In situ stir cast Al–TiB₂ composite: processing and mechanical properties

Abstract

Elemental Ti and B powders of stoichiometric composition were mixed and added to molten aluminium. In situ TiB₂ particles were formed in the aluminium melt. On casting, an Al–TiB₂ composite was produced. Despite the presence of the Al₃Ti phase associated with the Al–Ti–B ternary system, the in situ TiB₂ particles, with sizes of 1–3 µm formed in the composite was able to yield an improvement of 57% increase in tensile strength, 66% in yield strength and 22% in modulus in an Al–15 vol.-%TiB₂ composite. The extent of improvement in these properties depended on the volume fraction in the composite. Fractography showed a texture of dimples seated with hexagonal TiB₂ particles indicating retention of high ductility in the composite, despite the fact that the predominance of the coarse Al₃Ti in the composite had led to premature rupturing.