Fabrication And Mechanical Properties Of （TiB₂+Al₂O₃）/2024Al Composites With A Quasi-continuous Network Distribution

Conventional aluminum matrix composites are usually fabricated with ahomogeneous distribution of reinforcements in the matrix. This structure does notdisplay the best ductility because the integrity of the matrix is compromised. Tosolve this problem, a new structural material with a network distribution wasdesigned and prepared.2024Al,TiO₂and B powders were mixed using low energyball milling. Then network composites were in-situ fabricated by vacuum hotpressing technique. The microstructure and morphology of composites along withthe change rule of B/TiO₂were discussed using XRD、SEM and TEM. WhenB/TiO₂was2,4/3,0， mechanical properties of the as-sintered and extrudedcomposites were measured. Effects of the change rule of B/TiO₂on mechanicalproperties of composites were systematically investigated..To network structured composites, effects of the ball milling parameters on themorphology of the raw materials were discussed.150rpm and2h proved to be theoptimum ball milling parameters. The reaction temperature was determined as810℃using DTA. The optimum holding time was established as60minutes afterstudying the effects of holding time on the morphology of the reinforcements.When B/TiO₂was2,4/3,0,（TiB₂+Al₂O₃）,（TiB₂+Al₂O₃+Al₃Ti） and （Al₂O₃+Al₃Ti） were produced. Fine TiB₂and Al₂O₃particulates both with a size of about0.5m，bulky Al₃Ti with a size of about25m were observed using TEM and SEM.Reinforcement scattered along the boundary of the2024Al effectively strengthenedthe2024Al matrix. Also, the interpenetrating nature of the matrix contributed to theductility of the composite.Results of the mechanical properties at room temperature indicates that theproperties of the sintered and extruded composites are enhanced with the increasingpercentage of B. The mechanical properties of the composite with B/TiO₂as2aresuperior to the other two systems. The room temperature tensile strength andelongation of the as-sintered composites of this system are294MPa and3.77%.With subsequent hot extrusion of this composite, the mechanical properties wereenhanced to370MPa and6.5%. Mechanical properties at high temperature indicatesthat the tensile strength of composites is reduced and the elongation is improved.Compared experimental results revealed that the mechanical properties of thecomposites where B/TiO₂is2are superior.