Grain size effect in cold roll bonding of copper-steel and brass-steel sandwiches

Cold roll bonding tests were performed with three-layer sandwich materials, consisting of mild steel core, copper and 76/24 type α-brass claddings of varying grain sizes. Two bonding stages were recognized: 'selective', when the volume fraction of the components can be changed, and a 'coextrusion' stage, when welding occurs due to extrusion of copper and brass into the microcracks developed at the steel surface. Volume fraction variation and welding conditions were different for the two cladding materials, and also grain size dependent in the case of brass. The interfacial morphology has indicated that the inherent deformation behaviour of the tested cladding materials, affected by stacking fault energy and grain size, seems to be important in controlling the overall bond strength in cold roll bonding.