Construction of biphasic FeCrAlWx high entropy alloys coating of BCC and Al-rich FCC second phase for dual enhancement of strength and plasticity

In this work, a series of novel FeCrAlWx (x = 0.25, 0.5, 0.75, 1) high entropy alloys (HEAs) coating were successfully prepared using laser cladding technology to simultaneously enhance both strength and plasticity. The effect of W on the microstructure, phase composition, strength, and plasticity of the coating was investigated. The results showed that the FeCrAlW0.75 HEAs coating, which exhibits a biphase structure consisting of a bodycentered cubic (BCC) phase and a nanoscale Al-rich face-centered cubic (FCC) second phase, displays the most favorable overall performance. Specifically, FeCrAlW0.75 HEAs coating demonstrated a hardness, ultimate tensile strength, and ultimate elongation of 750.9 HV, 875.6 MPa, and 36.6 %, respectively, highlighting the simultaneous enhancement of strength and plasticity. The enhancement of strength in biphase FeCrAlW0.75 HEAs coating was attributed to the hardness of the BCC phase increased via added W, while the improvement in plasticity can be attributed to the twinning structure and low slip resistance of the nanoscale Al-rich FCC second phase. Furthermore, we analyzed the mechanism of W-improved strength by first-principles calculations, and investigated the formation mechanism of the nanoscale Al-rich FCC second phase for W-induced utilizing a pseudo-binary approach based on phase diagrams and elemental characteristics.