Nucleation of twinning dislocation loops in fcc metals

Deformation twinning, which occurs in fcc metals only under particular conditions of intrinsic material properties, microstructure, and loading conditions, occupies an indispensable place in their deformation mechanism maps. Nonetheless, dedicated studies have seldom been carried out to explore the fundamental properties of twinning dislocations mediating this process. Here we employ a combination of atomistic computations and continuum modeling to investigate the nucleation of twinning dislocation loops in metals with fcc crystal structure. Besides the conventional layer-by-layer model of twin nucleation, the newly proposed alternate-shear mechanism has been investigated, and the energy barrier and shear stress for twinning loop nucleation have been determined. We find the nucleation stress in the latter mechanism to be smaller than that in the former. The study also highlights the non-uniform variations of the critical loop size and fractional Burgers vector with the applied shear load.

Automated summary

This study investigates the nucleation of twinning dislocation loops in metals with fcc crystal structure using a combination of atomistic computations and continuum modeling. It explores both the conventional layer-by-layer model and the newly proposed alternate-shear mechanism for twin nucleation, finding differences in nucleation stress between the two mechanisms. The research also highlights the non-uniform variations in critical loop size and fractional Burgers vector with applied shear load.