TiAl-RE合金中稀土相的形成机理

Formation of Rare Earth Rich Phases in TiAl-RE Alloy

在TiAl合金中加入以Ce和La为主要元素的混合稀土得到普通铸态和熔体旋淬法试样。稀土元素以金属间化合物AlCe(AlLa)分别存在于晶粒边界和层片结构之上。本文基于对二元合金平衡相图的分析以及应用Miedema生成热模型对稀土相AlCe(AlLa)的形成进行了分析。结果表明 ,Al元素与Ce和La的亲和力远大于其与Ti之间的亲和力 ,因此 ,TiAl基合金中的富稀土相以AlCe(或AlLa)的形式存在 。

By adding lanthanide mixture(mainly composed of lanthanide and cerium) to TiAl alloy, as-cast and rapidly solidified TiAl-RE(by melt spinning method) samples were obtained. Rare earth rich phases exist as AlCe(AlLa) in grain boundaries and α_2/γ lamella, respectively. Based on the binary alloy phase diagram analysis, Miedema theory(formation heat theory) is employed to explain the formation of rare earth rich phase. The results show that the affinity between Al and Ce (or La) is much larger than that between Al and Ti. Consequently it is believed that the rare-earth rich phases are present in the TiAl alloy dominantly in the form of AlCe (or AlLa).