Structural change of deformation twin boundaries in a heavily deformed gamma-TiAl-based alloy

Structural change of deformation twin boundaries in gamma phase of a Ti-45A l-10Nb-2.5Mn alloy with similar to 29% deformation strain has been investig ated by TEM. We found numerous bent twins propagating in the gamma matrix, which were inclined at angles of a few degrees to the (111)(M) plane in the gamma matrix. HREM observations showed that (111)(DT) plane in the twins e xhibited a large misorientation angle with the (111)(M) plane, and many 1/3 [111] Frank partial dislocations were observed in the incoherent twin bound aries. These 1/3[111] Frank partials, which were possible to form through d issociations of matrix dislocations at the twin boundaries, can accommodate the bending of the twins and the misorientation from the true-twin orienta tion relationship. (C) 2000 Elsevier Science B.V. All rights reserved.