An investigation of the effect of steel alloying elements on iron-aluminum intermetallic characteristics for dissimilar resistance spot welding
Luke Walker, Wei Zhang
Abstract
• Be, Si, Ti, V, Cr, Co, Ni, Ga, Ge, and Mo were tested for dissimilar Al-steel welding. • Ti, V, and Ga increased the strength of the aluminum-to-steel spot welds the most. • Ti, V, and Ga decreased the formation of FeAl intermetallics at the weld edges. • Ti, V, and Ga decreased the driving force for the formation of Fe 2 Al 5 out of liquid. • Results help bridge the gap between experimental testing and theoretical calculations. Iron (Fe) and aluminum (Al) are the two most widely used metals in manufacturing industries. However, welding aluminum to steel is limited by the formation of brittle intermetallics. This leads to a fundamental question, what if additional alloying elements could decrease Fe-Al intermetallic formation? Many studies have approached this question experimentally and theoretically. However, there is a lack of uniform experimental testing to link experimental results with theoretical calculations. The purpose of this study is to offer extensive experimental results in order to help verify the theoretical calculations that have been done on this topic. After studying the literature, the ten elements selected were: Be, Si, Ti, V, Cr, Co, Ni, Ga, Ge, and Mo. Iron-based interlayers alloyed with these elements were fabricated and used to create dissimilar resistance spot welds between aluminum and steel. The welds were tested in the cross-tension configuration, and the intermetallics were characterized for composition, thickness, and hardness. The elements that increased weld strength the most were Ti, V, and Ga because they decreased intermetallic formation at the weld edges. This is because these elements decreased the driving force for the formation of Fe 2 Al 5 , according to thermodynamic calculations.