Bulk Nanostructured Multicomponent Alloys

Bulk nanostructured composite materials can be obtained by partial devitrification of slowly cooled bulk glass-forming multicomponent metallic glasses or by blending a glassy matrix alloy with insoluble second-phase particles by solid state processing. Their properties are discussed with respect to the effect of the second phases on the thermal stability and on the mechanical properties at room temperature as well as at temperatures around the glass-transition temperature, Tg. Microhardness measurements at room temperature reveal a substantial increase in the hardness of the composites because of the uniform distribution of nanoscale particles in the glassy matrix. Also, there is a significant increase in yield strength with increasing volume fraction of particles. At elevated temperatures around Tg volume fractions of up to 40 vol.-% of nanoscaled particles yield no significant change in strength as compared with the particle-free material, but the deformation behavior of the composites is mainly controlled by the Newtonian viscous flow of the glassy matrix phase. This easy-flow behavior opens a promising route for shaping complex parts of bulk nanostructured composites derived from metallic glasses at moderate temperatures and high strain rates.