Development of friction stir powder additive manufacturing process and its use for lightweight alloys and composites

Abstract

Components made of high-strength aluminum (Al) alloy are widely used in aerospace, automobiles, marine, sporting equipment, and other critical applications. However, these components need to be replaced or repaired due to the damage caused by corrosion, wear, and impact. Replacement is expensive, time-consuming, and inefficient approach whereas repair is cost effective, faster, and efficient strategy. In the context of these requirements, additive manufacturing (AM) has played a significant role in recent years. American Society for Testing and Materials (ASTM) defines additive manufacturing (AM) as a “process of joining materials, usually layer upon layer as opposed to subtractive manufacturing process, to make an object using data of its 3D-CAD model”. AM is one of key enablers of Industry 4.0. It manufactures a product by depositing the materials either vertically or horizontally or both horizontally and vertically producing multi-layer single-track, single-layer multi-track, and multi-layer multi-track deposition respectively. AM processes are primarily divided into two categories: (i) Fusion based additive manufacturing (FBAM) and (ii) Solid-state additive manufacturing (SSAM). The FBAM processes involve melting of the feedstock material therefore they suffer from various solidification related defects (i.e., porosity, shrinkage, and hot cracking). Moreover, most of the FBAM processes are costlier and provides lower deposition rates. However, they are more prevalent in industries and have drawn the attention of more researchers globally. Use of FBAM processes for Al alloys makes the deposited layer prone to grain coarsening, oxidation, evaporation, thermal stresses, and thermal cracking due to involvement of more amount of heat. These aspects restrict the use of FBAM processes in manufacturing better quality depositions of Al alloys with consistent isotropic properties. Therefore, new additive technologies such as SSAM processes which do not melt the feedstock material, are required to overcome these challenges. Ultrasonic additive manufacturing (UAM), cold spray additive manufacturing (CSAM), friction stir additive manufacturing (FSAM), and additive friction stir deposition (AFSD) are reported as SSAM process in the literature along with their potential applications in hard facing, corrosion protection, damage repair, cladding, and additive manufacturing. Absence of melting of feedstock material in the SSAM processes helps them to minimize the solidification related or fusion-based defects such as porosity, shrinkage, and hot cracking. They can be used for a broad material range of ferrous and non-ferrous materials. They are more energy-efficient, do not produce any harmful gases, produce fine-grained equiaxed microstructures, give better mechanical properties of the manufactured product than the FBAM processes, and provide solutions to the drawbacks of FBAM processes. Consequently, the SSAM processes are referred to as green additive manufacturing processes.