Influence of interfaces on the plastic deformation in Ti-Al

The alloy Ti-48.6Al-1.9Cr-1.9Nb-1B with a near gamma microstructure, obtained by heat treatment at 1200 degrees C for 4 h, and with a lamellar microstructure, obtained by heat treatment at 1380 degrees C for 1 h, is characterized by compression tests and transmission electron microscopy. A lower activity of superdislocations and a more frequent pinning of ordinary dislocations are detected in the lamellar Ti-A1 specimens in comparison with the non-lamellar ones during deformation at room temperature. The lower activity of superdislocations and the more frequent pinning of ordinary dislocations is responsible for the higher yield stress in lamellar Ti-A1 compared with non-lamellar Ti-A1. The different deformation mechanism in the lamellar structure is explained by the effect of the lamellar interfaces, which can transform superdislocations into ordinary dislocations, and where a very high density of locked ordinary interfacial dislocations has been found. The lamellar interfaces influence the activity of superdislocations and the pinning of ordinary dislocations and modify the mechanical properties. (C) 1998 Elsevier Science S.A.