Evolution of Interface Microstructure and Tensile Properties of AgPd30/CuNi18Zn26 Bilayer Laminated Composite Manufactured by Rolling and Annealing

Abstract

An AgPd30/CuNi18Zn26 bilayer laminated composite (BLC) was manufactured by hot-roll bonding followed by two passes of cold-rolling and three passes of annealing. The evolution of the interface microstructure during the manufacturing process was investigated using a scanning electron microscope, an electron probe microanalyzer, an X-ray diffractometer and a transmission electron microscope. It was found that a net atomic flow of Zn and Cu immigrated from the CuNi18Zn26 layer into the AgPd30 layer, leading to the formation of a Cu3Au-type superstructure of Cu2NiZn in the former and a diffusion layer in the later. The clusters enriched in Zn and Pd were formed in the diffusion layer and their number varied during the rolling and annealing process. The thickness of the diffusion layer was increased by annealing and decreased by cold rolling. Several intermetallic compounds were identified, which are Pd2Zn, PdZn, Pd2Zn3, PdZn2, Pd3Zn10 and Cu3Pd. Some orientation relationships between the compounds and the AgPd30 alloy were determined to be (310)PdZn2//(111)AgPd and (114)Cu3Pd//(311)PdZn2//(321)Pd3Zn10. Delamination occurred in all 6 samples during tensile testing, including an as-bonded one, two as-rolled ones and three as-annealed ones, but its degree decreased successively with the progress of rolling and annealing. Two turning points appear on the tensile curves of as-annealed samples, which are ascribed to the initiation of delamination and the yield of the metal matrix. However, the tensile curves of the as-bonded and as-rolled samples are smooth.