Accelerated Discovery of (TiZrHf)_x(NbTa)_1−x High‐Entropy Alloys With Superior Thermal Stability and a New Crystallization Mechanism

Abstract

Nanocrystalline (nc) metals are generally strong yet thermally unstable, rendering them difficult to process and unsuitable for use, particularly at elevated temperatures. Nc multicomponent and high‐entropy alloys (HEAs) are found to offer enhanced thermal stability, but only in a few empirically discovered systems out of a vast compositional space. In response, this work develops a combinatorial strategy to accelerate the discovery of nc‐(TiZrHf)x(NbTa)1‐x alloy library with distinct thermal stability, in terms of phases and grain sizes. Based on synchrotron X‐ray diffraction and electron microscopy characterizations, a phase transition was observed from amorphous‐crystalline nanocomposites to a body‐centered cubic (bcc) phase upon annealing. With increased NbTa content (decreased x value), the system tends to achieve thermally stable dual bcc phases upon annealing; in contrast, alloys with increased TiZrHf content (x > 0.6) maintain a single‐composition nanocomposite state, impeding crystallization and grain growth. This investigation not only broadens our understanding of thermal behavior but also delves into the onset of crystallization in HEA systems.This article is protected by copyright. All rights reserved