Influence of production systems and anodizing treatments on additively manufactured mechanical interlocking structures

Multi-materials are attracting increasing interest in today industries as a means of producing highly functional and lightweight components. As they become more widely used in engineering applications, especially in the automotive and aerospace sector, metal-composite components are of particular interest. Effectively joining these materials can be challenging due to their fundamentally different chemical composition and mechanical properties. A recent development in joining techniques involves the use of mechanical interlocking structures, which are arrays of protrusions formed on the surface of one of the two materials to be joined. By exploiting the geometries of these structures and their roughness, the second material to be joined can be locked to the first one, without the need for additional joining methods, such as adhesives or fasteners. Additive manufacturing can be used to produce interlocking structures due to its unique ability to build complex shapes, resulting in a single-step manufacturing process that reduces both cost and time. At first, particular attention was paid to the design phase of the interlocking structures. Afterwards, AlSi10Mg substrates with interlocking structures were manufactured using the powder bed fusion technique, using a laser beam as energy source (PBF-LB). Two different PBFLB systems were used, and the samples produced were compared by means of metallographic characterizations. Finally, different electrochemical treatments and bath conditions were investigated to evaluate the feasibility and the effects of performing an anodizing process on the 3D metal surfaces. An arrow-shaped geometry was chosen after an extensive literature review. Both PBF-LB systems were able to produce the geometry, but one system achieved better geometry accuracy. The morphology and properties of the anodic layer on the different areas of the PBF-LB samples were analyzed and correlated with the anodizing process parameters. The metallographic characterization of the samples suggested that there is a strict correlation between the geometrical accuracy of the interlocking structures and the PBF-LB building conditions. Therefore, particular attention should be given to these aspects. In addition, anodizing surface treatments on the metal surface could be performed, highlighting the difficulty of developing an oxide layer on a 3D surface of complex shape.