| Own to it’s excellent wear resistance, hypereutectic Al-Si alloy is widely used in the production of wear resistant parts. At present, high-silicon aluminum alloy liner is mainly produced by the spray deposition technology. The German PEAK company and Daimler-Benz company has used the spray deposition technology to make hypereutectic Al-Si alloy liner, and it has successful application in automobile V6 engine. Compared with cast iron cylinder liners, the aluminum-silicon alloy prepared by spray deposition method has lighter weight, lower wear rate, less fuel consumption and tail gas emission. But the spray deposition technology also has the disadvantages of complex process, high cost, low production efficiency and so on. These problems limit the application and popularization of high-silicon aluminum alloy.The traditional casting method has the advantages of simple process, high production efficiency and low cost. The coarse microstrucure of the hypereutectic Al-Si alloy made by traditional casting process severely cuts off the metal matrix, so the performance of Al-Si alloy is greatly deteriorated. Fe in cast hypereutectic Al-Si alloy has a dual nature: on the one hand, the addition of Fe in cast hypereutectic Al-Si alloy can form coarse iron-rich phase, so the mechanical property of the alloy is reduced; on the other hand, compared with the matrix, the iron-rich phase not only has higher hardness, but also has high temperature stability. So it is favorable for the wear resistance, especially high temperature wear performance of the alloy. Therefore, in this paper, Fe as an alloying element will be applied to the preparation of Al-Si alloy. In this paper, the influence of Fe content on the fluidity of the hypereutectic Al-Si alloy has been studied by using the Al-P modifier on the primary silicon; The effect of Fe content on microstructure and phase composition of hypereutectic Al-Si alloy has been discussed; The refinement effect of heat treatment and Mn modification on thick iron-rich phase in hypereutectic Al-Si-Fe alloy has been analyzed and the best mass ratio of Mn and Fe was given; The influence of temperature and load on dry sliding wear properties of new hypereutectic Al-Si alloy and the matrix alloy has been investigated, and their friction and wear mechanism has been explored in order to lay the research foundation for the realization of producing aluminum-silicon alloy liner with the traditional casting.Through the research of this paper, the following conclusions are drawn:(1) Fe is harmful for the casting property of hypereutectic Al-Si alloy, and the fluidity of the hypereutectic Al-Si alloy decreases with the increase of Fe content. With the increase of Fe content from 1wt.% to 5wt.%, the flow length of Al-Si alloy decreases from 1241 mm to 350 mm. When the Fe content is 5wt.%, the flow length is reduced by 73% compared with that without Fe. Therefore, it is necessary to control the content of Fe in order to reduce the damage to the casting property of the hypereutectic Al-Si alloy. In this paper, the content of Fe in the new hypereutectic Al-Si alloy is 2wt.%.(2) Fe added to the hypereutectic Al-Si alloy has formed needle shaped iron-rich phase. And with the increase of the Fe content, the coarse structure in the alloy is more and more. XRD and EDS show that the iron-rich phase in the alloy is mainly the β-Al5 FeSi phase. The long needle Fe-rich phase has negative effect on the mechanical properties of the alloy, so it is necesarry to refine the iron-rich phase.(3) Iron-rich phase has high temperature stability, so it can not be refined by heat treatment. After adding proper amount of modifying elements Mn in the alloy, morphology of thick iron-rich phase has been greatly changed, relieving the separation of the matrix by long needle-like iron-rich phase to a certain extent. The experiments show that the best Mn/Fe mass ratio is around 1:1.(4) The dry sliding wear experiments show that the hypereutectic Al-Si alloy has better anti-adhesive wear performance under high temperature. Below the critical temperature, the wear rate of the alloy is very small. Once surpassing the critical temperature, the wear rate of the alloy increases dramatically. Experiments shows that the new hypereutectic Al-Si alloy has higher critical transition temperature than that of the substrate alloy; under the same load, sliding speed and temperature, the wear resistance of the new hypereutectic Al-Si alloy is higher.(5) The sliding wear mechanism of the alloy mainly includes abrasive wear, adhesive wear, oxidation wear, delamination wear, thermal softening wear and fatigue wear. Under low temperature and low load, wear mechanism is mainly abrasive wear and slight adhesive wear. Under high temperature and high load, delamination wear, thermal softening wear and fatigue wear are the main wear mechanism. |
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