Strong-to-fragile transition in a metallic-glass forming supercooled liquid associated with a liquid-liquid transition

Liquid-liquid transitions are present in a variety of substances. However, investigating the liquid-liquid transitions occurring in a supercooled liquid is difficult because of the interference from rapid crystallization. Here, we report a strong-to-fragile transition in a Pd32Ni52P16 metallic glass-forming supercooled liquid associated with a liquid-liquid transition. Since the liquid-liquid transition takes place at temperatures smaller than the crystallization temperature, the liquid viscosity can be acquired by creep experiments conducted at temperatures close to the glass transition temperature without interference from crystallization. The strong-to-fragile transition results in a 37% increase of the fragility index and a 56% elongation after thermal-plastic processing. An investigation on the loss-modulus peaks by a dynamic mechanical analyzer implies that the enhanced thermal plasticity is contributed by both glass transition and strong-to-fragile transition. This work highlights how liquid-liquid transition affects liquid fragility and how it may aid the thermal-plastic processing of metallic glass.