Insights into the microstructure evolution and mechanical behavior of dissimilar friction stir welded joints of additively manufactured AlSi10Mg and conventional 7075-T651 aluminum alloys

Abstract

Metal 3D printing through laser powder bed fusion (L-PBF) has revolutionised the manufacturing industry. However, size limitations and production costs persist as challenges for the 3D printing of metallic alloys. Thus, joining L-PBF components to other parts becomes a vital aspect to produce composite structures for engineering applications. Among the dissimilar joining of various non-ferrous alloys, the integration of L-PBF components with difficult-to-join materials, such as aerospace-grade AA-7XXX aluminum alloys, still remains an unaddressed industrial problem. To address this problem, the current study was carried out to investigate the feasibility of joining L-PBF manufactured AlSi10Mg alloy with a traditionally rolled AA7075-T651 alloy using friction stir welding process. In this study, the influence of the base material positioning and heat input on the mechanical and metallurgical characteristics of welded joints was examined, followed by their interrelationships for more efficient adoption of this technology. The results revealed that the base material placement significantly influenced the joint strength at low heat input but showed negligible impact at high heat input. The joints fabricated at high heat input exhibited higher hardness within the nugget zone owing to the higher concentration of MgZn2 and β-Mg2Si secondary-phase particles as compared to the joints fabricated at low heat input. Texture analysis of welds showed that the C {001} <110> shear component dominated the nugget zone when AA7075-T651 was placed on the retracting side. Whereas, the A1*/ A2* {111} <1‾12‾ >/{111} <112‾ > simple shear component was prominent when AA7075-T651 was placed on the advancing side of the joint. Finer grains and high dislocation density in the nugget zone at low heat input resulted in the maximum joint efficiency of 77% with respect to the AlSi10Mg alloy. In contrast, a coarse grain structure at high heat input reduced the joint efficiency to 74%. The findings from this research suggest friction sir welding to be an efficient method for dissimilar joining of additive components with conventionally manufactured parts.