稀土Er对共晶铝铁合金的变质作用

Modification effect of Er on eutectic aluminum-iron alloy

采用热分析方法研究了稀土Er对共晶铝铁合金的变质作用。通过OM、XRD、SEM、EDS以及合金在凝固过程中的特征参数综合分析了稀土Er对共晶铝铁合金的作用机理。结果表明:冷却速率为33℃/s时,共晶铝铁合金的凝固过程为:先发生L→α-Al初转变,然后发生L→Al+Al3Fe和L→Al+Al6Fe共晶转变,添加了稀土Er后,在凝固末期发生L→Al+Al3Er转变而生成铝稀土共晶相。初生的Al3Er可以作为初晶α-Al的非均质形核质点,增加了初晶α-Al的形核率,提高了铝铁合金中初晶α-Al开始形核温度,缩短了共晶转变时间。当Er添加量为0.3wt%时,初晶α-Al平均晶粒尺寸达到了最小值21.7μm。当Er添加量为0.5wt%时,初晶α-Al晶粒尺寸增大,且出现了离异共晶组织。

The modification effect of rare earth Er on eutectic Al-Fe alloy was studied with thermal analysis.The mechanism of rare earth Er on eutectic Al-Fe alloy was comprehensively analyzed by means of OM,XRD,SEM,EDS and characteristic parameters during solidification.The results show that when the cooling rate is 33℃/s,the solidification process of eutectic Al-Fe alloy as follows:L→α-Al occurs first,then the eutectic transformation of L→Al+Al3Fe and L→Al+Al6Fe occur.The addition of rare earth Er results in the transformation of L→Al+Al3Er at the end of solidification.A small amount of Al-RE eutectic is formed.The primary Al3Er can be used as heterogeneous nucleation particle of primaryα-Al,which increases the nucleation rate of primaryα-Al,increases the initial nucleation temperature of primaryα-Al in Al-Fe alloy and shortens the eutectic transformation time.The average grain size of primaryα-Al reaches the minimum of 21.7μm as Er content is 0.3wt%.When Er content is 0.5wt%,the grain size of primaryα-Al increases and the divorced eutectic appears.