Study On Stability And Service Behaviors Of Deformation Zn-Al-Ti Alloy

The research in this thesis is supported by the project in the National Science&Technology Pillar Program during the Eleventh Five-Year Plan Period (2009BAE71B00) for the theme of replacing copper with zinc. The stability of deformation Zn-Al-Ti alloys represented by ZAT10alloy for structural parts was studied. Microstructures, mechanical properties, and service performances of ZAT10alloy were analyzed and compared comprehensively, so as to analyse the phase transformation during use, ascertain the main factors and creep mechanism affecting the dimensional stability of the alloy, and establish a suitable heat treatment process to improve the size and performances stability of ZAT10alloy. Furthermore, service behaviors of test alloys were researched, which served in different conditions, such as tensile load, bending load, strain rate, temperature, and medium. So that the significant effects of the heat treatment process mentioned on the dimensional and performance stability can be validated.The results show that a better stabilizing heat treatment process for high strength deformation Zn-Al-Ti alloy is preferably kept at350℃for30min with furnace cooling, then kept at120℃for1Oh, which improves the efficiency by2-3times than the traditional stabilizing heat treatment. The eutectoid transition (β→α+η) occurred during the heat treatment and the desolventizing decomposition of aluminum-rich a-phase refine the microstructures of experimental alloys, which is mainly, composed of uniform lamellar, granular and cellular α+ηstructure.In addition, the stabilization heat treatment obviously improves the creep resistance of high strength deformation Zn-Al-Ti alloys served under constant tensile and bending loads. The creep mechanisms of experimental alloys may be dislocation glide mechanism, dislocation climb mechanism and vacancy aggregation-empty connection mechanism at room temperature.ZAT10alloy tested in tap water and3.5%NaCl does not have SCC susceptibility. The deformation resistance and the maximum load strength increases during SSRT test, while its plasticity reducsd after stabilization heat treatment.Morever, aluminum-rich a-phase in deformation Zn-Al-Ti alloys is the corrosive phase. The process of corrosion of test alloys is an electrochemical corrosion process, which dissolved with the η phase as cathode, and Al element as anode.