Characterisation of mechanically alloyed Ti–Al–B nanocomposite consolidated by spark plasma sintering

Abstract

Abstract The microstructure and mechanical properties of TiB2/Al nanocomposites based on the Ti-Al-B system, consolidated by spark plasma sintering of mechanically alloyed activated nanopowders, have been characterised. Mechanical alloying was carried out in a planetary ball mill for 120-180 min at 350 rev min-1. The powders were pressed in vacuum at a pressure of 60 MPa; a dc current of 1800 A was applied for 4 min, generating a maximum temperature in the graphite mould of 1400° C. Analysis of the synthesised nanocomposites by SEM, XRD, and TEM showed them to consist of TiB2 second phase particles, 10-30 nm in size, in a near amorphous Al phase, with unreacted Ti and B on grain boundaries as a ternary phase. Composites consolidated from powders mechanically alloyed from an initial elemental powder mix of 0·3 mol Al, 0·7 mol Ti, and 2·0 mol B achieved the best relative density (98%) and bending strength (847 MPa); the highest Vickers hardness of 19·6 GPa was achieved for the 0·1:0·9:2·0 mol starting composition.