Enhancing the work hardening capability of lightweight refractory high-entropy alloys via bimodal heterostructure

Lightweight refractory high-entropy alloys (LRHEAs) have garnered significant attention due to their exceptional combination of strength and plasticity. However, their limited work-hardening capability has posed a serious challenge to their engineering applications. In this study, bimodal heterostructure with coexisting coarse and fine grains were induced in TiZrVNbAl LRHEAs by controlling treatment processes, and the work-hardening behavior of these alloys was investigated. During the tension deformation, heterogeneous structured alloys can gradually produce amounts of geometrically necessary dislocations (GNDs), which is almost an order of magnitude higher than that in the homogeneous alloys at the same deformation degree. The continuous increase of GNDs can not only generate obvious hetero-deformation-induced (HDI) stress in the heterogeneous structure (contributing more than 60 % to the total stress), but also increase the possibility of interaction events between dislocations, result in enhanced deformation uniformity. Ultimately, benefiting from the bimodal heterostructure, the work hardening capability of the heterogeneous structured alloy increased ∼400 % compared to the homogeneous alloy (from 400 to 2000 MPa). Due to the high work-hardening rate, the uniform elongation of the LRHEAs was significantly increased from less than 2 % to ∼13 %, and the yield strength also saw an obvious increase. This study presents a novel strategy for developing new lightweight alloys with superior mechanical properties, highlighting the substantial potential for industrial applications.