Cheng Changjun, Feng Renfei, Lyu Tianyi, Zou Yu
Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario, M5S 3E4, Canada.
Canadian Light Source, Saskatoon, Saskatchewan, S7N 2V3, Canada.
Adv Mater. 2024 Aug;36(31):e2403632. doi: 10.1002/adma.202403632. Epub 2024 Jun 16.
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)(NbTa) 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 is 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 the understanding of thermal stability but also delves into the onset of crystallization in HEA systems.
纳米晶（nc）金属通常强度高但热不稳定，这使得它们难以加工且不适用于某些应用，尤其是在高温下。人们发现，纳米晶多组分和高熵合金（HEA）具有更高的热稳定性，但这仅在大量成分空间中通过经验发现的少数体系中存在。作为回应，这项工作开发了一种组合策略，以加速发现具有不同热稳定性（在相和晶粒尺寸方面）的纳米晶（TiZrHf）（NbTa）合金库。基于同步加速器X射线衍射和电子显微镜表征，观察到退火后从非晶-晶体纳米复合材料向体心立方（bcc）相的相变。随着NbTa含量增加（x值降低），该体系在退火后倾向于形成热稳定的双bcc相；相反，TiZrHf含量增加（x>0.6）的合金保持单组分纳米复合材料状态，阻碍结晶和晶粒生长。这项研究不仅拓宽了对热稳定性的理解，还深入探讨了高熵合金体系中结晶的起始情况。
