B和Y对高铌TiAl合金组织和拉伸性能的影响

Effects of B and Y Additions on the Microstructure and Tensile Behaviour of High-Nb TiAl Alloys

摘要:

研究了B和Y对Ti45Al8Nb0.2W0.25Cr (at%) 合金的微观结构、微观偏析和拉伸行为的影响。结果表明，高铌TiAl合金中的β相稳定元素促进了微观偏析区域中γ相以及大块状微观偏析区域的形成。具有低比表面积的大块状微偏析区域降低了微偏析界面处的空洞和裂纹的成核率，明显降低了晶界处的强度和合金的抗拉强度。B和Y的添加明显的细化了片层团，增加了片层团处空洞成核的机会，从而提高了变形抗力。分析了2种合金的拉伸机理。

Abstract:

The influence of B and Y on the microstructure, microsegregation, and tensile behaviour of the Ti45Al8Nb0.2W0.25Cr (at%) alloy was investigated. The β-stabilizer elements in the high-Nb TiAl alloy promote the formation of the γ phase in the microsegregation region and lead to the formation of large blocky microsegregation areas. The large blocky microsegregation regions with low specific surface areas reduce the nucleation rate of cavities and cracks at the interfaces of the microsegregation, which are harmful to colony boundary strengthening and decrease tensile resistance. The addition of B and Y affords an obvious refinement in the lamellar colony, renders an increasing opportunity for cavity nucleation at the colony boundary, and thus improves the tensile resistance. The tensile mechanisms of the alloys before and after (B, Y) addition were also compared and analysed.