Large-scale aluminum parts are used in aerospace and automotive industries, due to excellent strength, light weight, and the good corrosion resistance of the material. Additive manufacturing processes enable both cost and time savings in the context of component manufacturing. Thereby, wire arc additive manufacturing (WAAM) is particularly suitable for the production of large volume parts due to deposition rates in the range of kilograms per hour. Challenges during the manufacturing process of aluminum alloys, such as porosity or poor mechanical properties, can be overcome by using arc technologies with adaptable energy input. In this study, WAAM of AlMg5Mn alloy was systematically investigated by using the gas metal arc welding (GMAW) process. Herein, correlations between the energy input and the resulting temperature-time-regimes show the effect on resulting microstructure, weld seam irregularities and the mechanical properties of additively manufactured aluminum parts. Therefore, multilayer walls were built layer wise using the cold metal transfer (CMT) process including conventional CMT, CMT advanced and CMT pulse advanced arc modes. These processing strategies were analyzed by means of energy input, whereby the geometrical features of the layers could be controlled as well as the porosity to area portion to below 1% in the WAAM parts. Furthermore, the investigations show the that mechanical properties like tensile strength and material hardness can be adapted throughout the energy input per unit length significantly.

https://www.mdpi.com/1996-1944/13/12/2671/pdf

Wire Arc Additive Manufacturing (WAAM) of Aluminum Alloy AlMg5Mn with Energy-Reduced Gas Metal Arc Welding (GMAW).

Wire arc additive manufacturing is currently rising as the main focus of research groups around the world. This is directly visible in the huge number of new papers published in recent years concerning a lot of different topics. This review is intended to give a proper summary of the international state of research in the area of wire arc additive manufacturing. The addressed topics in this review include but are not limited to materials (e.g., steels, aluminum, copper and titanium), the processes and methods of WAAM, process surveillance and the path planning and modeling of WAAM. The consolidation of the findings of various authors into a unified picture is a core aspect of this review. Furthermore, it intends to identify areas in which work is missing and how different topics can be synergetically combined. A critical evaluation of the presented research with a focus on commonly known mechanisms in welding research and without a focus on additive manufacturing will complete the review.

The Current State of Research of Wire Arc Additive Manufacturing (WAAM): A Review

Wire Arc Additive Manufacturing is a near-net-shape processing technology which allows cost-effective manufacturing of large and customized metal parts Processing of aluminium in Wire Arc Additive Manufacturing is quite challenging, especially in terms of porosity In the present work, pore behaviour in Wire Arc Additive Manufacturing of AW4043/AlSi5(wt%) was investigated and a post-process monitoring approach was developed It has been observed that as the shielding gas flow rate increases, the porosity in aluminium parts also increases due to the rapid solidification of the melt pool by forced convection The higher convection rate seems to limit the escape of gas inclusions Furthermore, gas inclusions escaping from the melt pool leave cavities on the surface of each deposited layer Process camera imaging is used to monitor these cavities to acquire information about the porosity in the part The observations were supported by Computational Fluid Dynamics simulations which show that the gas flow rate correlates with the porosity in aluminium parts manufactured by Wire Arc Additive Manufacturing Since a lower gas flow rate leads to reduced convective cooling, the melt pool remains liquid for a longer period allowing pores to escape for a longer period and thus reducing porosity Based on these investigations, a monitoring approach is presented

Porosity in wire arc additive manufacturing of aluminium alloys

Additive manufacturing (AM) route is a promising approach for fabricating complex and lightweight metallic structures that have applications in various sectors such as automotive, aerospace, and biomedical industries. Laser, electron beam, and electric arc are the common power sources available for AM. Out of different metal AM techniques, wire-feed additive manufacturing has been considered as a promising alternative for fabricating metallic parts for various applications. As it provides a high deposition rate, material utilization, density, and low cost with a low risk of contamination and porosity compared to powder-based raw material. Gas metal arc welding-based additive manufacturing (GMAW-AM) is a speciﬁc approach based on wire-feed AM. This technology uses a low-cost equipment which is suitable for fabricating components with large geometries and moderate structural complexity. These advantages attract the researchers and production industries for further developments in GMAW-AM to enhance its deposition performance, process capability, and applicability in various fields. The quality of metal deposited in GMAW-AM is generally represented by the surface form, dimensional quality, mechanical properties, relative density, hardness, etc. The present paper encompasses the research developments that occurred in the field of GMAW-AM in recent years. This review begins with the GMAW-AM procedure, performance capability, identification of factors affecting the deposition performance, and strategies adopted to overcome these issues. Several aspects such as mathematical modelling, optimization, key process parameters, and their combinations for a wide range of wire electrode material and percentage contributions are also reviewed and depicted in detail. Also, a comprehensive conclusion of this review, along with future perspectives, is explored subsequently. The current review work will help future researchers to select different wire materials and GMAW-AM parameters to achieve better performances. Lastly, several future research directions are suggested, specifically the need of a framework for GMAW-AM processes for fabricating quality products with minimum distortion.

