Evolution of microstructure and variations in mechanical properties accompanied with diffusionless isothermal ω transformation in β-titanium alloys
Evolution of microstructure and variations in mechanical properties accompanied with diffusionless isothermal ω transformation in β-titanium alloys
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β-钛合金中伴随无扩散等温ω转变的显微组织演变和力学性能变化
DOI：
10.1103/physrevmaterials.4.123603
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发表时间：
2020
影响因子：
3.4
通讯作者：
T. Ichitsubo
中科院分区：
文献类型：
--
作者：
N.L. Okamoto;S. Kasatani;M. Luckabauer;R. Enzinger;S. Tsutsui;M. Tane;T. Ichitsubo
最近在Phys.Rev.Materials.3，043604（2019）2475-995310.1103/PhysRevMaterials.3.043604中定义的无扩散等温omega（）转变被分类为除了众所周知的等温和非热模式之外的第三类转变模式。本文揭示了钛钒合金系相变的特征，着重研究了相变过程中组织和力学性能的变化。Ti-15at%V、Ti-21at%V和Ti-27at%V合金从稳定温度淬火至室温以下后，除Ti-15at%V发生热转变外，在373 K时效时，所有合金均逐渐发生热转变，硬度略有增加。在这些合金中的硬度增加的程度可以成功地解释了淬火热浓度波动的基础上的局部不稳定性的概念。低温时效后，合金的内耗（Ti-21at%V）减小，表明这种不稳定区消失，出现了动态的对崩塌，形成了一个过渡相。非弹性X射线散射和超声测量的比较表明，即使在Ti-27at%V合金中也存在相变的痕迹，该合金没有明显的非热ω相变温度。最后根据计算结果讨论了绝热变换和相变的区别。
Diffusionless isothermal omega () transformation, which was recently defined in Phys. Rev. Materials 3, 043604 (2019)2475-995310.1103/PhysRevMaterials.3.043604, is classified into a third category of thetransformation modes, other than the well-known isothermal and athermal modes. This work reveals the characteristic features of thetransformation in the-titanium vanadium alloy system, specifically, focusing on variations in the microstructure and mechanical properties with the proceeding of thetransformation. After quenching alloys of Ti-15at%V, Ti-21at%V, and Ti-27at%V down to below room temperature from the-stable temperature, in addition to the occurrence of the athermaltransformation for Ti-15at%V, all of the alloys gradually undergo thetransformation upon aging at a temperature as low as 373 K, leading to a moderate increase in the hardness. The degree of the hardness increase in these alloys can be successfully explained by a local instability concept based on quenched-in thermal concentration fluctuations. It is also shown that internal friction (Ti-21at%V) diminishes after the low-temperature aging, which indicates the annihilation of such unstable regions showing a dynamic collapse ofpairs to form a transientphase. Comparison of inelastic x-ray scattering and ultrasound measurements can see a trail of thetransformation remaining even in the Ti-27at%V alloy, which has no obvious athermal omega transformation temperature. Based on the results, the difference between athermalandtransformations is finally discussed.