Experimental and Theoretical Research on the Corrosion Resistance of Ferrous Alloys in Aluminum Melts
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DURING the fabrication and processing of aluminum including melting,[1] forming,[2] and hot dip aluminizing,[3,4] many metal components are immersed into aluminum melts. They are often subjected to severe corrosion, which in turn shortens their service lives and results in the contamination of aluminum melts, degrading the efficiency of aluminum processing and product quality.[5,6] Although refractory metals, such as Nb, Mo, W, Co, and their alloys, have excellent resistance to aluminum corrosion,[7–11] they are costly and difficult to synthesize, greatly limiting their applications. To minimize the corrosion of metal components, the demand for low-cost metal materials with high corrosion resistance has become increasingly urgent in the field of aluminum processing. Gray cast iron is commonly used for tooling and structural components required for processing of aluminum melts due to excellent corrosion resistance, easy molding, and low cost. However, it has low strength at high temperature and is easily oxidized to cause growth GAOPENG XU, KUI WANG, XIANPING DONG, HAIYAN JIANG, QUDONG WANG, BING YE, and WENJIANG DING are with the National Engineering Research Center of Light Alloy Net Forming and the State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P.R. China. Contact e-mail: [email protected] Manuscript submitted January 22, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
cracking. Alloying is usually utilized to improve its comprehensive property. Conversely, ductile iron has poor corrosion resistance, but good resistance to thermal fatigue and oxidation. It is widely used in the production of hot-worked aluminum.[12] Additionally, the corrosion resistance of H13 is poor as well, but has excellent thermal stability, high temperature strength, wear resistance, thermal fatigue resistance, and oxidation resistance.[13] As a result, it is often used as aluminum alloy die-casting mold and extrusion die. Nevertheless, the ferrous alloys mentioned above are inevitably subjected to different degree of corrosion when applied in aluminum melt environment. The reactions between aluminum melts and ferrous alloys can lead to the formation of different intermetallic compounds (IMCs). However, not all IMCs can be formed during hot dipping tests. Numerous studies[14–19] show that the ferrous alloy can react with the aluminum melts to form the IMC layer that mainly contains Fe2Al5 and FeAl3, and the exfoliation of IMCs can lead to the corrosion of ferrous alloys. Sidhu[14] suggested that the presence of C-rich phases, graphite flakes, and cementite was effective in enhancing the aluminum melt corrosion resistance of gray cast irons, and the graphite morphology can play a pivotal role in aluminum melt corrosion resistance. Balloy et al.[15] also found that the graphite flake is favorable for the diffusion inhibition of Al atoms during the corrosion of the cast iron in aluminum melts. However, the influence mechanisms of the morphology and distribution of graphite and carbide on the
