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

这一探索性研究小资助金(SGER)项目的目标是研究一种名为摩擦钻头连接的新型固态连接工艺焊接不同组合的铝、镁和钢汽车板材的能力。汽车行业和美国政府正在积极寻求在汽车车身结构中使用镁合金和铝合金等轻质材料，以提高汽车的燃油效率。大批量生产车辆将需要使用各种工程材料，从超高强度钢(UHSS)、铝合金、镁合金和其他材料，以满足成本和性能目标。轻质材料与广泛接受的结构材料(如UHSS)相结合，给汽车白车身组装带来了许多技术挑战。其中之一是将不同的材料结合在一起，形成满足设计和性能要求的一体化结构构件。本工作将从基本的角度研究焊接过程，包括工艺条件对异种合金接头冶金结合性能的影响。初步研究表明，摩擦钻头连接工艺能够在DP 980钢和5754铝合金的异种合金接头中获得较高的强度。这种超高强度钢和软铝合金的组合将很难或不可能使用传统的点焊甚至自冲铆接。如果这种新工艺被证明成功地结合了强度水平非常不同的不同金属合金，它将促进汽车和其他运输结构中更多地使用轻金属，从而减轻重量并提高燃料效率。

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.