Evaluation of Microstructural, Mechanical and Corrosion Behaviours of Laminated AA6061/AA7075 Metal Matrix Composites Build by Friction Stir Additive Manufacturing for Structural Applications

The structural performance of metallic components is a significant challenge especially when it comes to operating conditions in real-world applications. Friction stir additive manufacturing (FSAM) is a solid-state additive manufacturing (AM) that provides controlled microstructure with homogenous grains and excellent structural performance. In this study, the FSAM technique was utilized to fabricate a lightweight laminated AA6061/AA7075 metal matrix composite with improved mechanical properties. The feasibility of the FSAM was demonstrated to build multi-functional, multi-material components for aerospace, automotive, and defence industries to enable lightweight, high-strength components. The FSAM tool was designed with an optimum shoulder length, shoulder diameter, pin length, and pin diameter considering the plate thickness. Afterward, optimized process parameters were designed using the Taguchi L9 orthogonal array (OA) technique. Microstructural features and their effect on mechanical properties such as microhardness and ultimate tensile strength (UTS) were evaluated in the FSAM build. FSAM build improved in microhardness (from 107±1.2 to 138.4 ±2.8 HV_0.2) and tensile strength (from 310 to 384 MPa) as compared to base material AA6061. Corrosion resistance was also studied to understand the feasibility of the FSAM technique in various environmental conditions. The overall performance of the FSAM build shows promising results compared to the base materials.

Keywords:
Friction stir additive manufacturing; Aluminum alloys; Taguchi technique; Microstructure; Microhardness; Corrosion resistance