MnCO_3细化Mg-Al系铸造合金晶粒的机理

Grain Refinement Mechanism of Cast Mg-Al Alloys with MnCO_3 Additions

在Mg-Al合金熔体中添加MnCO_3细化剂,研究了MnCO_3对铸造Mg-Al系合金晶粒尺寸的影响,并运用"边-边匹配"模型结合热力学与微观组织的分析,探讨了其细化机制。结果表明,MnCO_3对铸造Mg-Al合金晶粒有明显的细化作用,且对AZ31合金的细化效果最好。通过"边-边匹配"模型计算及热力学分析可知,经MnCO_3变质后,镁液中有可能生成Al_4C_3、τ-AlMn化合物,这些化合物与Mg有多对晶体学位向关系,可以作为α-Mg的有效形核质点。

The effects of MnCO3 addition on grain size of the cast Mg-Al alloys were investigated by adding the refiner into the melt,and the refinement mechanism was described by using the edge-to-edge matching model combined with thermodynamics and microstructure analysis.It can be found that MnCO3 has significant refining effect on grain size in as-cast Mg-Al alloys,especially for AZ31 alloy.Based on calculation of the edge-to-edge matching model and thermodynamics analysis of microstructure,the Al4C3andτ-AlMn phase can be generated from molten magnesium alloys modified by MnCO3,which exhibit multiple pairs of ORs with Mg as the potential nucleus of Mg grain.