We break the limit of grain refinement and strength of low-carbon steel by tuning deformation compatibility of heterostructure.

Piling-ups of geometrically necessary dislocation (GND) arrays against interfaces are known to produce hetero-deformation induced (HDI) strengthening and strain hardening to enhance the strength and ductility of heterostructured materials. Here we report an interesting dislocation mechanism that can produce strong HDI hardening: consecutive reflections of GND planar piling-up arrays near the opposite phase boundaries in a heterostructured AlCoCrFeNi₂ high entropy alloy (HEA). In contrast, dislocation transmission was found at grain boundaries in the fcc phase. The discovery here provides guidance for future materials design, which may improve the combination of strength and ductility of metallic materials. GRAPHICAL ABSTRACT IMPACT STATEMENT A hitherto unknown consecutive reflection of GND arrays near phase boundaries of a heterostructured HEA is observed and proposed as a key contributor to HDI hardening.

The chemical short-range orders (CSRO) are the sub-nanosized entities inherent in high-/medium-entropy alloys (H/MEA). To discern CSRO poses the challenge with pending issues as to under what zone axis in electron diffraction, signature scattering specific to CSRO will appear and what the structure motif of CSRO is. Here, we show extra diffuse scattering by CSRO from [111] and [112] directions in a VCoNi MEA and accordingly, construct the $\text{L}{1}_1$-type structure motif, and derive the spacial shape of flat cuboid of CSRO in virtue of diffractions under varying zone axis. Moreover, we demonstrate the methods to identify CSRO in lattice images. GRAPHICAL ABSTRACT IMPACT STATEMENT The structure motif is constructed as $\text{L}{1}_1$-type for chemical short-range order in a medium-entropy alloy in terms of electron diffractions under the multiple zone axis.