Compositional landscape for glass formation in metal alloys

Area of Science:

• Materials Science
• Thermodynamics
• Crystallization Kinetics

Background:

• Understanding glass-forming ability (GFA) is crucial for developing bulk metallic glasses.
• The Ni-Cr-Nb-P-B system is a promising candidate for metallic glass formation.

Purpose of the Study:

• To experimentally determine a high-resolution compositional map of GFA in the Ni-Cr-Nb-P-B system.
• To elucidate the relationship between composition, crystallization pathways, and GFA.

Main Methods:

• Experimental determination of GFA across various compositional planes.
• Analysis of compositional dependence of GFA and its correlation with nucleation pathways.

Main Results:

• GFA is a piecewise continuous function with intersecting subsurfaces linked to specific crystalline phase nucleation.
• Exponential variations and cusps in GFA were observed at transitions between crystallization pathways.
• Peak GFA occurs at interconnected 'hypercusps', enabling the formation of >1 cm glassy rods.

Conclusions:

• The GFA landscape arises from the interplay of crystallization thermodynamics and kinetics (thermodynamics vs. liquid fragility).
• Specific compositions are critical for achieving high GFA and forming bulk metallic glasses.