A novel method to enhance CSL fraction, tensile properties and work hardening in complex concentrated alloys ― Lattice distortion effect

A framework has been developed to reduce the stacking fault energy of complex concentrated alloys (CCAs) or high entropy alloys based on increasing lattice distortion by choosing principal elements with large differences in moduli and atomic size. The framework and selection criteria have resulted in the inclusion of five CCA compositions for validation of the lattice distortion and three Fe-containing CCAs. Orientation imaging microscopy (OIM) was used to examine the fraction of special boundaries in all of the CCAs. Alloys with large lattice distortion contained high density of annealing twins. Both tensile properties and work hardening rate characteristics were evaluated. CCAs that were designed based on lattice distortion demonstrated improved ultimate tensile strength. Work hardening rate curves revealed the underlying variation in the tensile properties of various CCAs. For selected alloys, post-deformation OIM analysis of the lateral surface was carried out for establishing defect density variation.