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arXiv 2109.02641cond-mat.mtrl-sci
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钼基难熔多主元合金的伪弹性变形

Pseudoelastic deformation in Mo-based refractory multi-principal element alloys

Aayush Sharma, Prashant Singh, Tanner Kirk, Velary I. Levitas, Peter K. Liaw, Ganesh Balasubramanian, Raymundo Arroyave, Duane D Johnson

摘要:

由密度泛函理论方法支持的相图对于设计作为多主元素$-$合金的子集的高熵合金是至关重要的。我们提出了五元(MoW)$_{x}$ Zr $_{y}$(TaTi)$_{1-x-y}$耐火高熵合金的相和性能分析相结合的计算相图(CALPHAD)和密度泛函理论的结果,辅以分子动力学模拟。通过计算和密度泛函理论相稳定性分析表明,该五元体的富钼钨区具有稳定的单相体心立方结构。我们报道了具有伪弹性行为的Mo $-$ W $-$ Ta $-$ Ti $-$ Zr合金族的第一个五元组成,即,应力滞后$-$应变。我们的分析表明,只有Mo $-$ W $-$富含Mo $-$ W $-$ Ta $-$ Ti $-$ Zr的成分,即,Mo $+$ W $\ge$ 85原子%,显示出在应力-应变中可再现的滞后现象,这是伪弹性行为的原因。基于温度依赖性相图分析和分子动力学模拟预测的弹性行为(其揭示了孪生辅助的伪弹性行为),对(MoW)$_{85}$ Zr $_{7.5}$(TaTi)$_{7.5}$进行下选择。虽然在体心立方晶体中大多未被探索,但孪生是晶体固体中与位错滑移竞争的基本变形机制。该合金在单轴$\lt$ 100 $\gt$加载期间显示出相同的循环变形特征,即,伪弹性在加载方向上是各向同性的。此外,从77到1500 K的温度升高增强了加载-卸载循环中的弹性应变恢复,提供了可能的控制来调整伪弹性行为。

英文摘要:

Phase diagrams supported by density functional theory methods can be crucial for designing high-entropy alloys that are subset of multi-principal$-$element alloys. We present phase and property analysis of quinary (MoW)$_{x}$Zr$_{y}$(TaTi)$_{1-x-y}$ refractory high-entropy alloys from combined Calculation of Phase Diagram (CALPHAD) and density-functional theory results, supplemented by molecular dynamics simulations. Both CALPHAD and density-functional theory analysis of phase stability indicates a Mo-W-rich region of this quinary has a stable single-phase body-centered-cubic structure. We report first quinary composition from Mo$-$W$-$Ta$-$Ti$-$Zr family of alloy with pseudo-elastic behavior, i.e., hysteresis in stress$-$strain. Our analysis shows that only Mo$-$W$-$rich compositions of Mo$-$W$-$Ta$-$Ti$-$Zr, i.e., Mo$+$W$\ge$ 85 at.%, show reproducible hysteresis in stress-strain responsible for pseudo-elastic behavior. The (MoW)$_{85}$Zr$_{7.5}$(TaTi)$_{7.5}$ was down-selected based on temperature-dependent phase diagram analysis and molecular dynamics simulations predicted elastic behavior that reveals twinning assisted pseudoelastic behavior. While mostly unexplored in body-centered-cubic crystals, twinning is a fundamental deformation mechanism that competes against dislocation slip in crystalline solids. This alloy shows identical cyclic deformation characteristics during uniaxial $\lt$100$\gt$ loading, i.e., the pseudoelasticity is isotropic in loading direction. Additionally, a temperature increase from 77 to 1500 K enhances the elastic strain recovery in load-unload cycles, offering possibly control to tune the pseudoelastic behavior.

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