SGER: Friction Bit Joining - A New Solid State Spot Joining Process

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The objective of this Small Grant for Exploratory Research (SGER) project is to study the capability of a new solid state joining process, termed friction bit joining, to weld dissimilar combinations of aluminum, magnesium and steel automotive sheets. The automotive industry and the US Government are aggressively pursuing use of lightweight materials such as Mg alloys and Al alloys in auto body structures for improved vehicle fuel efficiency. High-volume production vehicles would require use of a variety of engineering materials, ranging from ultra high-strength steels (UHSS), Al alloys, Mg alloys and others to meet cost and performance objectives. The combination of lightweight materials with widely acceptable structural materials such as UHSS presents a number of technical challenges in automotive body-in-white assembly. One of them is joining different materials to form an integrated structure component which meets design and performance requirements. The current work will study the welding process from a fundamental viewpoint, including the effect of process conditions on metallurgical bond properties of dissimilar alloy joints. The friction bit joining process has been shown to be capable of achieving high levels of strength in dissimilar alloy joints of DP 980 steel and 5754 aluminum alloys during a preliminary study. This combination of ultra high strength steel and a soft aluminum alloy would be difficult or impossible to join using conventional spot welding or even self piercing riveting.If this new process is shown to be successful in bonding dissimilar metal alloys where strength levels are very different, it will promote greater use of light metals in automotive and other transportation structures, allowing for reduced weight and improved fuel efficiency.