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Research on High Aluminum Zinc-Based Alloy Tyre Valves

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Tutor: WangJiZuo SunJing
School: Shandong University of Science and Technology
Course: Mechanical Manufacturing and Automation
Keywords: Tyre valve body,high aluminum zinc-based alloy,mechanical property,micro-structu
CLC: U463.341
Type: Master's thesis
Year:  2011
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Tyre valves are important constituent elements and have wide market requirements in industry production. Until recently, H70 and HPb59-1 brass have been the main bodies of valves. However, the soaring price of copper brings great pressure on valve industry. Therefore, it is a burning problem to search a kind of very strong substitute which has lower cost. Zinc and aluminum resources are abundant in our country, and high aluminum zinc-based alloy has good performance to replace copper. So the paper proposes the high aluminum zinc-based alloy replacing copper to produce tyre valves.Based on reviews of development and the status quo of the research on high aluminum zinc-based alloy, this kind of new material which has good performance at normal temperature and strong creep resistance at high temperature via adding reinforcement such as zirconium and ceramics into matrix alloy. Metallurgical structure, mechanical property and enhancement mechanism of ZA42 alloy are studied and compared with HPb59-1 brass and ZA27 alloy. The results show that the alloy¡¯s mechanical properties at room temperature and high temperature are all improved. Its room-temperature proof strength reaches to 521.8MPa which is 1.71 times than that of ZA27 and is 14% higher than that of brass; When it is heated to 120 degrees, ZA42 alloy¡¯s proof strength reaches to 230MPa which is 1.53 times than that of ZA27 and is a little higher than that of HPb59-1. Therefore, ZA42 alloy can completely replace HPb59-1 under room temperature and 120 degrees.The micro-structure, fracture mechanism and enhancement mechanism of ZA42 alloy are analyzed in this paper. The study shows that the structure of ZA42 high aluminum zinc-based alloy contains allitic¦Áphase, Zn-rich¦Âphase, Cu-rich¦Åphase and a few Zr-rich phase. Under room temperature and high temperature, the fracture modes of ZA42 are transgranular fracture and intergranular fracture respectively. Dislocation effects and the formation and growing up of ¡¯micro hole¡¯ are the ain fracture mechanisms. Composite dispersion hardening of hard phase particles such as Zirconium and alumina ceramic is the main strengthening mechanism of ZA42.Through friction and wear experiments, the frictional and wear properties of high aluminum zinc-based alloy ZA42 and HPb59-1 brass are compared in this paper. The result shows that, under the conditions of dry friction at room temperature and the temperature of 120 degrees, frictional and wear property of ZA42 alloy is better than that of HPb59-1 brass.Tyre valve bodies of high aluminum zinc-based alloy ZA42 are prepared by adopting molding technique of copper valves. The successful preparation proves that high aluminum zinc-based alloy ZA42 can completely substitute for brass to produce inflating valve bodies.
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