Friction stir-based additive manufacturing

Abstract

Additive manufacturing (AM) has completely altered the traditional component manufacturing and qualification paradigm. It provides unitisation and topological optimisation opportunities simultaneously. Broadly, the additive manufacturing processes are classified as fusion-based or solid-state. The solid-state additive manufacturing processes are relatively nascent. Among these, friction stir-based processes involve intense shear deformation of material while building. In this review, we focus on friction stir additive manufacturing (FSAM) and additive friction stir deposition (AFSD). These friction stir welding derived techniques have ability to produce microstructures that lead to better mechanical properties than the conventionally processed parent alloys; in many cases overcoming the traditional strength-ductility tradeoff paradigm. The best way to capture this advantage is to conduct materials selection for build which benefit from the attributes of these processes. This review provides a systems approach framework and a conceptual process model to guide researchers. A case is built that the best mechanical properties can be obtained by alloy design for such disruptive and innovative manufacturing processes. The intrinsic and extrinsic limitations are highlighted to guide researchers in the field of FSAM and AFSD. While AFSD is readily applicable to lower melting temperature materials currently, applying it to high-temperature materials requires significant research and development on tool materials. Examples of materials processed by FSAM/AFSD include aluminium alloys, magnesium alloys, titanium alloys, steels and nickel-base superalloy. A physics-based process modelling framework applicable to FSAM/AFSD is provided. To fully validate such models, it is imperative to use machines with appropriate sensors that capture the machine parameters, tool health, and workpiece temperature.