Microstructure, deformation and fracture characteristics of an Al67Ni8Ti25 intermetallic alloy

The microstructure and mechanical properties of Al₆₇Ni₈Ti₂₅ have been investigated. After homogenization, the microstructure consists primarily of large grains of the π phase with the L1₂ crystal structure, but second phase particles and pores are also present. The dislocation density in the π phase is low after homogenization. but increases substantially during compressive plastic deformation. In compression. Al₆₇Ni₈Ti₂₅ has a yield strength of 355 MPa at room temperature and can exhibit substantial plasticity. The mechanism of compressive plastic deformation is a₀〈110〉{111} slip. The a₀〈110〉{111} dislocations are not dissociated by more than 2 nm, indicative of high {111} APB and SISF energies. Under the influence of a tensile stress, Al₆₇Ni₈Ti₂₅is brittle and fails by transgranular cleavage. The brittle fracture behavior is consistent with ideas originally proposed by Rice and Thomson concerning an activation barrier for emission of dislocations from crack tips.