Assessment of the thermodynamics, kinetics and crystallization sequence of Ni-Nb-P-based bulk metallic glass-forming alloys

Kurzfassung

This study investigates the glass-forming ability of Ni–Nb–P-based bulk metallic alloys through a systematic analysis of their thermodynamic, kinetic, and crystallization behavior. Differential scanning calorimetry, viscosity measurements, and in-situ synchrotron X-ray diffraction were employed to examine three compositions: Ni62Nb38, Ni59.2Nb38.8P2 and Ni59.2Nb33.8Ta5P2. While all alloys exhibit a high thermodynamic driving force for crystallization, the phosphorus- and tantalum-containing variants demonstrate significantly improved glass-forming ability. This improvement is linked to increased viscosity and suppression of primary crystallization. In particular, the addition of phosphorus promotes the formation of a phosphorus-rich intermetallic phase that requires long-range diffusion, delaying crystallization. The combined kinetic slowdown and delayed phase formation sufficiently retard crystallization, allowing fully amorphous samples up to 6 mm in diameter to be produced, compared to 2 mm for binary Ni–Nb. These findings highlight how judicious micro-alloying can enhance glass-forming ability through kinetic control of the crystallization pathway.