钇及铈镧混合稀土对AZ91镁合金铸态组织的影响

Effect of yttrium and mischmetal on as-cast structure of AZ91 alloy

金相显微镜及电子探针分析结果表明 ,含La,Ce的混合稀土和金属Y均有促进AZ91镁合金铸态组织晶粒细化的作用。在AZ91+(Ce ,La)合金中形成的杆状化合物被证实是 (Ce ,La)Al4,而在AZ91+Y合金中发现了呈块状结构的YAl2 化合物。4 2 0℃ / 2 0h固溶处理后 ,由于 (Ce,La)Al4及YAl2 具有良好的热稳定性 ,不溶入Mg基体 ,AZ91+RE(La ,Ce,Y)合金的铸态组织为δ固溶体 +(Ce ,La)Al4(或YAl2 )化合物 +Mg17Al12 三相组成。

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)Al 4 in AZ91 alloy with additional mischmetal; but a polyhedral compound is found and identified as YAl 2 by EDX analysis in AZ91 alloy with additional Y. Both (Ce,La)Al 4 and YAl 2 have thermally stable property and do not dissolve into Mg matrix when solution treatment is carried out for 20?h 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)Al 4 (or YAl 2) and Mg 17 Al 12 . [