| 1. |
- Hauser, Tobias, et al.
(författare)
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Oxidation in wire arc additive manufacturing of aluminium alloys
- 2021
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 41
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Tidskriftsartikel (refereegranskat)abstract
- Wire Arc Additive Manufacturing is a near-net-shape machining technology that enables low-cost production of large and customised metal parts. In the present work, oxidation effects in Wire Arc Additive Manufacturing of the aluminium alloy AW4043/AlSi5(wt%) were investigated. Two main oxidation effects, the surface oxidation on aluminium parts and the oxidation anomalies in aluminium parts were observed and analysed. The surface oxidation on aluminium parts changed its colour during Wire Arc Additive Manufacturing from transparent to white. In the present work, it was shown by high-speed imaging that this change in the surface oxidation took place in the process zone, which was covered by inert gas. Since the white surface oxidation formed in an inert gas atmosphere, it was found that the arc interacts with the existing amorphous oxide layer of the previously deposited layer and turns it into a white duplex (crystalline and amorphous) oxide layer. In addition to the analysis of the white surface oxidation, oxidation anomalies, which occur at low shielding from the environment, were investigated. It was shown by physical experiments and Computational Fluid Dynamics simulations, that these oxidation anomalies occur at inadequate gas flow rates, too big nozzle-to-work distances, process modes with too high heat input, or too high wire feed rates. Finally, a monitoring method based on light emission spectroscopy was used to detect oxidation anomalies as they create peaks in the spectral emission when they occur.
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| 2. |
- Hauser, Tobias, et al.
(författare)
-
Porosity in wire arc additive manufacturing of aluminium alloys
- 2021
-
Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 41
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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