INVESTIGATION ON THE SOLIDIFICATION MICROSTRUCTURE, MICROSEGREGATION AND MECHANICAL PROPERTIES OF CF/AL 4.5Cu METAL MATRIX COMPOSITES

The solidification processing of metal matrix composites has a strong influence on their mechanical properties. In the present work, the effects of solidification cooling rate on the solidification microstructure, microsegregation and mechanical properties of CF/Al-4.5Cu metal matrix composites were investigated experimentally. The results showed that during the solidification processing of squeeze casting CF/Al-4.5Cu composites, α-Al phase nucleated first in the interstice regions of CF, but eutectic θ-Al₂Cu phase nucleated and grew on the surface of CF. As the solidification cooling rate decreased, crystallized quantity of θ-Al₂Cu phase also decreased; its shape was changed from large block-like to particle-like; meantime, the microsegregation of Cuelement also decreased, but the bent strength of the composites increased. Besides, because the fiber-metal interface was strongly bonded in the CF/Al-4.5Cu composites, the fracture surface of the composites showed the characters of brittle fracture, and no fiber pull-out was observed in any of these composites.