Phase stability and mechanical properties of an ultra-fine grain FeCoNiCu0.4Al0.4 high entropy alloy

FeCoNiCu0.4Al0.4 high entropy alloy (HEA) were produced via mechanically alloyed (MA) and spark plasma sintering (SPS) at 950~1100 °C. Microstructure and mechanical properties of bulk HEA are studied. In the sintering process at temperatures ≤1050 °C, disordered FCC phase precipitates BCC phase. When sintering temperature increases to 1100 °C, only single FCC phase could be clearly detected. The stability of FCC phase is obviously influenced by the sintering temperature, therefore strength-ductility balance could be tailored by controlling BCC/FCC ratio via changing sintering temperature. The FeCoNiCu0.4Al0.4 alloy sintered at 1050 °C obtains a combination of excellent strength (yield strength=1562.4 MPa) and good plasticity (plastic strain to failure=30.3 %) at room temperature. The reason for the excellent strength of this HEA is mainly because the grain boundary strengthening in FCC matrix.