Fracture behavior of directionally solidified NiAl-Mo and NiAl-V eutectics

A rod eutectic, Ni-45.45at.%Al-9at.%Mo, and a lamellar eutectic, Ni-30at.%Al-40at.%V, were directionally solidified by the containerless electromagnetically levitated zone (CELZ) process. Four-point bend tests were used to determine the fracture toughness of the CELZ processed eutectic alloys, while scanning electron microscopy and transmission eletron microscopy of tested samples were used to characterize the fracture behavior. The composite structures of these alloys provide improvement in fracture toughness over binary NiAl primarily by crack bridging and trapping for NiAl-9at.%Mo, and crack bridging and renucleation for NiAl-40at.%V. Significant plastic deformation of the NiAl phase prior to fracture also contributes to the toughness of both eutectic systems.