Environmental concerns related to greenhouse gas emissions have provided the impetus to develop
next-generation lightweight materials for automotive components, especially for passenger cars.
Weight reduction in automobiles means reduced fuel consumption and better fuel efficiency.
Aluminium alloys are well suited for such applications owing to their low density and structural
integrity. Newly developed medium-strength, high-elongation (Al-Zn-Mg)-Fe (HE700) alloys for
structural shape casting applications have the potential to fulfill the demand for significant
lightweighting of components over conventionally used cast aluminium alloys. The alloy used in
the present work is basically a dilute hypoeutectic Al-Fe system with Zn and Mg as strengtheners
and Ti as a grain refiner. Near net shape HE700 alloy plates were processed by high vacuum high
pressure die casting (HVHPDC) route. Joining such shape-casting alloys to form a high-integrity
component assembly is a critical process in structural lightweighting. As aluminium alloys such as
Al-Zn-Mg are susceptible to hot tearing during solidification, a solid-state joining technique, i.e.,
friction stir welding (FSW), has been used to join the plates in this research work. The critical
process parameters such as rotation and traverse speed have been optimized through a detailed
microstructural study and mechanical property evaluation of the welds. A major emphasis of the
work is on the understanding of microstructural evolution, especially with regard to the precipitates
and the eutectic (intermetallic) phase present in the alloy. Tools like high-resolution transmission
electron microscopy (HRTEM), atom probe tomography (APT) and high-angle annular dark field
(HAADF) technique have been used for the same. Also, different strategies are explored to
minimize the extent of the heat-affected zone (HAZ) without compromising the weld quality. The
study will thus establish a viable window of processing parameters for joining the new generation
HE700 alloy and also form a basis for dissimilar FSW of HE700 alloy with other automotive-grade
materials to expand its scope for automotive light-weighting applications.