regular shape.When 2.0%Sr is added,the primary Mg2Si phases are mainly regular-shaped particles with an average size of about 50 μm.The modification mechanism should be associated with the enrichment of Sr on the growth facets of the primary Mg2Si phases.The preferred growth manner of the primary Mg2Si phases was depressed,while another type of growth,isotropic growth manner,was enhanced in the modified alloy.

关 键 词：过共晶Mg-Si合金 碱土金属 变质 Mg2Si初晶 

分 类 号：TG146.22[一般工业技术—材料科学与工程]