针对增压器涡轮应用背景,详细分析定向层片组织铸造TiAl合金的室温拉伸塑性、断裂韧度以及高温热暴露后的剩余塑性等反映叶片抗损伤能力的性能,并讨论在叶片中形成这种定向层片组织的工艺可行性,以获得一种有利于增压器涡轮可靠性的组织设计.结果表明:定向层片组织铸造TiAl合金具有优异的室温拉伸塑性和断裂韧度,并且在高温热暴露后仍能保持较高的室温拉伸塑性,这些优异性能均依赖于定向层片取向一致性特征.通过控制凝固冷却条件和Ti/Al原子比,在增压器涡轮叶片中可以获得层片界面近似平行叶片表面的定向层片组织,有利于提高叶片的抗损伤能力,从而改善TiAl合金增压器涡轮的使用可靠性.
Based on the application background of turbocharger wheel, the mechanical properties reflecting the damage resistance of turbocharger wheel blade, including RT ductility and fracture toughness together with residual RT ductility after thermal exposure were analyzed in details for a cast TiAl alloy with the directional lamellar microstructure, and the feasibility of cast process for obtaining this microstructure in the blade was also discussed, upon which a new idea of microstructure design was proposed for the reliability of turbocharger wheel.The results indicate that the directional lamellar structure exhibits excellent RT ductility and fracture toughness, and also can retain relatively higher RT ductility after thermal exposure at high temperature, and these good performances rely on the orientation uniformity of the directional lamellar structure.More importantly, by controlling the cooling condition during solidification and atomic ratio of Ti and Al, this directional lamellar structure with the lamellar boundary nearly parallel to the blade surface can be obtained in the blade of turbocharger wheel.This special structure is good to improve the damage resistance of the blade and the reliability of turbocharger.
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