A multi-scale study for detwinning in nanotwinned Ni-Cr and Ni-Fe alloys

Abstract Nanotwins (NTs) significantly enhance strength and thermal stability of face-centered cubic (FCC) alloys compared to coarse-grained counterparts. However, alloying elements can affect NT stability at elevated temperatures. We combined molecular dynamics (MD) simulations with a recently developed anisotropic multi-phase phase field model to investigate NT stability in two Ni-based binary alloys: Ni–Cr and Ni–Fe. MD simulations reveal Ni–Fe alloys have higher intrinsic stacking fault energies compared to Ni–Cr alloys across similar solute concentrations. Moreover, solute effects on incoherent twin boundary (ITB) energies differ notably. ITB mobility exhibits Arrhenius behavior within the studied temperature range. Phase field simulations, incorporating MD-derived mobility laws, demonstrate that NT/grain boundary detachment and subsequent detwinning strongly depend on annealing temperature and NT thickness, particularly above 0.4 homologous temperature. These insights aid in designing nanotwinned Ni-based alloys with improved thermal stability and mechanical properties; in particular, additional Cr or Fe content can significantly elevate the onset temperature of NT motion. Graphical abstract