Pieczyska Elżbieta A, Maj Michał, Golasiński Karol, Staszczak Maria, Furuta Tadahiko, Kuramoto Shigeru
Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawińskiego 5 B, Warsaw 02-106, Poland.
Toyota Central Research & Development Laboratories, Inc., Nagakute, Aichi 480-1192, Japan.
Materials (Basel). 2018 Apr 7;11(4):567. doi: 10.3390/ma11040567.
This paper presents results of investigation of multifunctional β-Ti alloy Gum Metal subjected to tension at various strain rates. Digital image correlation was used to determine strain distributions and stress-strain curves, while infrared camera allowed for us to obtain the related temperature characteristics of the specimen during deformation. The mechanical curves completed by the temperature changes were applied to analyze the subsequent stages of the alloy loading. Elastic limit, recoverable strain, and development of the strain localization were studied. It was found that the maximal drop in temperature, which corresponds to the yield limit of solid materials, was referred to a significantly lower strain value in the case of Gum Metal in contrast to its large recoverable strain. The temperature increase proves a dissipative character of the process and is related to presence of and ″ phases induced during the alloy fabrication and their exothermic phase transformations activated under loading. During plastic deformation, both the strain and temperature distributions demonstrate that strain localization for higher strain rates starts nucleating just after the yield limit leading to specimen necking and rupture. Macroscopically, it is exhibited as softening of the stress-strain curve in contrast to the strain hardening observed at lower strain rates.
本文介绍了对多功能β钛合金“牙龈金属”在不同应变速率下进行拉伸试验的研究结果。采用数字图像相关技术来确定应变分布和应力-应变曲线，同时利用红外热像仪获取试样在变形过程中的相关温度特性。通过考虑温度变化的力学曲线来分析合金加载的后续阶段。研究了弹性极限、可恢复应变以及应变局部化的发展情况。结果发现，与较大的可恢复应变相比，对应于固体材料屈服极限的最大温度下降在“牙龈金属”中出现在显著更低的应变值处。温度升高证明了该过程的耗散特性，并且与合金制造过程中诱导产生的α″相的存在以及加载时激活的放热相变有关。在塑性变形过程中，应变和温度分布均表明，对于较高应变速率，应变局部化在屈服极限之后立即开始形核，导致试样颈缩和断裂。从宏观上看，这表现为应力-应变曲线的软化，与较低应变速率下观察到的应变硬化形成对比。
