Microstructure and Mechanical Properties of As‐Cast CoCrNi Medium‐Entropy Alloys Doped with Trace Amounts of Al and Ti

Microstructure and mechanical properties of the CoCrNi and (CoCrNi) 94 Al 3 Ti 3 medium‐entropy alloys are studied using X‐ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The results show that coaddition of Al and Ti not only reduces the grain size of CoCrNi medium‐entropy alloy, but also leads to a deviation (≈14.2°) of {100} texture. After a small amount of Al and Ti addition, the yield strength increases from 220 MPa in CoCrNi medium‐entropy alloy to 500 MPa in (CoCrNi) 94 Al 3 Ti 3 medium‐entropy alloy, and a three‐stage work‐hardening rate is observed. Grain refinement and solid solution strengthening are the primary contributors to the enhanced strength. Transmission electron microscopy characterization shows that numerous dislocations, abundant stacking faults, Lomer–Cottrell locks, and deformation twins are formed in CoCrNi medium‐entropy alloy after tension. The multiple deformation mechanisms result in an excellent ductility with an elongation of ≈76%. The dislocations, stacking faults, and Lomer–Cottrell locks can also be observed in (CoCrNi) 94 Al 3 Ti 3 medium‐entropy alloy after tension, while the deformation twinning is absent because of the grain refinement induced by Al and Ti addition. Notably, the observed heterogeneous dislocation distribution (regions of low and high dislocation densities) facilitates sustained work hardening throughout the process of plastic deformation.