Microstructural development during wire arc additive manufacturing of copper-based components

Abstract

Wire arc additive manufacturing (WAAM) is attractive to replace conventional subtractive manufacturing techniques to produce unique, complex and large-sized components. However, the multi-pass deposition thermal cycles of a WAAM process often generate columnar grain structures in the microstructures of components. These components exhibit anisotropic mechanical properties, which render them unsuitable for major engineering applications. In this work, metal transfer characteristics in a gas metal arc (GMA)-based WAAM process and its influence on microstructural evolution were studied to propose an optimum deposition technique to generate equi-axed grains containing microstructures. Results showed that the microstructure of conventional pulsed mode deposition contained long and columnar grains while short-circuited deposition produced randomly oriented near equi-axed grains. High-speed camera imaging was used to study and optimize the metal transfer characteristics. Detailed microscopy analysis and tensile testing were carried out to confirm the isotropic nature of the deposits.