PREPARATION AND THERMAL-STABILITY OF CERAMIC METALLIC GLASS COMPOSITES PREPARED BY MECHANICAL ALLOYING/

We present the formation of ceramic/metallic glass composite powders b y mechanical alloying of an elemental powder mixture with the composit ion 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 parti cles develops. This composite material reveals a distinct glass transi tion followed by crystallization. The onset temperatures for these tra nsformations are found to be increased by about 10 K in comparison to the amorphous Zr-based alloy without SiC. This observation may be expl ained by small compositional changes in the amorphous matrix during th e milling process. No indication for SiC dispersoids acting as heterog eneous nucleation sites was found. The kinetics of primary crystalliza tion was found to be delayed. The microhardness of the ceramic/metalli c glass composites was increased by about 25% compared to the value fo und for the single amorphous powder. As such, mechanical alloying repr esents a useful method for the preparation of ceramic/metallic glass c omposite powders combining the mechanical properties of the amorphous state and the ceramic particle dispersions. (C) 1998 Elsevier Science B.V. All rights reserved.