Basal slip in sapphire (alpha-Al2O3)

Plastic deformation of sapphire has been performed along three different compression axes to activate (0001) basal slip along one or two [<(11)over bar>20] directions. One of the orientations is identical to that used in earlier experiments, with the activation of one glide direction, or Burgers vector. We also investigated two new orientations which permit activation of two Burgers vectors. We oa have shown that for one of these orientations, rhombohedral twinning is difficult to activate and large deformations, for unpolished specimens, can be reached by basal slip down to 900 degrees C. Basal glide along [01 (1) over bar 0] was observed; the yield stress values are the same for [01 (1) over bar 0] and [0 (1) over bar 10] directions. (C) 1997 Elsevier Science S.A.