Effects of Ti and Al additions on microstructure and mechanical properties of FeCrNi medium entropy alloy fabricated by laser powder bed fusion

Microstructure and mechanical properties of Ti and Al containing FeCrNi medium entropy alloy (MEA) were investigated. FeCrNi and (FeCrNi)94Ti3Al3 MEAs were successfully fabricated using laser powder bed fusion. The addition of Ti and Al changes the phase formation and tensile properties of FeCrNi MEA. With the addition of alloying elements Ti and Al, the structure of FeCrNi MEA changed from single FCC structure to FCC + BCC dual-phase structure. Furthermore, the dual-phase structure resulted in a significant enhancement in both the yield strength and strain hardening rate. The high yield strength (~ 948 MPa) and ultimate tensile strength (1421 MPa) of as-built (FeCrNi)94Ti3Al3 MEA was attributed to the combined effect of strengthening mechanisms including solid solution strengthening, grain boundary strengthening, dislocation strengthening, and back stress strengthening. The criteria for phase formation in the FeCrNi-based MEAs were discussed. This work provided a new insight for high-mechanical properties and low-cost dual-phase additive manufactured high-entropy alloys for nuclear applications.