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.