2000 Volume 64 Issue 4 Pages 250-256
Directional solidification experiments were conducted for polyvinylidene fluoride (PVDF) or copper fiber reinforced pure succinonitrile (SCN) or SCN-2.2 mass% acetone alloy composites in order to investigate the effect of fibers on dendrite growth of matrix alloys. The relative distance (ΔL) (i.e., the length between the dendrite tip in the fiber-reinforced region (composites) and that in the unreinforced region (bulk) along the heat flow direction) varies according to fiber species and growth rate. In PVDF fiber reinforced pure SCN specimens, ΔL increases as the inter-fiber spacing decreases. The difference of thermal diffusivity between matrix and fibers should change the cooling rate of the matrix among the fibers. ΔL increases more in PVDF fiber reinforced SCN-2.2 mass% acetone alloy composites than in pure SCN specimens. Furthermore, the curvature of dendrite tips and the growth rate of the secondary dendrite arm in the composites decrease because the fibers restrain the solute diffusion and enrich the solute around dendrites. ΔL decreases with increasing gap between the fiber and glass because the heat flow and solute transport may become faster through the gap and the apparent thermal and solutal diffusivity approach those in bulk material.
