Ti-43Al-4Nb-1.5Mo合金包套锻造与热处理过程的微观组织及高温拉伸性能

发布时间：2018-04-30 10:27

本文选题：TiAl合金 + 包套锻造　；参考：《金属学报》2017年09期

【摘要】：对Ti-43Al-4Nb-1.5Mo合金进行包套锻造和后续热处理实验,考察了该过程TiAl合金的热变形行为、流变软化机制以及热处理参数对微观组织和力学性能的影响。结果表明,TiAl合金包套锻造过程的高温流变软化以β相协调变形、片层相变分解、g相内位错滑移以及孪晶诱导的动态再结晶为主,最终组织为残余α_2/γ层片和等轴α_2、γ、B2相的混合组织。随热处理温度的升高,热变形组织由残余α_2/γ层片和多相混合组织转变为α_2/γ层片+γ相组织,在较高的温度下(1300℃)转变为全层片组织。其中,B2相随着溶质扩散程度的增加逐渐消失,残余层片组织发生分解转变为等轴α_2/γ层片团,同时发生γ→α转变,形成全层片组织。对热等静压、锻态和热处理试样的高温(800℃)拉伸性能进行比较,经热处理后获得的全片层组织具有最佳的综合性能,抗拉强度为663 MPa,延伸率达到26%。分析该样品的断裂行为可知,由于存在层片扭曲拉长、微孔钝化以及裂纹曲折延伸的断裂机制,全层片组织具有良好强度-塑性的综合力学性能。另外,热加工过程中(高温)bcc结构B2相能够协调变形,但服役条件下硬脆的B2相作为裂纹源容易引起裂纹萌生,对力学性能极其不利。因此,TiAl合金在热变形和服役过程中需要对组成相进行严格控制,从而获得良好的力学性能。
[Abstract]:The hot deformation behavior, the rheological softening mechanism and the effect of heat treatment parameters on the microstructure and mechanical properties of the Ti-43Al-4Nb-1.5Mo alloy were investigated. The results showed that the high temperature flow softening in the forging process of the TiAl alloy was characterized by the coordination deformation of the beta phase, the decomposition of the lamellar phase transformation, and the g of G. The internal dislocation slip and the twin induced dynamic recrystallization are the main structure, and the final microstructure is the mixed structure of the residual alpha _2/ gamma layer and the equiaxed alpha _2, gamma, B2 phase. With the increase of heat treatment temperature, the thermal deformed tissue is transformed from the residual alpha _2/ lamella and polyphase mixture to the alpha _2/ gamma layer + gamma phase tissue, and at a higher temperature (1300 degrees C) to the whole layer. Among them, B2 is gradually disappearing with the increase of the degree of solute diffusion, and the decomposition of the residual layer is transformed into an isoaxial alpha _2/ gamma layer mass, and the whole layer tissue is formed by gamma to alpha transformation. The tensile properties of the hot isostatic pressure, forged and heat treated specimens are compared, and the whole layer tissue obtained after heat treatment is obtained. With the best comprehensive properties, the tensile strength is 663 MPa, and the elongation reaches 26%. analysis of the fracture behavior of the sample. It is known that the whole layer tissue has good strength and plastic comprehensive mechanical properties because of the existence of lamellar distortion lengthening, microvoid passivation and the zigzag extension of the crack. In addition, the B2 phase of the bcc structure during hot processing (high temperature) is in the process of heat processing. It can coordinate deformation, but the hard and brittle B2 phase as a crack source can cause crack initiation easily under service conditions, and it is extremely unfavorable to mechanical properties. Therefore, TiAl alloy needs to strictly control the composition phase in the process of thermal deformation and service, so as to obtain good mechanical properties.

【作者单位】：东北大学轧制技术与连轧自动化国家重点实验室;东北大学材料科学与工程学院;
【基金】：国家重点研发计划项目Nos.2016YFB0301200和2016YFB0300603 国家自然科学基金项目No.51504060 中央高校基本科研业务费项目No.N140703003 辽宁省科技项目博士启动基金项目No.201501150~~
【分类号】：TG146.23;TG166.5;TG316

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