(華南理工大學(xué) 材料科學(xué)與工程學(xué)院，廣州 510640)
摘 要: 利用Mn/Cr復(fù)合對15%Mg2Si/再生A356-1.5%Fe基復(fù)合材料進行變質(zhì)處理，利用SEM、EDS、熱分析等方法研究Mn/Cr添加量對復(fù)合材料中富Fe相形態(tài)的影響規(guī)律及其機制，并探討Mn/Cr添加量對復(fù)合材料各物相的凝固結(jié)晶特性順序的影響。富Fe相形態(tài)隨著Mn/Cr添加量的變化而改變，未變質(zhì)時，富Fe相形態(tài)主要為長針狀；Cr(1.0%，質(zhì)量分數(shù))含量較多時，富Fe相形態(tài)主要為骨骼狀；Cr和Mn含量均為0.5%時，富Fe相形態(tài)主要以顆粒狀為主，此時變質(zhì)效果最佳；而當(dāng)Mn(1.0%)含量較大時，富Fe相形態(tài)則主要呈現(xiàn)花瓣狀。未變質(zhì)復(fù)合材料凝固結(jié)晶順序為：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 ℃)；隨著Mn含量的不斷增加，富Fe相的初始形核溫度與基體形核溫度差增大，其形核生長時間增加，F(xiàn)e相尺寸不斷增大，數(shù)目相對減少。
關(guān)鍵字: 富Fe相；Mn/Cr變質(zhì)；鋁基復(fù)合材料；凝固過程
（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，F(xiàn)e-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
