Abstract
CoCrNi multicomponent alloys with equiatomic and non-equiatomic concentrations are promising for achieving an excellent balance of strength and ductility. However, the correlations between elemental concentrations and deformation mechanisms of this alloy family need to be uncovered for further targeted alloy design. In this work, atomistic molecular dynamics simulations were performed to study the effects of Co concentration on the mechanical behaviors and underlying deformation mechanisms of single-crystal Co-x(CrNi)(100-x) (x = 13, 23, 33.3, 50 at. %) alloys. Atomic-scale microstructural evolution with increasing the compressive strain was revealed in each specimen with different Co concentrations. The results suggest that the yield stress and elastic modulus are enhanced with increasing the Co content. Atomic pairs containing Cr exhibit the lowest cohesion energy among all pair types, and therefore Cr atoms participate most actively in dislocation nucleation. Although dislocation slip comes into play in all specimens, the primary deformation mechanism changes from the multilayering of stacking faults (SFs) to the formation of primary-secondary twin pairs with the increase of Co content. Further, the twinnability of these alloys was estimated using a theoretical model based on the generalized stacking fault energy (GSFE) curves. The results indicate that the Co50Cr25Ni25 alloy owns the highest twinning tendency among the probed alloy variants, which promotes the formation of secondary deformation twins and leads to high deformability. This work provides guidelines for the design of non-equiatomic CoCrNi multicomponent alloys with proper Co content for desirable mechanical properties.
NSTL
Elsevier