Refractory high entropy superalloys (RHESs), known for their excellent high temperature performance, exhibit promising characteristics but are challenged by significant brittleness. Efforts to enhance plasticity through microstructure regulation have achieved only limited success, largely due to the unclear underlying fracture mechanisms of the superstructure. In this study, we systematically investigate the fracture mechanisms of the AlMo0.5NbTa0.5TiZr RHES from microscopic to electronic scales. Interestingly, both experimental and simulation results reveal that the ordered B2 phase demonstrates non-negligible plastic deformation capabilities during fracture, including deformation twinning and amorphization. Despite this, the fracture resistance of the B2 phase is lower compared to the A2/B2 interface and disordered A2 phase, even though the A2 phase shows less twinning and amorphization. Ab initio molecular dynamics simulations, combined with electronic behavior analysis, indicate that bonds involving Al and Zr in the B2 phase often exist in an anti-bonding state, making them more prone to breaking under load. This study provides deeper insights into the fracture mechanisms of the A2/B2 superstructure and its constituent phases at both atomic and electronic levels, offering a systematic approach to improving the fracture properties of such RHESs.

中文翻译：

---

AlMo0.5NbTa0.5TiZr耐火高熵高温合金断裂的原子机理


难熔高熵高温合金 （RHES） 以其优异的高温性能而闻名，表现出有前途的特性，但受到明显脆性的挑战。通过微观结构调节来提高塑性的努力只取得了有限的成功，这主要是由于上层结构的潜在断裂机制不明确。在这项研究中，我们从微观到电子尺度系统研究了 AlMo0.5NbTa0.5TiZr RHES 的断裂机制。有趣的是，实验和仿真结果都表明，有序 B2 相在断裂过程中表现出不可忽略的塑性变形能力，包括变形孪晶和非晶化。尽管如此，与 A2/B2 界面和无序的 A2 相相比，B2 相的抗断裂性较低，即使 A2 相显示出较少的孪晶和非晶化。从头计算的分子动力学模拟与电子行为分析相结合，表明 B2 相中涉及 Al 和 Zr 的键通常以反键态存在，使其在负载下更容易断裂。本研究在原子和电子水平上对 A2/B2 超结构及其组成相的断裂机制提供了更深入的见解，为改善此类 RHES 的断裂性能提供了一种系统的方法。