Y(0.3at%)对Ti-45Al-5Nb合金铸态显微组织的影响

Effect of Rare Earth Y (0.3 at%) on as-Cast Microstructure of Ti-45Al-5Nb Alloy

研究了Ti-45Al-5Nb(at%)和Ti-45Al-5Nb-0.3Y(at%)合金的铸态显微组织。结果表明:稀土Y的添加改变了Ti-45Al-5Nb合金的铸态显微组织,促进了等轴晶粒的形成,极大地细化了晶粒;稀土Y主要富集在等轴晶粒的晶界处,并呈断续网络状分布,还有极少量的稀土呈小颗粒分布在晶粒内部;与Ti-45Al-5Nb合金相比,Ti-45Al-5Nb-0.3Y合金除了γ和α2相外,还形成了富集Al和Y的富稀土相—YAl2相;在合金凝固过程中,稀土Y能够提高TiAl合金的形核率,同时稀土Y在固液界面前沿的富集抑制了初生β相的生长,并且后者对晶粒的细化起主要作用。

As-cast microstructures of the Ti-45Al-5Nb （at%） and Ti-45Al-5Nb-0.3Y （at%） alloys were investigated. Results show that as-cast microstructure is changed and equiaxed grains are remarkably refined due to the addition of Y. Most Y element accumulates along the grain boundaries with the discontinuous networks and a small amount of Y element distribute inner the grains with the fine particles. A new phase is produced as YAl2 compound. The mechanisms of grain refinement are analyzed, and indicate that Y could promote nucleation of TiAI alloy and greatly suppress the growth of the primary β phase through the enrichment of Y earlier than the solidification. And the latter more contributed to the refinement of microstructure.