Atomic force microscopy of twin formation in low-stacking fault CuAl alloy

CuAl single crystals of a low stacking fault energy have been deformed along the [111] direction in an apparatus which consists of a compression machine interfaced with an atomic force microscope. The emergence process of dislocations has been in situ studied during deformation. Plasticity occurs in this material by propagation of Shockley dislocations which generate two possible kinds of stacking faults, extrinsic or intrinsic. The fine structure of slip lines has been investigated by atomic force microscopy. A differentiation between these two possible twin mechanisms in this alloy is attempted. It is concluded that twinning in this material can not only be explained by the intrinsic stacking faults and that the contribution of extrinsic faults has to be considered.