Gradient structured high-entropy alloy with high hardness and corrosion resistance after laser shock peening

Abstract

In the effort to improve the surface properties of FeCoCrNiMn HEA, gradient structure was prepared by laser shock peening (LSP), a versatile and efficient method to achieve distinct surface properties. The underlying mechanism of the LSP strengthening effect was discussed based on microstructure analysis, mechanical properties, and corrosion test. Our results suggested that ultra-fined grains and high density of defects were produced after LSP treatment which accounts for the significant enhancement of hardness, coefficient of friction (CoF), and corrosion resistance. The strengthened mechanical properties owed to the large amount of grain boundaries and high density of defects that significantly attenuate the movement of dislocations. Meanwhile, attributed to the compressive residual stress induced by LSP, the penetration of corrosive solution was effectively impeded and the passivation process was accelerated. Finally, the different mechanisms of LSP strengthening effect have been discussed. This study presented a promising approach to address the challenge of surface modification of FeCoCrNiMn HEA and provided a novel strategy for regulating the microstructure of HEA and achieving outstanding properties.