Refined microstructure and enhanced mechanical properties of AlCrFe2Ni2 medium entropy alloy produced via laser remelting

A Co-free as-cast AlCrFe2Ni2 medium entropy alloy (MEA) with multi-phases was remelted by fiber laser in this study. The effect of laser remelting on the microstructure, phase distribution and mechanical prop-erties was investigated by characterizing the as-cast and the remelted AlCrFe2Ni2 alloy. The laser remelt-ing process resulted in a significant decrease of grain size from about 780 mu m to 58.89 mu m (longitudinal section) and 15.87 mu m (transverse section) and an increase of hardness from 4.72 +/- 0.293 GPa to 6.40 +/- 0.147 GPa (longitudinal section) and 7.55 +/- 0.360 GPa (transverse section). It was also found that the long side plate-like microstructure composed of FCC phase, ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases. The mechanical properties were evaluated by the derived stress-strain relationship obtained from nano-indentation tests data. The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa (longitudinal section) and 1647.2 MPa (transverse section) after remelting. The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated, including grain boundary strengthening, dislocation strengthening, solid solution strengthening and precipitation strengthening. The calculation results indi-cated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.