Application of resistance heating technique to mushy state forming of aluminium alloy

Abstract

The feasibility of mushy state forming of aluminium alloy making use of resistance heating was examined. Aluminium alloy (A357) was used as an experimental material and billets of rectangular prism with a cross-section 10 mm 2 and height 20 mm were used for heating and forming experiments. Input heat control was applied to the billet heating and the insertion of thin discs of austenitic stainless steel with a low thermal conductivity between the billet and copper electrodes was used in order to improve the efficiency of the billet heating. Results were summarised as follows. (1) Insertion of the discs was very helpful in heating the billet to its mushy state. (2) The force applied to the electrodes to ensure the electrical contacts being too small, sparks occurred and welds arose between the billet and discs. Contact pressure of more than 19.6 MPa was needed at the start of electrification to avoid the welding. (3) Mushy state upsetting in a container and forming with a shaped die were both successfully performed using input heat control.