Research On Surface Microcrystallization Of Aluminum Alloy Of Tire Mould By Added-pressure Shot Peening

In recent years, Nano-crystalline structure of Al alloy had been attained through the surface nano-crystalline technology, since it has a series of excellent mechanical and physical and chemical properties [1-2], were preliminary used in the field of rubber molds productionBut, the surface nano-crystalline was applied to 7050 Al alloy tire mould, it was difficult for making the technology industrialization, because 7050 Al alloy tire die-cavity roughing strength is not very high, wallop of alloy surface grain which was refined up nanoscale was too big, it can break tendons and arris of mold and damage mold cavity. Therefore, this paper proposed a kind of shot peening micro-crystalline (grain size closed to about 100nm), and analyzed the influence of micro-crystalline the process of tyre moulds on the surface, which was exerted by process parameters of projectile diameter and shot peening time, microcrystalline layers of wear resistance, corrosion resistance, electrochemical performance of sulfide and the influence law were researched. the special properties of the micro-crystalline materials was hoped to improve the performance of tyre moulds. The main research contents of paper were as follows:1. Through the experiment the optimization of process parameters of surface micro-crystalline 7050 A1 alloy had realized, including shot peening pressure, shot peening time, projectile diameter, etc. micro-crystalline layer of hardness and wear performance were determined.2. The thermal stability of microcrystalline layer was studied. Experiment results indicated that activation energy of grain growth on micro-particlization treatment of the surface of aluminum alloy were more 16.1 kJ/mol than untreated samples. Namely, the treated samples possess relatively exceptional thermal stability.The results of mircohardness as well as XRD analysis meet agreement with DSC curves, therefore, micro-crystalline layer heat stable temperature of 7050 aluminum alloy surface was about 200℃. 3. tyres production work condition was simulated by plate vulcanizing experimental, compared with sulfide pollution resistant performance between the original and as-prepared samples. Two plate sulfur vulcanization experiments were carried out, which respectively focused on the consideration of duration and cycles of sulfur vulcanization. Both of the two experiments'results show that the treated sample owned better antifouling performance than the original which can attribute to the cooperation of the treated surface with low reaction properties, and the cooperative binary structures at micro-meter scales which reduce the energies of the surfaces for one thing and for another thing reduce the adhering areas for the fouling.4. Electrochemical corrosion performance of surface microcrystalline Al alloy samples in corrosive medium of 3.5% NaCl solution has improved to varying degrees, the corrosion potential of as-prepared samples has improved, the corrosion current also correspondingly reduced. This showed grain refinement of aluminum alloy surface was more likely to form a layer of oxide layer and the other was because of existing refinement microcrystalline organization was formed tiny and densify film in natural conditions of oxide, so as to effective protect metal substrate, which made oxidation process slowing. The corrosion resistance was enhanced.