Influences of laser surface melting on microstructure, mechanical properties and corrosion resistance of dual-phase Cr–Fe–Co–Ni–Al high entropy alloys

In this paper, a laser surface melting (LSM) method was utilized on CrFeCoNiAl_x (x = 0.5, 0.6, 0.7) high entropy alloys (HEAs) with FCC + BCC structure, and the effects of LSM on their microstructure, mechanical properties and corrosion behavior were systematically investigated. It is intriguing that, a layer with BCC + B2 structure formed on the surface of CrFeCoNiAl_0.6 and CrFeCoNiAl_0.7 substrates after LSM, while a monolithic FCC layer formed on that of CrFeCoNiAl_0.5 substrate under the same condition. LSM influences the mechanical properties of CrFeCoNiAl_x HEAs to varying degrees including hardness and tensile properties decided by the phase formation in laser-treated surfaces and the substrates. In addition, compared to the substrates, obvious increase in self-corrosion potential and pitting potential were found in the laser-treated surface layers of CrFeCoNiAl_0.6 and CrFeCoNiAl_0.7. Interestingly, the corrosion resistance of laser-treated surface layers has positive correlation with Al content, while that of the substrates shows negative correlation with the concentration of Al, which is possibly resulted from the difference in corrosion mechanism. This work provides a new route for significantly improving surface properties of dual-phase HEAs, which would be very beneficial to their further application as advanced materials.