Mechanisms of the electron irradiation-induced amorphous transition in intermetallic compounds

A buildup of radiation-induced lattice defects is proposed as the cause for lattice instability that can give rise to a crystalline-to-amorphous transition. An analysis of published experiments on intermetallic compounds suggests that, when amorphization takes place, no microstructural evolution based on the aggregation of like-point defects occurs. This observation leads us to suggest that buildup of a different type of defect, which will destabilize the crystal, should occur. We thus propose that an interstitial and a vacancy may form a complex, giving rise to a relaxed configuration exhibiting a sort of short-range order. Two mechanisms of complex formation are analyzed, one diffusionless (limited by the point defect production rate) and the other temperature dependent. The amorphization kinetics as a function of temperature, dose, and point defect sink strength are studied. Theoretical predictions on the amorphization dose as a function of temperature are made for the equiatomic TiNi alloy and compared with available experimental results.