The Effect of Micron-Sized TiB2 Particles on the Properties of Al6061 Strengthened with 4% TiB2 Nano-TiB2

Abstract

Dual-scale (nano and micron) particle-reinforced TiB2/6061Al matrix composites with different contents of TiB2 were prepared using powder metallurgy, and then analyzed via microstructure observation and tests of microhardness, tensile properties, and friction and wear properties. The 6061Al powders’ particles changed from spherical to flaky after two rounds of high-energy ball milling, and the TiB2 enhancer was embedded in or wrapped by the matrix particles after high-energy ball milling. Metallurgical bonding between TiB2 particles and the matrix was achieved, and Al3Ti was synthesized in situ during sintering. The hot-pressing process eliminated the internal defects of the composites, and the TiB2 particles were diffusely distributed in the matrix. The best comprehensive mechanical properties (hardness and tensile strength) were achieved when the mass fraction of TiB2 was 5% (1% micron + 4% nano); the hardness and tensile strength of the composites reached 131 HV and 221 MPa—79.5% and 93.9% higher than those of the pure matrix, respectively. The composites’ average coefficient of friction and volumetric wear rate were reduced. Composites with a TiB2 mass fraction of 7% (3% micron + 4% nano) had the highest average coefficients of friction and the lowest volumetric wear rate of 0.402 and 0.216 mm3∙N−1∙m−1, respectively. It was observed that adhesion influences the friction mechanism, which transitions from adhesive wear with slight oxidative wear to abrasive wear.