Effect of Y2O3 particles on the fracture toughness of directionally solidified TiAl-based alloys

The effect of Y2O3 particles on fracture toughness of directionally solidified (DS) TiAl-based alloys was studied. DS samples with various volume fractions of Y2O3 particles and similar lamellar structures were prepared by appropriate directional solidification and heat treatment. The typical microstructure of the samples consisted of α2/γ lamellae, a small amount of B2 phase and some Y2O3 particles, which were preferentially distributed in the local regions. The volume fractions of the Y2O3 particles ranged from 1.92% to 3.04%. The results of fracture toughness showed that an increase in Y2O3 particles would reduce the fracture toughness. The fracture phenomenology of cracking along ceramic particles, pulling out of Y2O3 particles and leaving smooth voids illustrated that Y2O3 particles had harmful effects on the fracture toughness of DS TiAl alloys.