Fabrication of spatially-variable heterostructured CoCrFeMnNi high entropy alloy by laser processing

This study investigates the fabrication of spatially-variable heterostructured CoCrFeMnNi high entropy alloy (HEA) using pulsed laser processing. Two distinct fabrication approaches, involving single-(SP) and double-sided (DP) laser passes, were employed. Microstructural characterization through electron backscatter diffraction revealed significant differences. SP-HEA exhibited a spatially heterogeneous microstructure with coarse columnar grains, while DP-HEA displayed a sandwich-like structure with fine equiaxed recrystallized grains. Microhardness mapping demonstrated a gradient trend in SP-HEA, with the fusion zone exhibiting the lowest hardness and the base material the highest. In contrast, DP-HEA displayed an overall soft-hard-soft structure. Tensile testing revealed distinct mechanical responses, with DP-HEA exhibiting higher strength and ductility compared to SP-HEA. The improved performance of DP-HEA was attributed to a more uniform distribution of heterogeneity, minimizing mechanical interactions between soft and hard domains. Moreover, corrosion resistance was assessed, showing that DP-HEA outperformed SP-HEA and non-processed material, suggesting superior stability in corrosive environments. These findings highlight the profound influence of fabrication parameters on the microstructure and mechanical properties of spatially-variable heterostructured HEAs. The study contributes valuable insights for material design and applications based on CoCrFeMnNi high entropy alloys.