A new glass-forming ability criterion for bulk metallic glasses

A new indicator of glass-forming ability (GFA) for bulk metallic glasses (BMGs) is proposed based on crystallization processes during cooling and reheating of the supercooled liquid. The interrelationship between this new parameter and the critical cooling rate or critical section thickness is elaborated and discussed in comparison with two other representatives, i.e. reduced glass transition temperature T-rg (= T-g/T-l, where T-g and T-l are the glass transition temperature and liquidus temperature, respectively) and supercooled liquid range DeltaT(xg) (= T-x-T-g, where T-x is the onset crystallization temperature and T-g the glass transition temperature). Our results have shown that DeltaT(xg) alone cannot infer relative GFA for BMGs while the new parameter gamma, defined as T-x/(T-g + T-l), has a much better interrelationship with GFA than T-rg. An approximation of the critical cooling rate and critical section thickness for glass formation in bulk metallic glasses is also formulated and evaluated. (C) 2002 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.