Fundamental aspects of bulk metallic glass formation in multicomponent alloys

During the past several years, a number of multicomponent alloy families have been investigated in which the liquid alloys form metallic glass at cooling rates below 1000 K/s and as low as 1 K/s or less. These ''bulk'' metallic glass forming alloys have been cast from the melt into glass samples with the smallest dimension ranging from millimeters to centimeters. The undercooled liquid alloys show remarkable resistance to crystallization permitting studies of thermal and physical properties, the glass transition, and crystallization behavior of the melt over previously inaccessible temperatures in the deeply undercooled region. One group of these alloys, which includes the Zr-Ti-Ni-Cu-Be and Zr-Ti-Ni-Cu systems, has been extensively investigated in our laboratory. Results of atomic diffusion and viscosity measurements, crystallization behavior and TTT-diagrams, and studies of liquid phase separation in the deeply undercooled liquid have been carried out and will be discussed. Engineering properties and potential applications of these bulk glasses will be briefly mentioned. (orig.)