Simulations of the welding process for butt joints using finite element analysis (FEA) of the effect of porosity are presented. The metal used was aluminium alloy (grade 2024), and the filler material was alloy ER5356. The simulations were performed using the commercial software ANSYS, considering a double ellipsoid heat source, temperature-dependent material properties, material deposits, mechanical analysis, transient heat transfer, and defects (porosity). In this study, the FEA simulations were constructed for two types of heat source (singleand double-ellipsoid) used in gas tungsten arc welding (GTAW), and the calculated residual stress results were compared with the experimental values. Two double ellipsoid models were constructed for cases with and without porosity. The porosity was measured by three-dimensional (3D) computed tomography (CT), and the size and location of pores were mapped onto the weld bead created by the birth-and-death technique.

Aluminum alloys are used widely in many applications due to its low in density which can lead to a lightweight product. A high percentage of Cu in the chemical composition of the 2024 aluminum alloys helps withstand the occurrence of corrosion as well. Thus, aluminum alloy grade 2024 is used as a material for several parts in aircraft and spacecraft components, (e.g. the body of commercial airplanes), as well as parts in many other applications. Gas Tungsten Arc Welding (GTAW) is used widely in joining material parts together. Inappropriate welding parameters usually cause problems such as porosity in the welding. The occurrence of porosity is undesirable in welding because it can affect the strength of the welding area as well as other properties. Tensile residual stress near the surface of the material expedites the fatigue crack initiation. The relationship of porosity and residual stress for GTAW parts was very limited in literatures. Therefore, the objective of this research was to investigate the relationship of porosity to the occurrence of residual stress after the welding process. Full factorial design of experimental technique was used for setting up welding conditions of the GTAW. The specimen with highest porosity was selected for further analysis of its effect on residual stress. Porosity was analyzed by the radiographic testing (RT) and the residual stress was measure by X-ray diffraction (XRD) using sin2 method. The results showed that the highest porosity in the welded bead was found at the current of 130 A, the welding speed of 210 mm./min., and the wire feed rate of 700 mm./min. The results also suggested that lower current and welding speed caused an increase in porosity. The residual stress results on both longitude and transverse directions showed tensile residual stress at locations around the welded bead area.

In this paper, we propose hot-wire plasma welding, a combination of the plasma welding (PAW) process and the hot-wire process in the additive manufacturing (AM) process. Generally, in plasma welding for AM processes, the deposit grain size increases, and the hardness decreases as the wall height increases. The coarse microstructure, along with the large grain size, corresponds to an increase in deposit temperature, which leads to poorer mechanical properties. At the same time, the hot-wire laser process seems to contain an overly high interstitial amount of oxygen and nitrogen. With an increasing emphasis on sustainability, the hot-wire plasma welding process offers significant advantages: deeper and narrow penetration than the cold-wire plasma welding, improved design flexibility, large deposition rates, and low dilution percentages. Thus, the hot-wire plasma welding process was investigated in this work. The wire used in the welding process was a titanium American Welding Society (AMS) 4951F (Grade 2) welding wire (diameter 1.6 mm), in which the welding was recorded in real time with a charge-coupled device camera (CCD camera). We studied three parameters of the hot-wire plasma welding process: (1) the welding speed, (2) wire current, and (3) wire feeding speed. The mechanical and physical properties (porosity, Vickers hardness, microstructure, and tensile strength) were examined. It was found that the number of layers, the length and width of the molten pool, and the width of the deposited bead increased, while the height of the layer increased, and the hot-wire current played an important role in the deposition. In addition, these results were benchmarked against specimens created by a hot-wire plasma welding/wire-based additive manufacturing process with an intention to develop the hot-wire PAW process as a potential alternative in the additive manufacturing industry.

The purpose of this study is to investigate the forming characteristics of single-pass Metal Inert Gas (MIG) welding wire for multi-layer additive manufacturing parts. Influences of arc current, arc voltage, arc distances, welding speed, wire feed speed, temperatures and heat input on layer formation were analyzed. The deposition of material by MIG process is controlled by a robot (ABB) controller for constructing walls of rectangular box shape. The samples were measured with a microhardness testing and tensile testing onto the welded bead created by the additive manufacturing technique. It was found that the mechanical properties of microhardness values are between 151.70 to 155.80 HV and the tensile strength values are between 472.71 to 491.12 MPa according to transverse and longitudinal sections of the specimens.