Microstructure and compression properties of a dual-phase FeCoCrMn high-entropy alloy

Both the dual-phase and multi-phase high-entropy alloys show excellent mechanical properties. The dual-phase FeCoCrMn alloy consisted of alternating lamellar face-centered-cubic (FCC) and sigma (σ) phases was developed in this work. The FCC and σ phase were identified to be FeCoMn-rich and Cr-rich phase, respectively. The alloy showed high compression yield strength of 1431 MPa at room temperature, which was attributed to the specific lamellar structure and high volume fraction σ phase (46%). The ductility was limited (compression strain was about 1%), due mainly to the inherent brittleness of σ phase. The compression properties at elevated temperatures were also evaluated. The yield strength and compression strain at 400 °C were 758 MPa and 12.6%, respectively. The yield strength at 800 °C was 181 MPa. The strengthening mechanisms of the alloy at different temperatures were discussed based on the microstructural characterization. The improved thermal activation process and the strength decline of both the FCC and σ phases at the elevated temperatures may be responsible for the decreased yield strength and increased ductility. In addition, the comparison of yield strength between FeCoCrMn alloy and other high-entropy alloys was also made.