Bulk metallic glasses and composites in multicomponent systems

Single-phase (Zr/Ti)Cu-Al-Ni metallic glasses were synthesized by copper mo ld casting and mechanical alloying of elemental powder mixtures. In additio n. nanostructured metallic glass composites were produced by annealing of a s-cast specimens and by mechanical alloying of elemental powder mixtures bl ended with different volume fractions of ZrC particles. For cast specimens, the effect of composition on the thermal stability and the microstructure after partial crystallization was investigated by X-ray diffraction and dif ferential scanning calorimetry. Ti additions lead to a lower overall therma l stability of the material and induce primary crystallization. The grain s ize of the precipitates after the first crystallization stage becomes progr essively finer with increasing Ti content, yielding grain sizes as small as about 2 nm for Zr54.5Ti7.5Cu20Al10Ni8. For mechanically alloyed Zr55Cu30Al 10Ni5 powders containing up to 30 vol% nanoscale ZrC particles, stoichiomet ry variations of the glass due to particle dissolution in the glassy matrix during the mechanical alloying process were observed, which affect the the rmal stability of the glassy matrix phase. Nevertheless, the composites mai ntain an extended supercooled liquid region before crystallization.