Rhombohedral Twinning in Alumina

Abstract

Alumina single crystals were deformed in compression along the c axes at T= 625 to 1373 K. Large‐scale deformation by rhombohedral twinning was observed at a constant resolved shear stress of only 12.6 MPa between ∼900 and 1373 K. Below 900 K, the twinning stress for specimens with ground surfaces rose rapidly to 227 MPa at 625 K. A model for twin growth in the absence of dislocation slip is proposed.