Microstructure formation mechanism and corrosion behavior of FeCrCuTiV two-phase high entropy alloy prepared by different processes

Highlights: • FeCrCuTiV HEA prepared by vacuum arc melting and LMD both form FCC+BCC soild solution structure. • Grain size and Cu-rich (FCC) phase volume fraction of HEA prepared by LMD is smaller. • HEA prepared by LMD shows better corrosion resistance due to the reduction of Cu-rich segregation phase. The microstructure and corrosion resistance of FeCrCuTiV high entropy alloy prepared by vacuum arc melting and laser melting deposition were studied. The microstructure and phase composition of FeCrCuTiV high entropy alloy were characterized by SEM, XRD, EBSD, etc. It is found that both of them are composed of the FCC Cu-rich phase, BCC Fe-rich phase and, BCC V-rich phase. Comparing with FeCrCuTiV high entropy alloy prepared by vacuum arc melting, the grain size of FeCrCuTiV high entropy alloy prepared by the laser melting deposition reduces from 29.48 µm to 1.85 µm. Meanwhile, the Cu-rich phase volume fraction decreases from 44.7 % to 31.5 %. Two reasons contribute to this phenomenon: On the one hand, the higher cooling rate of high entropy alloy makes the grain growth limited and the grain size reduced. On the other hand, the higher cooling rate reduces the volume fraction of intergranular segregation Cu-rich phase formed under non-uniform solidification due to the lack of long-range migration of Cu element, which makes the solidification state of FeCrCuTiV high entropy alloy prepared by laser melting deposition deviate from the ideal thermodynamic equilibrium. In addition, the corrosion resistance test of FeCrCuTiV high entropy alloy prepared by two processes indicates: FeCrCuTiV high entropy alloy prepared by laser melting deposition shows better corrosion resistance under the electrochemical corrosion of salt solution. This result is caused by the reduction of the Cu-rich phase, which weakens its corrosion effect as the anode of galvanic cell. Laser melting deposition technology provides new ideas and methods for controlling the phase structure of complex solid solution high entropy alloys to improve their physical properties.