Recrystallized hard zone and resultant tri-modal microstructure produces superior mechanical properties in a single-phase heterostructured high-entropy alloy

Heterostructured high-entropy alloys (HS-HEAs) integrate two innovative concepts in metallic materials that encompass alloy design and microstructural engineering. HS-HEAs have demonstrated outstanding mechanical properties. However, it remains challenging to explore these materials due to the intricate nature of their composition and microstructure. In this study, we introduced heterostructures into a single-phase FCC HEA through cold rolling and partial recrystallization. This process resulted in an exceptionally high density of nanoscale recrystallization twins, leading to significant hardening and the formation of heterogeneous hard zones in recrystallized regions with small grain sizes. This tri-modal heterostructure results in improved balance between strength and ductility, high zone boundary density and strong hetero-deformation induced (HDI) effects, and a unique two-stage strain partitioning mechanism that postpones necking. As a result, the alloy exhibits enhanced strength and ductility, resulting in superior mechanical properties. The identification of the recrystallized hard zones is crucial for gaining a proper understanding of the hetero-zones in HEAs and provides valuable insights for the future design of HS-HEAs.