Using the Cu-Zr model system, we demonstrate that bulk amorphous alloys can be obtained by copper mold casting even in a binary metallic system. The narrow, off-eutectic, bulk-glass-forming range was found to require composition pinpointing to Ͻ1 at. %. A phase selection diagram is used to explain the success of our microstructure-based approach to pinpoint the best glass former in a given system. The implications of discovering simple binary bulk amorphous alloys are discussed, in terms of its impact on understanding the formation and physics of bulk metallic glasses.

Homogeneous nucleation kinetics for melting in superheated crystals is analyzed in order to derive a kinetic stability limit for the crystal lattice above its equilibrium melting point ͑T m ͒. It is found that at a critical temperature (T K m , which is about 1.2T m for various elemental metals) a massive homogeneous nucleation of melting occurs in the superheated crystal. Such a homogeneous nucleation catastrophe, which occurs before other proposed (rigidity, volume, and entropy) catastrophes can intervene, provides us with a kinetic stability limit for superheated crystals. [S0031-9007(98)06099-2]

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