COLUMNAR-TO-EQUIAXED TRANSITION IN METAL-MATRIX COMPOSITES REINFORCED WITH SILICON CARBIDE PARTICLES

ALICIA E. ARES; CARLOS E. SCHVEZOV

Journal of Metallurgy

Hindawi Corporation

Lugar: New York; Año: 2013 vol. 2013 p. 1 - 12

1687-9465

The present work is focused on the study of the effect of directional heat extraction on the  Silicon-Carbide (SiC)  distribution in  zinc-aluminum matrix composites  (MMCs)  and on the columnar-to-equiaxed (CET) position in directionally solidified samples. To this end, a ZA-27 alloy matrix was  reinforced with ceramic particles  of SiC  and  vertically directionally solidified.   The cooling rates, temperature gradients,  and interphase velocities  were  then  measured,  and  their  influence on the solidification microstructure of the MMCs  was  analyzed.  The recalescence detected and measured during the equiaxed transition  was  of  the order of 3.5°C to 1.1°C. The values of the temperature gradients reached  a minimum during the CET  and were  even negative  in most cases  (between  -3.89 K  and  0.06 K).  The interphase velocities  varied  between 0.07 mm/s and 0.44 mm/s at the transition. Also, the presence of ceramic particles in ZA27 alloys affected the thermodynamic local conditions and the kinetics of nucleation, producing a finer microstructure.