Evaluation of mechanical properties of cold roll bonded mild steel and aluminum

Abstract

Abstract The need for joints between dissimilar materials often is used in automobile industries, electrical components and so on. This need of dissimilar metal joining is fulfilled by various solid state welding processes. Cold roll bonding (CRB), as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing large layered composite sheets and foils. It has various advantages such as good surface quality, low cost, fast process, easy to automate and no additional equipments except rolling mills are required. In this research work, CRB of Mild Steel (MS) and wrought Aluminum (w-Al) strips was studied. Bonded sheets of w-Al and MS are used for cylinder liners and bearings. CRB of w-Al and MS sheets was carried out on two high rolling mill. These bonded sheets were then diffusion bonded with permutations of temperature and time to find out the probable phases at the interface and the intermetallic compound layer thickness. Effect of the processing parameters on bonding strength, microstructure, hardness and grain-size and the formed intermetallic phases were also studied. The tensile shear strength of the CRB strip increased to a maximum of 48.95 MPa with increase in reduction to 27%. As temperature and time of diffusion bonding increases, the thickness of intermetallic compound layer increases. During heat treatments, there was considerable Al diffusion into the MS or in other words Fe side near the interface where Al-rich intermetallics formed. XRD analysis confirmed this with the presence of high intensity peaks of aluminium rich intermetallic compounds e.g Fe2Al5, FeAl3 and FeAl2 at the interface. The activation energy for diffusion of Al to Fe was found to be 160 KJ/mol.