Y对TiAl合金显微组织及性能的影响

Effects of Yttrium on Microstructure and Properties of TiAl Alloy

系统地研究了Ti-47Al-xY系[x（摩尔分数／％）分别为0、0．1、0．3、0．5、0．7、1．0]合金的显微组织及室温力学性能。结果发现：随着Y含量的增加，合金由柱状晶转变为等轴晶（x≥0．3），而且合金的晶粒尺寸和层片间距随着Y含量的增加而降低；当Y含量高于0．1％时，晶内弥散分布细小YAl2相颗粒的同时，YAl2相开始在晶界处偏析，且随着Y含量的增加，晶界偏析越来越严重；当Y含量达到1．0％时，晶界处YAl2相闭合成网络状。拉伸测试表明，Y含量为0．3％～0．5％的Ti-47Al合金有较高的强度和塑性。分析得知，YAl2相的尺寸及分布对性能起着重要的作用。一方面，组织的细化和晶内细小的YAl2相有利于性能的改善，另一方面，晶界处富集的大尺寸YAl2相显著恶化TiAl合金的性能，特别是在Y含量高于0．5％的TiAl合金中。

Effects of different yttrium contents , such as 0, 0. 1%, 0. 3%, 0. 5%, 0. 7%, 1. 0%, on micro-structure and tensile strength at room temperature of Ti-47Al-xY alloy have been investigated systematically. The results show that with the increase of yttrium content, the columnar crystal in alloy is changed into equiaxed crystal with the yttrium content more than 0. 3%, and the grain size and lamellar space are decreased remarkably. With yttrium content more than 0. 1 % , when fine YA12 particle is uniformly distributed in the grain, some YA12 particles begin to segregate from the boundary in the alloy. Furthermore, the segregation from boundary becomes more and more serious with increasing in Y content. YAl2 phase is closed to form network with 1% Y content. Tensile testing indicates that the Ti-47A1 alloy with 0. 3% -0. 5% Y content possesses higher strength and plasticity. Size and distribution of YA12 phase in the alloy has the significant effects on properties of the alloys. As fined microstructure and fine YA12 phase in the grain is beneficial to improving the properties of the alloy, large YA12 phase enriched in boundary can greatly deteriorate the properties of TiAl alloy, especially Y content more than 0. 5%.