Twin-slip, twin-twin and slip-twin interactions in Co-8 wt.% Fe alloy single crystals

Abstract

The crystallographic features of twin-slip, twin-twin and slip-twin interactions in crystals, deformed in plane-strain compression in the [11̄0] (110) orientation, have been examined using optical metallography. It is observed that the matrix slip can propagate across the existing twin boundaries. The slip traces evolved during the propagation appear to satisfy the geometrical requirement that the slip planes in the matrix and twin intersect along a line which lies in the coherent twin boundary. The dislocation reactions have been proposed to explain the evolution of the observed features. Generally the twin intersections are accomplished by secondary twinning in the crossed twin, but accommodation of the strain of the crossing twin by slip in the crossed twin has also been observed. The line of intersection of the habit planes of the crossing and secondary twins lie in the composition plane of the crossed twin. Arguments for rationalizing these observations have been developed. The deflections produced in the existing slip traces by propagating twins have been evaluated. The agreement between the observed and computed values is satisfactory. Mechanisms of incorporating the existing slip dislocations into propagating twins are also considered.