Interface Zone Microstructure of the Explosively Cladded Copper on Steel

This study is dedicated to the Cu/P265GH steel interface zone produced by explosive welding subjected to stress relief annealing followed by the complex microstructure characterization. The analysis was carried out with aim of the variety of scanning and transmission electron microscopy techniques. Presented characteristics showed that the interface zone was continuous and of wavy morphology with locally visible melted zones under the wave vortices consisting of the joined materials. On the other hand, chemical compositions changes across the apparently sharp interface (metal/metal bond) in-between the waves showed copper-iron diffusion across the bonding interface. High-magnification observations of this interface confirmed the formation of a thin nanocrystalline interlayer of about 150 nm in thickness, composed of Cu and Fe mixed grains. Electron backscattered diffraction analysis evidenced the presence of annealing twins within the copper grains and also slight texturing of the copper grains toward <111>, being perpendicular to the plane of the weld. Moreover, for the first time, dilatometric measurements of Cu/P265GH steel clads were performed in the temperature range of 25–600 °C, revealing that the thermal expansion values were within the range of the reference materials—copper and steel. These preliminary studies showed that the obtained thermal expansion values of the investigated platers were exactly between the values for the reference materials Cu and P265GH steel.