Effect of Cooling Rate on the Microstructure and Mechanical Properties of Cu/Al Bimetal Fabricated by Compound Casting
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AS a hybrid composite, Cu/Al bimetal combines the good electric and thermal conductivities of Cu with low density, light weight, and corrosion resistance of Al.[1] Cu/Al laminated composites have been widely used in automobiles, electricity, decoration, etc. Numerous techniques have been applied to fabricate Cu/Al clads, such as rolling,[2] rotary swaging,[3] friction stir welding,[4] brazing,[5] compound casting,[1] and Horizontal Core-Filling Continuous Casting.[6] Among these methods, compound casting, as a solid–liquid bonding method, has displayed enormous superiority in fabricating irregular shapes of Cu/Al bimetallic products. Researchers have paid great attention to the Cu/Al solid–liquid bonding methods. Tavassoli et al.[7] have reported that the effect of the preheat temperature of solid Cu is far more important than that of the pouring temperature of Al melt on the formation, thickness, and type of the intermetallics. Hu et al.[8] and Liu et al.[1]
GUOPING LIU, QUDONG WANG, LI ZHANG, BING YE, HAIYAN JIANG, and WENJIANG DING are with the National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, 200240 Shanghai, P.R. China. Contact e-mail: [email protected] Manuscript submitted August 1, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
have investigated the effects of the coating materials and the thickness of coating on the microstructure, mechanical, and electric properties of Cu/Al bimetals. Some researchers fabricated Cu/Al solid–liquid diffusion couples to study the reaction thermodynamics and kinetics. For example, Tanaka et al.[9–11] have found that the migration distance of the L/e2 interface is much larger than the total thickness of the compound layers. Under different gradient magnetic field conditions, Wang et al.[12,13] investigated the growth of diffusion layers at the Cu/Al interface and found that high magnetic fields can suppress the natural convection and induce the thermoelectromagnetic convection at the solid/liquid interface. To date, few researches have investigated the effect of the cooling rate on the microstructural evolution and mechanical properties of Cu/Al bimetal. The cooling rate has a great impact on the microstructural characters of the given system, such as the grain size, the eutectic lamellas spacing and the interfacial morphology. Also, the dissolution of solid Cu substrate and the formation of compounds during solid–liquid fabrication process occur in a nonisothermal condition. In this way, the study of the interfacial transformation is of great necessity, and significance. Comprehensive understanding of the interfacial formation mechanism is another vital topic for solid–liquid bonding method, and it has attracted extensive researches up to now. Tavassoli et al.[7] deduced that Al2Cu is the first phase to grow on the solid Cu due to
its special tetragonal structure and composition. Wang et al.[14] studied the interfacial diffusi
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