Effect of Si and P on the Formation and Crystallization of Ti_(25)Hf_(50)Ni_(25) Metallic Glasses

摘要

Ti_(25)Hf_(50)Ni_(25) metallic glasses, prepared by rapid quenching, are strongly metastable with a 65℃ separation between the glass transition temperature, T_g = 335℃, and the onset temperature for primary crystallization. The deep metastability of the glass is likely due to sluggish nucleation and growth kinetics, limited by the Hf diffusion. The glass crystallizes to a nano-scale microstructure consisting of an icosahedrally symmetric ordered phase. This phase is metastable and transforms to a stable Ti_2Ni-type phase with annealing at higher temperatures. The primary crystallization to a metastable icosahedrally-ordered phase suggests that the local structure of the glass contains a high degree of icosahedral short-range order. Here, glass formation and crystallization were studied in alloys containing 2 at.% of Si and P.