Abstract Uniaxial forging (UAF) and multiaxial forging (MAF) were conducted on a Ti-45Al-7Nb-0.3W (at. %) alloy produced by powder metallurgy (PM) technique, and the deformed microstructures and deformation mechanism were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that the near-gamma microstructure (NG) transformed into a fine and uniform duplex microstructure (DP) after MAF, and the mean grain size of the multiaxial forged alloy was 5 μm. The microstructure of the uniaxial forged alloy was inhomogeneous and anisotropy, while the microstructure of multiaxial forged alloy was very uniform and a higher amount of the β phase was distributed at the grain boundaries. During forging, deformation induced microstructure changes include dislocation movements, mechanical twinning, layer decomposition and dynamic recrystallization (DRX). The DRX occurred repeatedly and more severely during MAF than UAF process. Correspondingly, the multiaxial forged TiAl alloy exhibited excellent high temperature mechanical properties compared to the uniaxial forged alloy. At a temperature of 750 °C, the yield strength, ultimate tensile strength and elongation of the multiaxial forged alloy were 623 MPa, 697 MPa and 4.5%, respectively. It was noteworthy that the multiaxial forged alloy achieved highly plastic deformation and the elongation reached 173% at 900 °C with a strain rate of 1 × 10−3 s−1.

中文翻译：

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多轴锻造对粉末冶金Ti-45Al-7Nb-0.3W合金组织和高温力学性能的影响

摘要 对粉末冶金 (PM) 技术生产的 Ti-45Al-7Nb-0.3W (at. %) 合金进行单轴锻造 (UAF) 和多轴锻造 (MAF)，并通过扫描研究了变形组织和变形机制。电子显微镜 (SEM) 和透射电子显微镜 (TEM)。结果表明，MAF后近伽马显微组织（NG）转变为精细均匀的双相组织（DP），多轴锻造合金的平均晶粒尺寸为5 μm。单轴锻造合金的显微组织不均匀且具有各向异性，而多轴锻造合金的显微组织非常均匀，大量的β相分布在晶界处。在锻造过程中，变形引起的微观结构变化包括位错运动、机械孪生、层分解和动态再结晶 (DRX)。在 MAF 过程中 DRX 重复发生并且比 UAF 过程更严重。相应地，与单轴锻造合金相比，多轴锻造TiAl合金表现出优异的高温机械性能。在750℃的温度下，多轴锻造合金的屈服强度、极限抗拉强度和延伸率分别为623 MPa、697 MPa和4.5%。值得注意的是，多轴锻造合金实现了高塑性变形，在 900°C 时伸长率为 173%，应变率为 1×10-3 s-1。与单轴锻造合金相比，多轴锻造 TiAl 合金表现出优异的高温机械性能。在750℃的温度下，多轴锻造合金的屈服强度、极限抗拉强度和伸长率分别为623 MPa、697 MPa和4.5%。值得注意的是，多轴锻造合金实现了高塑性变形，在 900°C 时伸长率为 173%，应变率为 1×10-3 s-1。与单轴锻造合金相比，多轴锻造 TiAl 合金表现出优异的高温机械性能。在750℃的温度下，多轴锻造合金的屈服强度、极限抗拉强度和伸长率分别为623 MPa、697 MPa和4.5%。值得注意的是，多轴锻造合金实现了高塑性变形，在 900°C 时伸长率为 173%，应变率为 1×10-3 s-1。