大尺寸锻造β型γ-TiAl合金的显微组织与力学性能分析

Microstructure and mechanical properties of large-size as-forgedβtypeγ-TiAl alloy

β型γ-TiAl合金被广泛应用于复杂零件的制备,但在大尺寸单向锻造过程中显微组织和力学性能表现出显著的不均匀性。通过扫描电子显微镜(SEM)、电子背散射(EBSD)和X射线衍射(XRD)分析了合金的显微组织,关注大尺寸锻造的高β相含量Ti-43Al-9V-0.2Y合金的显微组织和力学性能。研究表明,V元素的添加提高了合金的β相含量,增强了热变形能力。锻造技术在有效变形区形成了细小的等轴晶粒组织,而变形死区则仍保留了部分原始层片结构,中心区域的细小等轴晶粒赋予了合金优异的室温性能,尤其是1.42%的室温塑性。高温力学性能分析显示,Ti-43Al-9V-0.2Y合金在700~750℃范围内经历韧脆转变,在脆性断裂温度下具有较高的强度,主要变形机制为加工硬化。在韧性断裂温度下,合金展现出良好的塑性,主要通过动态再结晶和微孔协调变形来实现。

β-γTiAl alloys are extensively used in the fabrication of complex components,yet they exhibit significant heterogeneity in microstructure and mechanical properties during large-size unidirectional forging.In this study,the microstructure of the alloy was investigated by scanning electron microscopy(SEM),electron backscattering(EBSD)and X-ray diffraction(XRD),focusing on the microstructure and mechanical properties of highβ-phase content Ti-43Al-9V-0.2Y alloys forged in large sizes.It was shown that the addition of vanadium(V)increased theβ-phase content of the alloy,thereby improving thermal deformation capability.The forging technique produced fine equiaxed grain structure in the effective deformation zone,while the dead zone retained part of the original lamellar structure.The fine equiaxed grains in the central region endowed the alloy with excellent room-temperature properties,in particular,a room-temperature plasticity of 1.42%.High-temperature mechanical property analysis revealed that the Ti-43Al-9V-0.2Y alloy undergoes a ductile-to-brittle transition between 700℃~750℃.At temperatures conducive to brittle fracture,the alloy exhibits high strength,primarily due to work hardening;at temperatures favorable for ductile fracture,the alloy demonstrates good ductility,mainly attributed to dynamic recrystallization and microporous coordinated deformation mechanisms.