Optimizing the microstructure and mechanical performance of Fe-Ni-Cr-Al high entropy alloys via Ti addition

The effect of Ti content on the microstructure and mechanical properties regulation for Fe45Ni30−xCr15Al10Tix high entropy alloys (HEAs) with a duplex FCC/BCC structure is investigated. The as-cast Fe45Ni30−xCr15Al10Tix HEAs have typical dendrite and inter-dendrite structure, where dendric and inter-dendric regions are FCC and BCC phases, respectively. After introducing Ti, the inter-dendric structure transforms into coexistence of disordered BCC and ordered B2/L21 phases. And the morphology of B2/L21 precipitates gradually changes from a regular maze-like mesh and cuboidal structure to elliptical structures due to the increase of the lattice mismatch. The change of precipitate type and volume fraction lead to that the ultimate tensile strength of the HEAs increases from 540 MPa to 1292 MPa. Meanwhile, it keeps the uniform elongation of 13.29%, showing outstanding strength-plasticity synergy.