Microstructure and mechanical properties of dissimilar friction stir welded joints of laser powder bed fusion processed AlSi10Mg and conventional hot rolled 6061-T6 thin sheets

Abstract

In recent years, laser powder bed processed metal components have been extensively used in the aerospace and high-end automobile industries. However, this technology remains expensive in terms of the material and size limitations of the printing beds. In the present study, an alternative solution is suggested to overcome these challenges in the context to adopt the technology more effectively. For the first time, an attempt was made to join the two dissimilar materials fabricated through different technologies using friction stir welding. Laser powder bed fusion processed AlSi10Mg alloy and conventional hot rolled AA6061-T6 aluminium alloy were selected as a base material. The study aims to reveal the role of the positioning of the alloys and the effect of heat input on the microstructural characteristics and joint properties of the welded joints. The analysis of the microstructure shows the formation of the onion ring structure and thin banded patterns while positioning of AlSi10Mg material on the advancing side at high heat input. Meanwhile, the fraction of HAGBs was uniformly and highly dominated at high tool rotational speed, regardless of material positioning. Although, the dispersion of eutectic Si-particles (from the Si-rich network of AlSi10Mg) over the solid solution of Al-matrix was enhanced in the stir zone. The results of microhardness show a considerable drop in the welded zones as compared to both the base materials. The tensile properties of the welded joints were also significantly affected by the material positioning and heat input. The maximum UTS was achieved when a joint was fabricated with high tool rotational speed and AlSi10Mg positioned on the advancing side. The key findings from the present study proved a good reference for engineering applications, where the complex and large additive components are replaced by the hybrid components.