Effects of Ti addition on structural evolution and tensile properties of Co-free CrFeNi multi-principle element alloys

The microstructure and mechanical properties of Ti-x(CrFeNi)(100-x) multi-principle element alloys (MPEAs) (x = 0, 1, 2, and 4) were systematically investigated. A heterogeneous microstructure containing grains and precipitates was formed in this alloy system as x increased from 1 to 2; further, the yield strength and ultimate tensile strength were improved significantly from 316 MPa to 766 MPa and 684 MPa to 1095 MPa, respectively, without significant loss in the plasticity, which is correlated to the strengthening effect of the co-existing several methods of hardening. The Ti-4(CrFeNi)(96) alloy with a heterogeneous microstructure of precipitates exhibited a higher yield strength (exceeding 1 GPa) and maintained approximately 12% ductility, which is related to the existence of fine grains and L1(2) fine precipitates. This work provides a valuable design strategy to achieve a good combination of high strength and good ductility in MPEAs via simple composition adjustment.

Automated summary

The microstructure and mechanical properties of Ti-x(CrFeNi)(100-x) multi-principle element alloys were systematically investigated. The addition of CrFeNi resulted in a heterogeneous microstructure containing grains and precipitates, leading to significantly improved yield strength and ultimate tensile strength. The Ti-4(CrFeNi)(96) alloy exhibited a high yield strength and good ductility, attributed to the existence of fine grains and L1(2) fine precipitates.