Study On The Microstructure And Properties Of In-situ TiB₂Particles Reinforced Zn-Al Alloy By Spray Deposition Process

Zinc-aluminum alloys with excellent mechanical and tribological properties have been used to process bearings, bushings and other wear-resistant components to replace copper and aluminum alloys. The resources of zinc is abundant, while the copper resource is deficient in China. Based on the rich resources, the research and development of zinc-aluminum alloy will have a significant economic benefits, and promote social development.The TiB2/Zn-30Al-1Cu composite was prepared by a combination of way of in situ reaction and spray deposition.Thermodynamic calculations were used to determine the thermodynamic stability of each component in the Al-Ti-B reaction system. The microstructure of TiB2/Zn-30Al-1Cu composite was studied by OM, SEM, TEM, XRD, DSC. The properties of the composite were evaluated by hardness measurement, tensile testing, friction and wear testing.There were mainly Al (1)+2B=AlB2(s), Ti+3Al (1)=Al3Ti (s), Ti+2B=TiB2(s) present in the Al-Ti-B reaction system. It was found that TiB2had the lowest Gibbs free energy by thermodynamic calculation and it was the most stable under thermodynamic conditions. In the melt, AlB2and Al3Ti would transfer to TiB2through AlB2(s)+Al3Ti (s)=TiB2(s)+4Al(1).The microstructure of spray deposited TiB2/Zn-30Al-1Cu composite was consists of primary a’ phase, lamellar, cellular, granular a+η structure, and nearly spherical TiB2particles, while the low melting point eutectic phase was disappeared. Some black precipitates(η-Zn) exsited in a’ phase, which indicated that the a’ phase would transfer to a+η structure.After solution treatment at360℃, it was found that the grain of Zn-30Al-1Cu alloy began to grow after10minutes, while the grain of TiB2/Zn-30Al-1Cu would not grow until20h later. The mechanical properties and hardness of TiB2/Zn-30Al-1Cu were higher than those of Zn-30Al-1Cu before and after solution treatment due to the presence of TiB2particles.The tensile strength of TiB2/Zn-30Al-1Cu composites could reach to450MPa, its elongation was21.5%and it had excellent mechanical properties.The friction and wear properties of TiB2/Zn-30Al-1Cu were slightly lower than those of bronze, but superior than those of the Babbits.