SLIP AND TWINNING IN TIAL PST CRYSTALS

Deformation structures were examined in Ti52Al48 PST single crystals o rientated for in-plane shear (soft orientation). It was found that all twins are ordinary twins. No super-twins were observed. It was also f ound that out-of-plane deformation (slip and twinning) plays an import ant role in the deformation of these samples. Furthermore, the critica l resolved shear stress for ordinary slip is slightly lower than that for ordinary twinning in our crystals. Since a combination of in-plane ordinary twinning and in-plane ordinary dislocation slip cannot produ ce compatible strains in all domains of a given layer in the PST struc ture, we suspect that the out-of-plane strains are necessary to reliev e the incompatibilities which are not relieved by in-plane super-dislo cations. (C) 1997 Elsevier Science S.A.