论文标题
第一原理计算中Ti-Ta合金的弹性性能的趋势
Trends in elastic properties of Ti-Ta alloys from first-principles calculations
论文作者
论文摘要
马氏体开始温度（$ m _ {\ text {s}} $）是高温形状内存合金的技术基本特征。我们最近显示了[物理学。 Rev. B 94，224104（2016）]，描述$ M_ \ Text {S} $的组成依赖性的两个关键特征是$ t = 0 $ k相位稳定性和振动熵的差异，在Debye模型中，该熵的差异直接链接到弹性属性。在这里，我们将密度功能理论与特殊的准随机结构一起使用，以研究无序的马氏体和奥氏体TI-TA合金的弹性特性作为组成的函数。我们观察到在低ta含量下的奥氏体相的四方剪切弹性常数和\ emph {non-linear}行为中的柔软弹性常数在马丁石的剪切弹性常数中的行为。至少需要12.5 $ \％$ TA才能稳定奥斯丁人们的阶段在$ t = 0 $ k。此外，剪切弹性常数和杨氏模量在接近30 $ \％$的TA浓度上显示出最大的TA浓度。现象学，基于弹性常规的标准表明，添加TA可以增强强度，但会降低合金的延展性特征。此外，随着TA含量的增加，针对马氏体和奥氏体计算的定向弹性刚度变得更加各向同性。弹性性能随组成的函数的报告趋势可以作为在这种有趣类材料中具有优化特性的合金设计的指南。
The martensitic start temperature ($M_{\text{s}}$) is a technologically fundamental characteristic of high-temperature shape memory alloys. We have recently shown [Phys. Rev. B 94, 224104 (2016)] that the two key features in describing the composition dependence of $M_\text{s}$ are the $T=0$ K phase stability and the difference in vibrational entropy which, within the Debye model, is directly linked to the elastic properties. Here, we use density functional theory together with special quasi-random structures to study the elastic properties of disordered martensite and austenite Ti-Ta alloys as a function of composition. We observe a softening in the tetragonal shear elastic constant of the austenite phase at low Ta content and a \emph{non-linear} behavior in the shear elastic constant of the martensite. A minimum of 12.5$\%$ Ta is required to stabilize the austenite phase at $T = 0$ K. Further, the shear elastic constants and Young's modulus of martensite exhibit a maximum for Ta concentrations close to 30$\%$. Phenomenological, elastic-constant-based criteria suggest that the addition of Ta enhances the strength, but reduces the ductile character of the alloys. In addition, the directional elastic stiffness, calculated for both martensite and austenite, becomes more isotropic with increasing Ta content. The reported trends in elastic properties as a function of composition may serve as a guide in the design of alloys with optimized properties in this interesting class of materials.
