Synthesis of in situ Al-TiB2 composites using stir cast route

Abstract

When elemental Ti and B powders were added to molten Al at above 1000°C, fine in situ TiB2 particulates were formed through Al-Ti-B exothermic reaction. By optimising the nucleation of TiB2, the tensile and yield strengths of a synthesised Al-15V(f)%TiB(s) composite were twice that of matrix material. Modification of Al-matrix with 4.5 wt%Cu tripled the tensile and yield strengths at peak-aged condition. Owing to the co-presence of brittle Al3Ti flakes with TiB2 particles in the composites synthesised by the Al-Ti-B system, ductility was reduced to 68% and 84% in composites with Al- and Al-Cu matrices, respectively. When the (Ti + B) mixture was incorporated with 3 wt%C, TiB2 and TiC reinforcing phases were simultaneously produced in the composite with Al-Cu matrix. Such an approach reduced Al3Ti compound in the composite considerably. Although the presence of Cu in the composite was found to promote the formation of Al3Ti, its effect on the fluidity caused the melt recovery to increase from 33% to 52%. (C) 2000 Elsevier Science Ltd. All rights reserved.