Synergetic strengthening and deformation mechanisms in gradient Al_0.1CoCrFeNi high-entropy alloy

A gradient-structured (GS) Al_0.1CoCrFeNi high-entropy alloy, introduced by simple torsional methodology, achieves a good combination of strength and ductility. Specifically, the yield tensile strength of the T-GS sample almost three times the annealed sample, and meanwhile, it exhibits an ultimate tensile strength with gigapascal level while retaining an acceptable homogeneous elongation. Synergetic strengthening from GS effect yields a unique up-turn behavior close to elastoplastic region in strain-hardening-rate response, indicating the onset of additional strengthening, i.e., accumulations of geometric necessary dislocations. This feature is well accordance with nanoindentation hardness measurements that definitely display visible gradient distribution from center to edge of GS samples, and theoretical predictions further confirm the synergetic strengthening effect that consists of grain-boundary strengthening (grain refinement) and deformation-substructures strengthening (dislocations and nanotwins).