Mechanical Characteristics of a Roll-Bonded Cu-Clad Steel Sheet Processed Through Incremental Forming

Incremental sheet forming (ISF) is an emerging cold forming process with a high economic payoff. In this study, the influence of the ISF process on the tensile properties of Cu-clad Steel sheet is analyzed experimentally. Depending on the forming conditions, the post-ISF values of yield strength, tensile strength, and ductility are found to range from 161 to 430, 288 to 449 MPa, and 4.93 to 16.62 pct, respectively. These properties show a strong dependence on several correlated quantities such as the applied plastic strain, grain size, and mean residual stress. As the plastic strain increases from 0.08 to 0.8, the width of the grain decreases from 8.11 to 5.78 µm and the residual stress increases from − 15 to − 131 MPa. In comparison to the unformed sheet, ISF enhances the yield strength (4.6 to 117 pct) and tensile strength (0.6 to 73 pct). The nature of change in ductility (− 67 to 117 pct), however, depends on the process conditions, especially the state of the unformed sheet (i.e., rolled/annealed) and the value of applied strain. In general, the rolled (or prestrained) sheet upon ISF experiences an increase in ductility. The annealed sheet, however, sees a drop in ductility when the forming strains are low (e.g., < 0.4) and an increase in ductility when the strains are high (e.g., > 0.4). X-ray diffraction (XRD) and electron dispersive spectroscopy (EDS) analyses confirm that no new phase formed during ISF.