Microstructure And Properties Of TiB / ZL205A Composites

Aluminum matrix composites with low density, high specific strength, high specific modulus, good thermal and electrical conductivity and other advantages, are widely used in the automotive industry, aerospace, integrated circuits, and so on. But the traditional meathod prepared reinforced aluminum matrix composite material is prone to having pores, inclusions and other defects. The wettability between the reinforcement and the substrate is bad, and its interface binding is not strong.These conditions have serious effects on the mechanical properties of materials.TiB2 particles reinforced ZL205A composites were prepared by mixed salt reaction method in this paper. Effect of preparation technology parameters (reaction temperature, stirring speed and reaction time) on the composite particles (shape, size and space) were studied; the fluidity factors (casting the temperature, composition and the content of TiB2 particles) of composite materials were analysed; mechanical properties, microstructure, fracture mechanism and strengthening mechanism of the composite materials were deeply studied.The fluidity, microstructure, fracture morphology, phase composition and mechanical properties of aluminum matrix composites were characterized with the help of a single helix alloy fluidity tester, optical microscope, scanning electron microscope, X ray diffraction, electronic universal testing machine and other testing instrument. The results were obtained as follows:(1) The optimum process parameters of aluminum matrix composite prepared by mixed salt reaction method are the reaction temperature at 900 ℃, stirring speed at 400rpm and reaction time at 50min. The in situ synthesis TiB2 particle with the size of around 1 um, the type of hexagonal or oval, homogeneous distribution in the matrix and the good combination with substrate interface have been obtained through the optimization preparation process;(2)The liquidity(168 mm,710℃) of the composites increased with the increasing of pouring temperature, is poorer than that of ZL205A(251 mm,710℃) and AlSil2 (360 mm,710℃), and decreased with the increasing of TiB2 content;(3) The tensile strength, yield strength and elastic modulus of aluminum matrix composites with heat treatment are 464.4 MPa,416.1 Mpa,87.3GPa, respectively, compared with that of ZL205A alloy increased by 49.8%,113.4%,24.4%. The elongation is 1.9%, compared with that of alloy decreased by 72.1%. The heat treatment has no effect on the ZL205A matrix alloy and composites;(4) The in situ formation of TiB2 particles in the matrix alloy has changed the fracture mechanism of material from transgranular ductile fracture to cleavage fracture (the main) and transgranular ductile fracture (the auxiliary). Particle rein-forced aluminium based composite material enhanced mechanism is a hybrid rein-forcement theory (including grain refinement strengthening, dispersion strengthening and dislocation strengthening theory).