# Mechanical Properties Analysis of WAAM Produced Wall Made from 6063 Alloy Using AC MIG Process
## 1 Introduction  
Wire and arc additive manufacturing (WAAM) is a type of additive manufacturing that works according to the principle of wire arc direct energy deposition (WA-DED). In this process, a metal wire is used as feedstock and melted by an energy source, usually an electric arc, but possibly also a plasma arc, laser or electron beam, and then deposited layer by layer to build up a three-dimensional structure [1]. The additive manufacturing of large-volume components makes WAAM one of the most efficient direct energy deposition (DED) processes when it comes to achieving a low buy-to-fly (BTF) ratio, resulting in significant cost savings [2]. Therefore, WAAM is especially beneficial for producing expensive and high-performance materials such as titanium and nickel alloys, high-strength steels and aluminum alloys, which are normally difficult to machine [3]. This study deals with the limited existing research on WAAM of 6063 alloys, especially using AC MIG with different EN ratios. By evaluating mechanical and microstructuralbehavior under controlled polarity balance, this research aims to identify process-property correlations and optimize manufacturing quality for potential structural applications. Aluminum alloys have several desirable properties, including low density, high specific strength, good thermal and electrical conductivity and excellent corrosion resistance and formability. When processed using WAAM, aluminum alloys can exhibit mechanical properties that are comparable to or even better than their wrought counterparts [4; 5]. However, despite these advantages, WAAM-produced aluminum components often suffer from process-related defects that limit their wider industrial application. These challenges are primarily related to process stability such as path planning, parameter optimization and melt pool shielding as well as alloy chemistry [6]. The most critical problems with aluminum WAAM are the formation of porosity, residual stress and deformation and solidification cracking [7]. Porosity in WAAM is caused by various factors such as the arc welding process, process parameters, interlayer temperature, wire quality and alloy composition and can be exacerbated in multilayer build-ups by the heat input from the subsequent layers, which promotes pore growth [8]. Pores can reduce mechanical properties such as yield strength, contribute to anisotropy and reduce tensile strength, while the choice of deposition strategy, the type of shielding gas and the gas flow rate have a direct influence on porosity growth [9]. The potential to reduce process-related defects in WAAM can be achieved by using modified GMAW techniques [10]. A significant advance is the development of the Cold Metal Transfer (CMT) process, which minimizes weld spatter by short-circuiting the arc through controlled dipping of the welding wire into the weld pool. This technique has been effectively applied to various aluminum alloys and has evolved into several improved variants, including CMT-P (pulsed), CMT-ADV (alternating polarity) and CMT-PADV (a combination of both), all of which contribute to providing better arc strike behavior and reliability, lower heat input and reduce the porosity and a refined microstructure [11]. An alternative solution that counteracts the cost and complexity of CMT is the implementation of the pulsed variable polarity GMAW (VP-GMAW) process, which provides comparable or better deposition efficiency at a lower process cost. This technique has demonstrated stable arc behavior, high deposition efficiency (up to 82.56%) and isotropic mechanical properties, making it a promising candidate for aluminum WAAM [12]. By comparing pulsed AC, pulsed, and CMT modes, it can be concluded that pulsed AC mode (with variable polarity) offers a significant improvement in porosity control, achieving porosity values up to ten times lower than conventional pulsed GMAW.