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对Ti-45Al-8.5Nb(WBY)合金在700℃大气环境下分别进行了1000、1700、3000、10000h的热暴露处理。通过扫描电镜及透射电镜研究了系列热暴露对该合金组织稳定性的影响,并进行了室温拉伸测试。研究发现,Ti-45Al-8.5Nb-(WBY)合金在室温下为双态细晶组织。在热暴露1000 h后,在α2+γ层片晶团内α2层片通过α2→γ相变发生了平行分解,导致层片细化,这有利于提高该合金的拉伸强度,屈服强度和塑性。在热暴露1700h后,合金开始通过α2+γ→B2(ω)相变生成B2(ω)等轴晶粒。在3000h热暴露后,从α2+γ层片晶团形成的B2(ω)等轴晶粒达到18 vol%,而且其上有针状相广泛析出。经历10000h热暴露形成的B2(ω)等轴晶粒和经历3000h形成的接近,导致该合金的强度和塑性均降低,但在10000h热暴露后,这种力学性能的降低不高于10%。
Thermal exposure of Ti-45Al-8.5Nb (WBY) alloy was carried out at 700 ℃ for 1000, 1700, 3000 and 10000h respectively. The effect of thermal exposure on the microstructure of the alloy was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tensile tests at room temperature were carried out. It is found that the Ti-45Al-8.5Nb- (WBY) alloy is a bimodal fine-grained structure at room temperature. After heat exposure for 1000 h, the α2 layer in the α2 + γ lamellae was decomposed in parallel by α2 → γ phase transformation, resulting in the refinement of the lamella, which is beneficial to improve the tensile strength, yield strength and Plasticity. After heat exposure for 1700h, the alloy began to form B2 (ω) equiaxed grains through α2 + γ → B2 (ω) transformation. After thermal exposure at 3000 h, the B2 (ω) equiaxed grains formed from the α2 + γ lamellae reached 18 vol%, and there were extensive precipitation of acicular phases. The B2 (ω) equiaxed grains formed by thermal exposure of 10000h and the formation of close 3000h results in the decrease of strength and ductility of the alloy. However, this mechanical property is reduced by no more than 10% after 10000h heat exposure.