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评价了铸造Ti-47.5Al-2.5V-1.0Cr合金定向层片组织在(750～800)℃/(220～350)MPa不同条件下的持久性能,并分别探索了0.2%Zr和0.1%Hf(原子分数)微合金化对其持久性能的影响。结果表明:提高温度和增加应力均使铸造TiAl合金定向层片组织的持久寿命降低,其中试验温度对持久寿命的影响幅度相对更大,在相同应力下(300 MPa),当温度由750℃提高到800℃时,持久寿命降低超过100 h。微量Zr,Hf对铸造TiAl合金层片组织的择优取向特征均没有影响,对合金的持久寿命改善作用与温度、应力密切相关,例如800℃/220 MPa较低应力下添加微量Zr使合金的持久寿命由150 h提高到320 h,然而在750℃/350 MPa,800℃/260 MPa,300 MPa等较高应力载荷下,微量Zr,Hf的作用明显减小。由试验应力与Larson-Miller参数的关系可发现,与微量Hf相比,微量Zr在不同应力条件下对合金提高持久强度的作用更大。另外,本实验条件下TiAl合金定向层片组织持久塑性均大于10%,无蠕变脆化倾向;添加微量Zr,Hf可使合金在不同温度和应力条件下的持久塑性保持在20%～40%之间,较基础合金更稳定。
The ductility of the oriented ply of Ti-47.5Al-2.5V-1.0Cr alloy cast at (750-800 ℃) / (220-350) MPa was evaluated and the effects of 0.2% Zr and 0.1% Hf (Atomic fraction) microalloying on its long-term performance. The results show that both the increase of temperature and the increase of stress decrease the lasting service life of cast TiAl alloy oriented layer. The influence of test temperature on the life span is relatively larger. Under the same stress (300 MPa), when the temperature is increased from 750 ℃, To 800 ℃, the life expectancy decreased more than 100 h. The trace Zr and Hf have no influence on the preferred orientation of the TiAl alloy cast slab. The improvement of the durable life of the alloy is closely related to the temperature and the stress. For example, adding a small amount of Zr at 800 ℃ / 220 MPa under low stress makes the alloy durable However, the effect of Zr and Hf on Zr and Hf decreases evidently under higher stress loads of 750 ℃ / 350 MPa, 800 ℃ / 260 MPa and 300 MPa. From the relationship between experimental stress and Larson-Miller parameter, it can be found that the micro-Zr has a greater effect on the durability of the alloy under different stress conditions than the micro-Hf. In addition, under the experimental conditions, the ductile plasticity of TiAl alloy oriented laminates is greater than 10%, no tendency to creep embrittlement; adding a small amount of Zr, Hf can maintain the ductility of the alloy at 20% -40 under different temperature and stress conditions %, More stable than the base alloy.