Formation of ceramic/metallic glass composite by mechanical alloying

Recently discovered Zr-based bulk glass alloys can be produced by rapid quenching from the melt or as an alternative route by mechanical alloying. Here we present the formation of amorphous matrix-ceramic composite powders by mechanical alloying of an elemental powder mixture with the composition Zr65Al7.5Ni10Cu17.5 together with SiC particles. The effect of the added ceramic particles on glass formation and thermal stability was investigated with structural and thermal analysis. During the milling process an amorphous matrix with a homogeneous dispersion of SiC particles develops. This composite material reveals a glass transition followed by crystallization. The onset temperatures for these transformations are found to be increased by about 10 K in comparison the pure Zr-based alloy. This observation may be explained by small compositional changes in the amorphous matrix during the milling process. No indication for SiC dispersoids acting as heterogeneous nucleation sites was found. The kinetics of primary crystallization was found to be delayed. As such, mechanical alloying represents a useful method for preparation of amorphous-ceramic powders combining the improved mechanical properties of the amorphous state and particle dispersions.