Gas metal arc welding based additive manufacturing—a review

Wire-arc additive manufacturing (WAAM) has received considerable attention in the past years due to advantages in terms of deposition rate, design freedom, and buy-to-fly ratio. Particularly, cold metal transfer welding has been used extensively allowing for precise process control during manufacturing. Processing parameters have to be adjusted to advance this novel fabrication technique to meet the alloys’ requirements with the aim of meeting property goals and increasing microstructural homogeneity. In the present contribution, the alteration of the building strategy during WAAM of an aluminum alloy via variation of the polarity sequence is suggested. These parameters allow adjusting the heat input and, thus, the component’s temperature and cooling rate. Firstly, the quality of the surface is improved using adjusted deposition parameters. Secondly, a deposition strategy with a lower thermal exposure of the alloy provides a more homogeneous microstructure in terms of grain size, grain morphology, and distribution of second phases. Thirdly, the burn-off of volatile elements is reduced with decreasing heat input. The observed microstructural changes also result in more homogeneous local mechanical properties. It is demonstrated that the adjustment of the polarity sequence is a strong tool to influence the microstructure during WAAM enabling increased exploitation of this innovative technology.

Control of macro-/microstructure and mechanical properties of a wire-arc additive manufactured aluminum alloy

4043 aluminium deposits were elaborated using a 3D print device equipped with a Cold Metal Transfer welding source. Two sets of process parameters leading to different average powers were compared in order to establish the relations between the powers and energies produced and the geometrical characteristics of the deposits. The effects of the travel speed and layer superposition on the transfer mechanisms as well as on the geometrical characteristics of the deposits were discussed for both sets of parameters. Finally, the formed microstructures were analysed and the porosity defects were quantified and discussed with regard to the heat input characteristics and the solidification conditions.

https://www.tandfonline.com/doi/pdf/10.1080/13621718.2018.1564986

Characterisation of 4043 aluminium alloy deposits obtained by wire and arc additive manufacturing using a Cold Metal Transfer process

Nowadays amongst additive manufacturing (AM) technologies, the Wire and Arc Additive Manufacturing (WAAM), process that uses metallic wire as filler and an arc welding process as a fusion source, is promising especially because of its high deposition rate, low cost raw materials, low material loss, and capability to manufacture large parts with an automatized system. On the other hand, the aluminum is a frequently used material in the industry, principally because its low density and mechanical properties, what make it interesting to be employed by AM processes. The present study focuses on the implementation of a Cold Metal Transfer (CMT) welding generator using an aluminum alloy wire (Al5Si) for AM applications. CMT process is a promising one for WAAM, thanks to its controlled current waveform and filler wire feeding that allow regular deposited weld beads. The aim of this work is to identify the relationships between the CMT welding parameters and the physical characteristics of deposited metal, in order to find the most suited parameters allowing a regular deposit. The CMT work parameters were evaluated in order to observe its effects on the morphological aspect of the deposited weld beads. Construction of multilayer metallic walls is achieved, and the presence of geometrical defects that could affect the correct wall formation was identified when the deposit is not continuous, with many ignition and stop cycles. Some propositions to decrease the presence of these defects are tested. Attempts of multi layers addition are presented, and relationship between these last results and CMT parameters is discussed.

https://hal.archives-ouvertes.fr/hal-01909063/document

Luis Corona Galvan

Papers

Characterisation of 4043 aluminium alloy deposits obtained by wire and arc additive manufacturing using a Cold Metal Transfer process

Effect of welding parameters on the quality of multilayer deposition of aluminum alloy