Compositionally complex alloys (CCAs) have attracted significant attention over the past decade due to their potential for exhibiting excellent mechanical properties even at elevated temperatures. The resistance to creep deformation at temperatures greater than one-half of the melting point is primarily driven by atomic diffusion, but experimental measurement of the diffusion coefficients at elevated temperatures is challenging due to the instrumentation limitations and possible oxidation of the alloy. We employ molecular dynamics simulations and first-principles calculations to examine the atomic diffusion of the various elemental species in a refractory CCA containing Mo-Ta-Ti-W-Zr as the constituents. The predictions reveal that diffusion coefficients in CCAs are slower than the corresponding diffusion in the pure metals by a factor of ~8–12, while the activation energies for the diffusion are relatively much higher. A strong attraction between unlike atomic pairs in the CCA coupled with the occurrences of low energy atomic traps due to preferential site-occupancy of the elements creates an ~1 eV energy barrier that significantly impedes atom migration. The sluggish diffusion reduces the creep deformation strain rates, increasing the resistance to creep for the CCA at high temperatures.

在过去的十年中，由于成分复杂的合金（CCA）即使在高温下仍具有出色的机械性能，因此备受关注。在大于熔点一半的温度下，抗蠕变变形的能力主要是由原子扩散驱动的，但是由于仪器的限制和合金的可能氧化，在高温下对扩散系数进行实验测量是一项挑战。我们采用分子动力学模拟和第一性原理计算来检查各种元素物种在以Mo-Ta-Ti-W-Zr为成分的难熔CCA中的原子扩散。这些预测表明，CCA中的扩散系数比纯金属中的相应扩散慢了约8-12倍，而扩散的活化能要高得多。CCA中不同原子对之间的强吸引力以及由于元素优先占据位点而导致的低能原子陷阱的产生会产生〜1 eV能垒，从而显着阻碍原子迁移。缓慢的扩散降低了蠕变变形应变率，从而提高了CCA在高温下的抗蠕变性。