Strength Improvement Through Grain Refinement of Intermetallic Compound at Al/Fe Dissimilar Joint Interface by the Addition of Alloying Elements

Dissimilar material joining between Al alloys and steel may be effective in decreasing the weight of automobile bodies. In this study, dissimilar lap joining of Al alloys containing certain alloying elements, such as Ni, Cr, Mn, Ti, or Si, to interstitial-free steel was performed by tungsten inert gas arc brazing, and the effect of the alloying element on the joint strength associated with the Al-Fe intermetallic compound layer at the dissimilar interface was examined. The addition of an appropriate amount of an alloying element to the alloy increased the joint strength; the addition of Ni exhibited the most effective improvement. The additions of some elements changed the grain structure of the η-Fe₂Al₅ layer but not its chemical composition. This is the first study to clarify that smaller grain size of η-Fe₂Al₅ correlated to greater strength of the Al/Fe dissimilar joint.