Application of electric discharge process in joining aluminum and stainless steel sheets

Abstract

By the process using electric energy, two-ply sheet laminates of aluminum (A1100)–stainless steel (SUS430) have been made without the reduction in the thickness of the both sheets. The A1100–SUS430 layered sheets were finally resistance-heated at 833 K for 0.4–3.6 ks under an applied pressure of 30 MPa after the pulsed electrical discharge for 0.7 ks. The true shear strength of the joined interface shows almost the constant value of 60–68 MPa to the holding time of 1.8 ks at 833 K. The true shear strength is close to that of A1100 sheet, which means satisfactory joining is achieved. After the holding time of 2.7 ks, the true shear strength is reduced to 30 MPa, due to the creation of a continuous intermetallic compound layer. The values of the joined area fraction at the A1100–SUS430 interface are changed from 25 to 70% for the laminates resistance-heated for 0.4–3.6 ks at 833 K. Little change of the joined area fraction are shown in the laminates resistance-heated for the holding times of more than 1.8 ks. It is suggested on the basis of the result of the thermal calculation that the maximum value (70%) of the joined area fraction is due to inhomogeneity of the surface-temperature on the SUS430 side at the A1100–SUS430 interface by the heat release because the SUS430 sheets is wider than the base surface of the graphite punch. For application of the process using the electric energy in joining the metallic sheets, it is important to avoid the inhomogeneities of electric current and temperature distribution through the interface between the sheets to be joined.