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Item type:Publication, Access status: with files , Ageing response of an Al-Mg-Mn-Sc-Zr alloy processed by laser metal deposition in thin-wall structuresThe use of aluminium alloys containing Sc and Zr in additive manufacturing (AM) provides new solutions for lightweight design. Representative thin-wall structured parts were additively fabricated with a commercially available Al-4.55Mg-0.51Mn-0.65Sc-0.30Zr alloy in Laser Metal Deposition (LMD) process. A bi-directional and a uni-directional scan strategy were applied and laser power from 500 W to 600 W was used. Nanohardness tests were conducted on specimens aged at 300 °C for up to 19 h to observe the ageing responses. Fine-grained microstructures with few micro-sized precipitates containing Sc- and Zr were found in the last track of every specimen. The area formed by the track-overlapping was the opposite, but an apparent hardening was observed only after the ageing. AM-processes with local remelting are facing the challenge to exert the potential strengthening effect of aluminium alloys containing Sc. The mushy state must be suppressed to prevent the waste of the expensive rare elements.Publicationtype: Journal ArticleScopus© Citations 17 48 165 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigations of laser clad, thermal sprayed and laser remelted AlSi20-coatings on magnesium alloy AZ31B under constant and cycling thermal loadMagnesium alloys need to be coated for applications exhibiting mechanical or chemical loads. Al-based coatings with Si reinforcements have proven to be a suitable coating choice to offer good wear and corrosion protection. Especially in the automotive and aviation industry, the demand for lightweight construction materials such as Mg alloys is permanently growing. In some of these applications, like engine components, in passenger cars or shell parts in jet engines, Mg parts might also be exposed to thermal shocks or elevated temperatures. Laser clad, thermal spray and laser remelted thermal spray coatings made of AlSi20 were generated on magnesium alloy AZ31B. In order to qualify these coatings for applications exhibiting thermal loads, samples were exposed to 190°C, 300°C and 400°C for time periods of 3h to 144h. Thermal shock testing was performed in a cycling heating (200 and 300°C) and cooling (27°C) with a cycle length of approx. 14s. Increasing temperature and increasing heat exposure time period led to increasing diffusion between the coating and the substrate with formation of brittle Mg2Si. This led to the formation of cracks and pores under thermal loading which consequently resulted in delamination of the coating. The laser remelted thermal spray coatings behaved similar to the as-sprayed coatings since the layers were not melted. The results show that the performance of the AlSi20 coatings depends strongly on the coating process.Publicationtype: Journal Article23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Post-processing of 3D-printed parts using femtosecond and picosecond laser radiation(SPIE, 2014-04); ; ; ; Additive manufacturing, also known as 3D-printing, is a near-net shape manufacturing approach, delivering part geometry that can be considerably affected by various process conditions, heat-induced distortions, solidified melt droplets, partially fused powders, and surface modifications induced by the manufacturing tool motion and processing strategy. High-repetition rate femtosecond and picosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to reduce the surface roughness while preserving the initial part geometry. We studied post-processing of 3D-shaped parts made of Nickel- and Titanium-base alloys by utilizing Selective Laser Melting (SLM) and Laser Metal Deposition (LMD) as additive manufacturing techniques. Process parameters such as the pulse energy, the number of layers and their spatial separation were varied. Surface processing in several layers was necessary to remove the excessive material, such as individual powder particles, and to reduce the average surface roughness from asdeposited 22-45 μm to a few microns. Due to the ultrafast laser-processing regime and the small heat-affected zone induced in materials, this novel integrated manufacturing approach can be used to post-process parts made of thermally and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision.Publicationtype: Conference Paper41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Femtosecond laser post-processing of metal parts produced by laser additive manufacturing(Laser Inst. of America, 2013-10-02); ; ; ; High-repetition rate femtosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to improve the surface finish. Processing of 3D-shaped parts made of titanium-and nickel-base alloys resulted in the reduction of the average surface roughness to a few microns. This approach can be used to post-process parts made of thermally and mechanically sensitive materials and to attain complex designed shapes with micrometer precision. Advantages and limitations of this novel post-processing technique are discussed.America.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Ultrafast laser-based post-processing of parts produced by additive manufacturingLaser Additive Manufacturing (LAM) is a near-net shape manufacturing approach, meaning that the resulting part geometry can be considerably affected by heat-induced distortions, solidified melt droplets, partially fused powders, and surface modifications induced by the laser tool motion and processing strategy. High-repetition rate femtosecond laser radiation was utilized to improve surface quality of metal parts manufactured by laser additive techniques. Different laser scanning approaches were utilized to increase the ablation efficiency and to improve the surface finish. Processing of 3D-shaped parts made of Ni- and Ti-base superalloys resulted in the reduction of the average surface roughness to a few microns. This approach can be used to post-process parts made of thermally and mechanically sensitive materials, and to attain complex designed shapes with micrometer precision.Publicationtype: Conference Paper17