Diffraction from single and overlapping stacking faults in F.C.C. crystals

Single intrinsic stacking faults in f.c.c. crystals are observed to give rise to diffraction spots in h.c.p. positions and anomalous diffraction spots in twin positions. This, together with similar observations in diffraction patterns from overlapping faults, are discussed in relation to the problem of determining the extent to which overlapping faults generated by plastic deformation constitute nuclei of h.c.p. or twinned material. The results suggest that nuclei of twin or h.c.p. material develop by the filling in of a disordered array of faults rather than by the operation of polar mechanisms.