Study On Fabrication And Properties Of Low Volume Fraction TiB_2P(+BN_P)/6061Al Composites

TiB2 particles reinforced 6061 aluminum matrix composites(Vf=14%,20%), TiB2 particles(Vf=14%)and h-BN particles(Vf=7%) hybrid reinforced 6061 aluminum matrix composites, were fabricated by pressure infiltration technique, then were extruded on the basis of optimizing hot extrusion process. The effects of reinforcement, heat treatment and hot extrusion on microstructure characteristics, tensile properties, friction and wear behaviors were studied by using of SEM, TEM, tensile testing machine, friction and wear tester.Results indicate that surface quality of composites extruded with the extrusion ratio of 10:1 is deeply related to the temperature of hot extrusion, The ideal surface quality of 14%TiB_2P/6061Al and 20%TiB_2P/6061Al composites was got at the hot extrusion temperature of 480℃, the composites are dense and reinforcement particles distribute uniformly after hot extrusion. The TiBB2-Al interface combined well, and there are slight reactants on the interface and some dislocations in the matrix alloy beside TiB2B particles caused by mismatch stress; sub grains are found after hot extrusion, and grain size are refined to 1³Î¼m, there are lots of fine precipitation in the size of 10³0nm dispersive in the matrix alloy.The tensile properties of 14%TiB_2P/6061Al, 20%TiB_2P/6061Al and 14% TiB_2P+7%BNP/6061Al composites increase after hot extrusion, The tensile strengths of them after hot extrusion in T6 state are 364.1MPa, 447.5MPa and 393.9MPa; with increases of 41.5%, 49.0% and 36.6% compare with unextruded composites respectively, the yield strengths and elastic modulus of them increase by 40.3% and 18.6% respectively at least. Particularly hot extrusion improved elongation ratios of 14%TiB_2P/6061Al and 20% TiBB2P/6061Al composites to 9.25% and 7.95% respectively. Fractographic analysis of composites indicates that hot extrusion increase the cohesion strength between reinforcements and matrix alloy.The friction coefficient of 14%TiB_2P/6061Al and 20%TiB_2P/6061Al are about 0.4 and 0.3, the main wear mechanism is adherence wear; the friction coefficient of 14%TiBB2P+7%BNP/6061Al is about or under 0.2, the friction surfaces show boundary lubricated wear property. The wear rate is around 10-¹³m³/(N·m); and has some relation to load, but not to sliding velocity.