Self-Piercing Riveting (SPR) of Magnesium High Pressure Die Castings

As a technology successfully employed on joining aluminum and steel, Self-Piercing Riveting (SPR) is yet to be established for magnesium alloys. Due to magnesium’s limited slip systems at room temperature, the main issue with the development of magnesium SPR technology is the magnesium button cracking. Several techniques have been proposed by researchers to address this problem, including pre-heating magnesium, applying rotation to rivets during SPR, using a sacrificial layer and padded SPR. All of these methods require installation of new equipment or additional processing steps. The objective of the current work is to introduce a SPR technique which employs current existing SPR machines with minimal modifications to existing processes to create crack free joint between magnesium and aluminum. Experiments were carried out to join coupons of 1.0, 2.0 and 3.0 mm thick aluminum to AM60B magnesium high pressure die casting (HPDC) samples. Through the results, it was shown that the joint is formed which is crack-free both externally and internally with a joint strength of >4 kN. With the flexibility of material selection and the compatibility with existing SPR process lines, this SPR process has great potential to be an enabler for more SPR applications on materials with limited ductility.