| With the rapid development of automobile industry, the automotive lightweighting also developed rapidly, which results in the lightweight aluminum alloy composite used widely. Al/Fe bimetal composite combines of the advantages of aluminum alloy with lightweight and good corrosion resistance and cast iron or steel with high strength and good wear resistance, so it is able to meet the performance requirements from different parts of the automobile parts and has a broad application prospect in automotive material field. In order to meet the demands of wear resistance, heat conductivity and strength of aluminum alloy automobile engine cylinder, and control the cost of production at the same time, Al/Fe bimetal composite casting technology was developed to fabricate Al/Fe bimetal composite cylinder body. This research focuses on achieving metallurgical bonding at the interface between aluminum alloys and iron or steel and guaranteeing the interface bond quality at a lower production cost.In order to study the effect of different composite casting process on Al/Fe bimetal composite, we have analyzed and compared the specimens obtained by directly pouring, hot dipping+pouring, and fluxing+hot dipping+pouring, respectively. The results show that the interface of the specimens obtained by directly pouring has an obvious gap, so it just is mechanical bonding. The bonding interface of the specimens obtained by hot dip aluminizing before pouring forms a continuous intermediate phase layer (consisting of Al5Fe2 and Al8Fe2Si phases), so it achieves metallurgical bonding. Meanwhile, fluxing treatment can improve the quality of metallurgical bonding. In addition, we have tested the coefficient of thermal conductivity of the specimens obtained by different process, and the result showed that metallurgical bonding can greatly improve the thermal conductive property of the Al/Fe bimetal composite. When the thickness of the metallurgical bonding layer is about 10μm, its coefficient of thermal conductivity is highest and is about 10 times higher than the coefficient of thermal conductivity of mechanical bonding.To explore the effect of Mn on the Al/Fe interface, this paper studies the interface microstructure of the specimen obtained by hot dipping aluminum alloy melt containing 1-5wt% Mn before pouring. Through analysis of interface morphology and composition, we found that the addition of Mn in dipping bath can significantly facilitate the formation and growth of the Al15(FexMn1-x)3Si2 phase and also the growth of the continuous metallurgical bonding layer, but it inhibits the formation of the needle-like Al5FeSi phase. Furthermore, when the Mn content is 1.5wt%, a significant improvement has been made in the metallurgical bonding at the Al/Fe interface under the condition of hot dipping at 720℃ for 2min.For improving Al/Fe bimetal composite casting process and reducing the production cost, this paper attempts to use the pure zinc or zinc alloy as the hot dip melt. The results show that they all can promote the metallurgical reaction between aluminum alloy and iron and effectively control the thickness of the continuous metallurgical bonding layer. With hot dipping time increasing, the thickness of the transition layer in aluminum substrate increased significantly. The high-pressure torsion (HPT) test shows that the Al/galvanized steel interface has the better plastic property than Al/aluminized steel interface under high pressure environment. In addition, the HPT process strengthens the substrates of the aluminum alloy and steel. |
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