保温时间对TiAl基合金组织与力学性能的影响

Effect of Holding Time on Microstructure and Mechanical Properties of TiAl based Alloy

摘要:

TiAl基合金具有低密度、高比强度、高比刚度等优异的高温综合性能,在航空发动机制造中,有望替代密度较大的镍基合金。本文以铸造TiAl合金为研究对象,系统研究了在1523k下不同保温时间内的合金中β₂相的相变规律和其对室温力学性能的影响,实验结果表明：在1523k分别保温5min-4h,然后对铸造态Ti-Al-Nb-Cr-Mo-B合金进行水冷淬火,当保温时间为2h时,韧性没有降低,强度却从1200MPa提升到了1500MPa。在保温过程中α分解为γ＋β相,随后冷却过程中,无序的β相会转变为有序的β₂相。实验结果表明β₂相是一种硬脆相,少量的β₂相能促进合金强度的提升。

Abstract:

The TiAl-based alloy has excellent high-temperature comprehensive properties such as low density, high specific strength and high specific stiffness. It is expected to replace a nickel-based alloy with high density in aero-engine manufacturing. In this paper, the transformation rule of β₂-phase and its effect on the mechanical properties at room temperature in the cast TiAl alloy were studied systematically. The experimental results demonstrated that the toughness of the cast Ti-Al-Nb-Cr-Mo-B alloy is not decreased when the holding time is 2h, but the strength increased from 1200MPa to 1500 MPa. In the process of heat preservation, α decomposes into γ + β phase, and then in the process of cooling, the disordered β phase transforms into ordered β₂ phase. The experimental results show thatβ₂ phase is a hard brittle phase, and a small amount of β₂ phase can promote the strength of the alloy.