Influence of Casting Parameters on the Critical Casting Size of Bulk Metallic Glass

The effect of various casting parameters and thermophysical properties of bulk metallic glasses (BMGs) on critical section size, defined as the maximum casting size that generates a through-section amorphous alloy, has been analyzed using a simple heat-transfer model. It was found that the interfacial heat transfer between the mold and the casting has a strong influence on the critical section thickness of a BMG. It is argued herein that the critical cooling rate rather than the critical casting size is a more robust indicator of glass-forming ability (GFA). Further, with respect to the critical cooling rate and heat-transfer effects during casting, a distinct difference was found between the critical casting thickness in rectangular-shaped castings and the critical casting diameter in rod-shaped castings, and a relationship was derived for relating these parameters.