Insight on the glass-forming ability of Al-Y-Ni-Ce bulk metallic glass

In the present study, the role of Ce in the thermal stability and glass forming ability (GFA) of (Al87Y8Ni5)99Ce1 alloy ribbons produced by a single roller melt-spinning process has been investigated in an attempt to understand the influences of multiple RE elements in an Al-TM-RE (TM: transition metal, RE: rear earth metal) alloy system. Only the (Al87Y8Ni5)99Ce1 alloy ribbon showed a glass transition temperature (Tg) at 483.2 K, and its ΔTx value was 41.3 K. Crystallization occurred in the temperature range of 500-750 K in three exothermic reaction stages. The peak temperature for these reactions shifted toward higher temperatures at higher heating rates. XRD and SEM analysis of annealed samples revealed that nano-sized Al particles precipitated within the amorphous matrix during the first exothermic reaction. The maximum hardness was obtained for both non-cerium and cerium addition alloys after crystallization in the 550-660 K region due to numerous nano-sized precipitates randomly and homogeneously distributed in the amorphous matrix. Moreover, from observation of the fracture surface, it is found that the fracture mode transforms from ductile to brittle when the sample is annealed at a higher crystallization temperature, at which brittle intermetallic compounds appear.