Abstract

The paper reports on a nanoindentation study of the hardness H and Young’s modulus E in the B2 phase of quasi-binary TiNi-TiFe single crystals and Ti₄₉Ni₅₁ single and polycrystals with and with no thermoelastic martensite transformations. The study shows that the elastic properties of the alloy single crystals depend on the concentration of Fe atoms and decrease gradually with a decrease in the Fe content and with a gradual decrease in the B2-phase stability to martensite transformations. In Ti₅₀Ni_50–xFe_x, the dependence of the hardness H on the Fe content reveals a peak at equal Fe and Ni concentrations (25.0 at %), which is likely because the alloy at this Fe/Ni ratio is involved in its maximum solid solution hardening. The experimental results are compared with numerical data obtained by the Voigt averaging of elastic constants, showing a mean deviation of 11.55% between them. An analysis of the H and E correlation and the H/E ratio in the alloys as they lose the B2-phase stability to martensite transformations suggests that the correlation coefficient of E and H in TiNiFe measures 0.42, which corresponds to the range of moderate statistical values. In TiNi-TiFe with martensite transformation, the ratio H/E is higher than 0.035, and hence, higher than the values typical of metals and alloys. In our opinion, this is because the elastic moduli of the alloys are “softened” as they get close in concentration to the points of B2 → R → B19′ transitions. The H/E ratio in the alloys can be considered as a criterion of B2-phase stability loss with respect to martensite transformations.

中文翻译：

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TiNi-TiFe单晶和多晶的纳米硬度和弹性模量

摘要

该论文报告了准二元 TiNi-TiFe 单晶和 Ti ₄₉ Ni ₅₁单晶和多晶的B2 相的硬度H和杨氏模量E的纳米压痕研究，有和没有热弹性马氏体转变。研究表明，合金单晶的弹性性能取决于Fe原子的浓度，并随着Fe含量的降低和B2相马氏体相变稳定性的逐渐降低而逐渐降低。在 Ti ₅₀ Ni _{50– x} Fe _x中，硬度H的依赖性对 Fe 含量的分析揭示了在相同的 Fe 和 Ni 浓度（25.0 at %）处出现峰值，这可能是因为在该 Fe/Ni 比率下的合金参与了其最大固溶体硬化。将实验结果与弹性常数的Voigt平均得到的数值数据进行比较，表明两者之间的平均偏差为11.55%。当合金失去马氏体转变的 B2 相稳定性时，对H和E相关性和H / E比的分析表明，TiNiFe 中E和H的相关系数为 0.42，这对应于适度统计范围值。在具有马氏体相变的 TiNi-TiFe 中，比率H / E高于 0.035，因此高于金属和合金的典型值。我们认为，这是因为合金的弹性模量在接近 B2 → R → B19' 转变点时被“软化”。合金中的H / E比值可被视为关于马氏体转变的 B2 相稳定性损失的标准。