(华南理工大学 材料科学与工程学院，广州 510640)
摘 要: 利用Mn/Cr复合对15%Mg2Si/再生A356-1.5%Fe基复合材料进行变质处理，利用SEM、EDS、热分析等方法研究Mn/Cr添加量对复合材料中富Fe相形态的影响规律及其机制，并探讨Mn/Cr添加量对复合材料各物相的凝固结晶特性顺序的影响。富Fe相形态随着Mn/Cr添加量的变化而改变，未变质时，富Fe相形态主要为长针状；Cr(1.0%，质量分数)含量较多时，富Fe相形态主要为骨骼状；Cr和Mn含量均为0.5%时，富Fe相形态主要以颗粒状为主，此时变质效果最佳；而当Mn(1.0%)含量较大时，富Fe相形态则主要呈现花瓣状。未变质复合材料凝固结晶顺序为：初生Mg2Si相(649.8 ℃)、α-Fe相(629.8 ℃)、π-Fe相(618.3 ℃)、Al+Mg2Si共晶(578.3 ℃)、Al+Mg2Si+Si三元共晶(556.7 ℃)；随着Mn含量的不断增加，富Fe相的初始形核温度与基体形核温度差增大，其形核生长时间增加，Fe相尺寸不断增大，数目相对减少。
关键字: 富Fe相；Mn/Cr变质；铝基复合材料；凝固过程
（School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China）
Abstract:Mg2Si/Fe-rich recycled A356 Al matrix composites were prepared by direct melt reaction. The effects of Mn/Cr combining additions on morphologies of Fe-rich and solidification sequence of each phase in composites were investigated by SEM and thermal analysis. The results show that the morphologies of Fe-rich phases can be effectively modified with combining additions of Mn and Cr. The Fe-rich phases in the composites mainly assumed needle-like shapes without modification. After being modified by 1.0%Cr，Fe-rich phases are modified into bone-like shapes. When the Mn and Cr contents are both 0.5%, the optimal modification effect is obtained and the morphologies of Fe-rich phases are mainly globular-like shape. However, the Fe-rich phases are mainly characterized by flower-like shapes when the Mn content is high (1.0%Mn, mass fraction). The solidification and crystallization sequence of the 15%Mg2Si/recycled A356-1.5%Fe composites system is as following: primary Mg2Si phase (649.8 ℃), β-Fe phase (629.8 ℃), π-Fe phase (618.3 ℃), Al+Mg2Si binary eutectic (578.3 ℃) and Al+Mg2Si+Si ternary eutectic (556.7 ℃). The difference of nucleation temperature between Fe-rich and Al+Mg2Si binary eutectic increases with the increase of Mn content. As a result, the growth time of Fe-rich phases is prolonged and the size of Fe-rich phase increases under high Mn content.
Key words: Fe-rich phase; Mn/Cr modification; Al matrix composites; solidification process
