(華中科技大學(xué) 模具技術(shù)國家重點實驗室， 武漢 430074)
摘 要: 金相顯微鏡及電子探針分析結(jié)果表明，含La，Ce的混合稀土和金屬Y均有促進(jìn)AZ91鎂合金鑄態(tài)組織晶粒細(xì)化的作用。在AZ91+(Ce， La)合金中形成的桿狀化合物被證實是(Ce, La)Al4，而在AZ91+Y合金中發(fā)現(xiàn)了呈塊狀結(jié)構(gòu)的YAl2化合物。420℃/20h固溶處理后，由于(Ce, La)Al4及YAl2具有良好的熱穩(wěn)定性，不溶入Mg基體，AZ91+RE(La,Ce,Y)合金的鑄態(tài)組織為δ固溶體+(Ce, La)Al4(或YAl2)化合物+Mg17Al12三相組成。
關(guān)鍵字: AZ91鎂合金； 混合稀土； 釔； 電子探針； 鑄態(tài)組織
as-cast structure of AZ91 alloy
（State Key Laboratory of Die and Mould Technology, Huazhong University of
Science and Technology, Wuhan 430074, P.R.China）
Abstract:The effect of yttrium and mischmetal composed of 50%Ce, 45%La (mass fraction) on the as-cast structure of AZ91 alloy were investigated by optical microscope and electron microprober analysis. The experimental results show that the structure of AZ91 alloy is refined either by mischmetal or Y. The rod-like typed compound is verified as (Ce,La)Al4 in AZ91 alloy with additional mischmetal; but a polyhedral compound is found and identified as YAl2 by EDX analysis in AZ91 alloy with additional Y. Both (Ce,La)Al4 and YAl2 have thermally stable property and do not dissolve into Mg matrix when solution treatment is carried out for 20h at 420℃followed by air quenching. The as-cast structure of AZ91+RE(La,Ce,Y)alloy consists of three phases including Mg matrix, (Ce, La)Al4(or YAl2) and Mg17Al12.
Key words: AZ91 magnesium alloy; mischmetal; yttrium; electron microprober; as-cast structure
