A comparative study on the formability of aluminum bipolar plate with channels using indirect squeeze casting and stamping

Abstract

In this study, a fuel cell bipolar plate is formed using indirect squeeze casting which uses liquid materials and stamping process which uses solid state materials. The formability of these two types of processes is discussed. The shapes of die cavity in the indirect squeeze casting and that in the stamping are same. The materials filling rate during indirect squeeze casting was increased as punch pressure that pushes molten aluminum into cavity of die is increased. A breakage occurs when load of upper die which presses aluminum plate 0.1mm thick is at 20 kN. When load of upper die is at 15 kN, the maximum channel depth is achieved. Though precise channel shape can be achieved by the indirect squeeze casting, the thickness of bipolar plate is larger by around three times than that formed by stamping. An irregular-shaped channel is obtained in the bipolar plate formed by stamping due to problems of wrinkle, springback, and flatness. The current density of unit cell with casted aluminum bipolar plate with TiN layer and stamped aluminum bipolar plate are 421 and 410 mA cm−2 at 0.6 V, respectively.