The interaction between slip and twinning systems and the influence of twinning on the mechanical behavior of fcc metals and alloys

Abstract

The analysis of twin-slip and twin-twin interactions in fcc crystals is reviewed using the method proposed by Sleeswyk and Verbraak for the interactions between bcc twins. Slip or twinning dislocations impinging a twin boundary can generally be incorporated into the obstacle twin through often unfavorable dislocation reactions. Transmission electron microscopy observations are in agreement with the predicted mechanisms of stress relaxation. The link with Bollmann’s concepts for more general boundaries as applied to these simple Σ = 3 boundaries is emphasized. However the limitations of such analyses are pointed out particularly their inability to predict the influence of stress conditions. From the analysis and observations of interactions at twin boundaries the influence of twinning on work-hardening and fracture in fcc metals and alloys is tentatively outlined. In particular twinning can give rise to an increase of the flow stress particularly in polycrystals and it is actually responsible of the high mechanical properties of a number of commercial compositions. Experimental evidences of the role of twinning in the fast fracture and the fatigue fracture of fcc materials are reported which are in agreement with the inferences made from the study of various interactions.