Microstructure, mechanical property and wear behavior of AlCrFe1.5Ni1.5 medium entropy alloy

In present study, a cost-effective Co-free AlCrFe1.5Ni1.5 medium entropy alloys (MEAs) have been developed by vacuum melting technology. The microstructure of the AlCrFe1.5Ni1.5 MEAs and mechanical characteristics as well as wear behavior were explored in detail. The XRD patterns indicate that the crystal structure of AlCrFe1.5Ni1.5 MEAs includes dual phases of ordered B2 phase and disordered BCC type [Fe, Cr] phase. The lamellar dendritic regions and a spinodal decomposed microstructure can be observed from the microstructural morphology. The TEM analysis of nano structural evolution further identified the formation of Al-Ni-rich B2 phase and Cr-Fe-rich BCC phase with a high degree of coherence. Attributed to the spinodal decomposition of BCC phases, the as-cast AlCrFe1.5Ni1.5 alloy shows the exceptional plasticity (plastic strain > 40 %) and fairly high yield strength of 1231.64 MPa and fracture strength of 2172.79 MPa at room temperature. The true strength was 1360.88 MPa, accompanied with a high true strain of 35.44%. Besides, it also shows great work hardening ability and desirable mechanical properties at elevated temperature. The detailed investigation on the wear behavior shows low average friction coefficient and wear volume loss during the dry sliding process. The wear mechanism involves the abrasive and adhesive wear as well as oxidation. As a result, the dual phase strengthening in AlCrFe1.5Ni1.5 MEAs contributes to the excellent mechanical properties and wear resistance.