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Structural characteristics and corrosion properties of Cu/Sn–Pb composite produced by accumulative roll bonding process
Cu/Sn–Pb multilayer composite was fabricated by accumulative roll bonding (ARB) technique and its structural, mechanical, and corrosion properties were studied. Microstructural evolution revealed that distribution of Cu and Sn–Pb layers improves by increasing ARB passes and multilayer composite with wavy microstructure and formation of Cu6Sn5 intermetallic compound by solid-state reactions was achieved, while tensile test depicted that tensile strength and fracture strain decrease after the first ARB pass. However, the strength of the multilayered composite at the first pass (about 300 MPa) is much higher than that of the pure Cu (about 200 MPa). Electrochemical tests (potentiodynamic polarization) were conducted in 3.5 wt.% NaCl and boiler feed water (BFW) on the surface and cross-sectional areas. Open circuit potential (OCP) of the composite was lower than that of the pure and ARBed Cu (pure Cu was fabricated using ARB process after seven passes). The results demonstrated that corrosion resistance on the surface and cross-sectional area decreased with increasing ARB passes, indicating a growing susceptibility to corrosion on both surfaces. Besides, with increasing ARB passes a more uniform distribution of Sn–Pb within Cu matrix was realized and due to the conversion of galvanic coupling to micro-galvanic coupling corrosion occurs more uniformly.