Preparation and thermal stability of ceramic/metallic glass composites prepared by mechanical alloying

Abstract

We present the formation of ceramic/metallic glass composite powders by mechanical alloying of an elemental powder mixture with the composition Zr 65Al 7.5Ni 10Cu 17.5 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 distinct glass transition followed by crystallization. The onset temperatures for these transformations are found to be increased by about 10 K in comparison to the amorphous Zr-based alloy without SiC. 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. The microhardness of the ceramic/metallic glass composites was increased by about 25% compared to the value found for the single amorphous powder. As such, mechanical alloying represents a useful method for the preparation of ceramic/metallic glass composite powders combining the mechanical properties of the amorphous state and the ceramic particle dispersions.