MICROSTRUCTURE OF A380-SIC(P), COMPOSITES FOR DIE-CASTING

The distribution of silicon carbide (SIC) particulate in the matrix of an A380-SiC(p) composite of a die-cast chain wheel depends upon the s ize of the SiC particulate, the core pin materials and the plunger vel ocity during the die-casting process. SiC particulate (13 mu m) is dis tributed homogeneously in the die-cast product and the particulate con tent remains the same after the casting process. However, the 60 mu m SiC particulate causes particulate segregation and settling in the sho t biscuit and does not pass easily through a gate of 1.0 mm thickness. Further, it reduces the particulate content in the die-cast product a nd causes inhomogeneous particulate distribution in the teeth of the c hain wheel. Using SIGH 4A steel as a core pin, the SiC particulate was distributed very uniformly around the screw bolt holes of the product . In contrast, SiC-free zones were observed around the screw bolt hole s when using sintered tungsten carbide (WC) as a core pin. A faster pl unger velocity of 3.8 m s(-1) or a slower velocity of 0.3 m s(-1) resu lt in some SiC-free zones in the cast product. (C) 1998 Elsevier Scien ce S.A. All rights reserved.