Strain hardening and substructural evolution in NiCo solid solutions at large strains

Abstract

Torsion deformation was used to investigate dislocation substructure evolution at large strains in high purity nickel and NiCo solid solutions. Observations of small strain dislocation structures formed in stage III revealed that the laminar dislocation structure observed after large strains in stage IV develops from short paired dislocation sheets within the tangled dislocations of an equiaxed cell wall. The development of these short paired dislocation sheets into long microbonds occurs gradually by a multiple-slip process in accordance with the principles of low energy dislocation structures and without the occurrence of a shear instability. The plane of these sheets and /or microbands does not correspond to a {111} slip plane. As these microbands form, a misorientation between the interior of the paired sheets and the surrounding matrix develops and increases with increasing strain.