Lattice distortion and order-disorder phase equilibrium in hcp high-entropy alloys Al-Sc-Ti-Zr-Hf

High entropy alloys (HEA) have been noted for their outstanding mechanical properties as well as outwardly simple crystal structures, which offer in fact many possibilities for tuning mechanical properties through lattice distortions and short-range order. With recent reviews lamenting a lack of detailed crystal structure data, especially at the local scale, this experiment plans to investigate a recently developed refractory HEA and its precursors. High resolution powder diffraction will help determining the phases across its binary, ternary, quinary compositions and, through microstructure analysis, studying the local strain fields that are key to alloy strengthening mechanisms. Distortion and sublattice ordering will be also characterised at the atomic and nano scale by pair-distribution function analysis (PDF).

高熵合金（High Entropy Alloys，HEA）凭借优异的力学性能与表观简洁的晶体结构广受关注，这类结构实则为通过晶格畸变与短程有序调控力学性能提供了诸多可行路径。近期的综述研究均指出，当前领域内缺乏精细化的晶体结构数据，尤以局域尺度下的相关数据缺失为甚。为此，本实验拟对一款新近开发的难熔高熵合金及其前驱体展开研究：采用高分辨粉末衍射技术，确定该合金在二元、三元、五元组分下的物相，并通过微观结构分析，探究作为合金强化机制核心的局域应变场；同时借助配对分布函数分析（Pair-Distribution Function Analysis，PDF），在原子与纳米尺度下对合金的畸变与亚晶格有序性进行表征。