Study On Fabrication And Properties Of In Situ TiB₂/ZA27Composite

The Zn-Al based alloys have the potential to replace the traditional bronze and iron-base foundry alloys to produce wear resistant components due to their excellent tribological properties and lower melting temperatures. Recently, in situ fabrication technique has been developed. Since the formation and growth of reinforcement take place within the matrix, the in situ routes provide advantages including uniform distribution of particles, excellent bond at the interface, finer particle size, thermodynamically stable state of that overwhelm the conventional ex situ processes, yielding better mechanical and tribological properties.In this paper, the present work focuses on the fabrication, as-cast microstructure, mechanical and wear behavior of in situ TiB2particulate reinforced ZA27composite synthesized by the in situ mixed salt route. The resultant generated in situ TiB2particles are uniform fine, regular shape, and dispersed in the matrix. The microstructure of the matrix alloy has been significantly refined due to the addition of the in situ TiB2particles. The tensile strength and hardness of in situ TiB2/ZA27composite increase with the content of T1B2particle increasing, but the elongation reduces gradually. The tensile strength and hardness of5wt.%TiB2/ZA27composite was440MPa and129HB, respectively increased18.9%and21.7%compared with that of ZA27alloy. But the elongation was1.5%, declined46.7%compared with ZA27alloy. The fracture of in situ TiB2/ZA27composite is a typical brittle fracture with strengthening mechanism including fine grain strengthening, dispersion strengthening and dislocation strengthening.Compared to the ZA27alloy, the wear loss and friction coefficient of the in situ TiB2/ZA27composite significantly reduce. By SEM morphology analysis of the wear surface and subsurface, it can be seen that, the TiB2particle change the wear mechanism. The main wear mechanism of ZA27alloy is including of adhesive wear and abrasive wear. But the main wear mechanism of the in situ TiB2/ZA27composite is abrasive wear. The subsurface have stratified phenomenon. Compared with the ZA27alloy, the fine grain area of surface and layer flow area in the subsurface of in situ TiB2/ZA27composite are relatively thin, and with the increase of TiB2particle content the two areas both have thinning trend.