Stuydy On Phase Diagram, Phase Transformation And Properties Of High Aluminum Zn-Based Alloys

High Aluminum Zn-based alloys are simple at smelting technics and have excellent mechanical properties, foundry properties, machining properties and especial wearable properties. Furthermore, the sources of raw material are wide, the cost is lower and it is not be contaminative. Due to all of these advantages, this type of alloy has quickly grown up in domestic and overseas as a new kind of alloy. However, investigation of high Aluminum Zn-based alloys has not form a perfect system owing to the develop time is not enough. In this thesis, firstly, we reinvestigated binary Al-Zn phase diagram system by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and pushrod dilatometer (PRD). Secondly, we analysed metallographic structure of Zn-Al alloy and tested high temperature impact properties of ZA27 Alloy. Lastly, we compared the microstructure and wear-friction properties of high Aluminum Zn-based alloys at some different heat treatments.The results show that:(1) There are one peritectic reaction, one eutectic reaction and one eutectoid reaction in the phase diagram of the Al-Zn binary system, them are:Peritectic reaction: L(14%A1)+ α (30%Al) →|(443℃) (29%A1)Eutectic reaction: L(5.1%Al)→|(382℃)(17.2%A1)+ n(l%Al)Eutectoid reaction: β (22%A1) → |(275℃) α₁(68.4%Al)+ η(0.6%Al)(2) Typical dendritic structure of the as-cast ZA27 consists of four phases α , β , εand η The core of the dendrite is α phase Al rich, which is surrounded by the decomposed Zn-rich β phase, located in the interdendritic region are eutectoid (α + η.) and ε . The structure of ZA27 is hard particles distributed in soft matrix. The as-cast unequilibrium eutectic structure can be uniform by solution treatment.(3) The impact fracture morphology mostly is tear ridges and dimples. Higher the impact energy, more obvious the character of tear ridges. Dimples are small and distribute more uniformity. Lower the impact energy, the less distinct the tear ridges. Dimples are larger and deeper, their distributing are asymmetrical.(4) High Aluminum Zn-based alloys carry through annealing treatments in different temperatures after them are dealt with solution treatment. With increasing of isothermal temperature, α dendrite become coarse and the lamellar constituents become coarse of granule, even hardness is gradually decrease.(5) High Aluminum Zn-based alloys, especially the ZA30 alloy can obtain lower friction coefficient and the best wear-friction properties at the first heat treatment (360℃ /8h quenching and 100℃/6h artificial aging).(6) After treate'd with three different heat treatments, the wear-friction mechanism of Al-containing Zn-based alloys is transform from furrow to furrow and tired peel by the increasing of annealing temperature. And the adhesive-wear is raised with the increase of Al content.(7) Through the test that ZA30 treated with 360℃/8h quenching and 100℃/6h artificial aging has set in machine a long time, shows that this alloy can replace the ZQSn6-6-3 alloy.Guangxi is abundant in non-ferrous mineral resources, especially in Zinc and Aluminuml. So the present work is significant for the exploitation and utilization of resources as well as the development of economy in Guangxi.