EVIDENCE OF SHEAR LIGAMENT TOUGHENING IN TIAL-BASE ALLOYS

Shear ligament toughening is a process by which fracture resistance of a material is enhanced as the result of the redundant deformation and shear fracture of intact ligaments that are formed In the crack wake. A recent micromechanical model has suggested that shear ligament toughening is responsible for the resistance-curve fracture behavior observed in lamellar TiAl-base alloys. In this article, various aspects of the shear ligament-toughening mechanism are evaluated by performing critical experiments. Experimental evidence supporting the presence of shear ligament toughening in TiAl-base alloys is presented together with st quantitative comparison of the proposed model against experimental data. Both the experimental results and model calculations indicate that the resistance-curve fracture behavior in lamellar TiAl-base alloys is indeed a manifestation of shear ligament toughening.