Deformation structure during creep deformation in soft orientation PST crystals

Deformation microstructure of soft polysynthetically twinned (PST) crystals Ti-48A1 was investigated. The soft orientation with the lamellar plates or iented 35 degrees to compression axis was deformed at 1150 K under applied stresses of 100-251 MPa. Macroscopically anisotropic deformation was observ ed after creep deformation. Deformation took place in the maximum shear str ess direction in the soft orientation. Dislocation structures in domains of six different variants were examined by transmission electron microscopy. Operative slip and twinning systems were also analysed. Macroscopic plastic strain and strain compatibility at domain and lamellar boundaries were dis cussed in terms of the slip systems in each domain. Refinement of lamellar occurred by mechanical twinning during creep deformation. (C) 2001 Elsevier Science Ltd. All rights reserved.