Elastic stresses and slip intersections with f.c.c. twins

Abstract

When slip takes place in f.c.c. metals containing annealing twins, slip may be reflected from a twin boundary, or it may be parallel to the twin boundary in the matrix and the twin, or it may pass continuously from matrix to twin to matrix. Finite element method (FEM) calculations permitted a determination of the matrix-twin orientation where each type of behavior would take place. Experiments were carried out on 70–30 α-brass bicrystals, tri-crystals and multi-crystals to check the calculations. Experiments were found to agree with calculations. When reflecting slip occured adjacent to a pile-up in a twin, it was possible to determine the identity of the reflecting slip system from FEM calculations and from a determination of the stresses resulting from the pile-up on the ( 11 1 ) [101] T slip system. It was also possible to identify the slip systems in the matrix, slip systems which operated as a result of the pile-up. For orientations in which slip would be reflected from a twin boundary calculations revealed that stress distributions were not the same for thick and thin twin cases, a situation which would produce transmission of slip across the thin twin but not the thick twin.