A conceptual approach to evaluate glass-forming ability for various glass-forming systems has been proposed from a physical metallurgy point of view. It was found that the glass-forming ability for noncrystalline materials was related mainly to two factors, i.e., 1/(Tg + Tl) and Tx (wherein Tx is the onset crystallization temperature, T g the glass transition temperature, and Tl the liquidus temperature), and could be predicated by a unified parameter γ defined as Tx/(Tg +Tl). This approach was confirmed and validated by experimental data in various glass-forming systems including oxide glasses, cryoprotectants, and metallic glasses.

Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability.

The mechanical behavior of bulk metallic glasses (BMGs) was investigated by nanoindentation with a spherical indenter. The transition from perfectly elastic behavior to plastic deformation was clearly observed as a pop-in event (sudden displacement excursion) on the load-displacement curves. Hertzian stress analysis was used to describe fully the load-displacement behavior during elastic deformation and to determine the theoretical shear strengths of the BMGs.

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 Trg ( =Tg /Tl, where Tg and Tl are the glass transition temperature and liquidus temperature, respectively) and supercooled liquid range △Txg ( =Tx-Tg, where Tx is the onset crystallization temperature and Tg the glass transition temperature). Our results have shown that △Txg alone cannot infer relative GFA for BMGs while the new parameter g, defined as Tx/ (Tg +Tl), has a much better interrelationship with GFA than Trg. An approximation of the critical cooling rate and critical section thickness for glass formation in bulk metallic glasses is also formulated and evaluated. 2002 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.

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 Trg ( =Tg /Tl, where Tg and Tl are the glass transition temperature and liquidus temperature, respectively) and supercooled liquid range △Txg ( =Tx-Tg, where Tx is the onset crystallization temperature and Tg the glass transition temperature). Our results have shown that △Txg alone cannot infer relative GFA for BMGs while the new parameter g, defined as Tx/ (Tg +Tl), has a much better interrelationship with GFA than Trg. An approximation of the critical cooling rate and critical section thickness for glass formation in bulk metallic glasses is also formulated and evaluated. 2002 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.