Laser Remelting for Reduced Porosity on Additively Manufactured Aluminium Mirrors

Laser Remelting for Reduced Porosity on Additively Manufactured Aluminium Mirrors
Joshua West (STFC – UK Astronomy Technology Centre), Valentina Oyarzun (STFC – UK Astronomy Technology Centre), Marcell Westsik (STFC – UK Astronomy Technology Centre), Younes Chahid (STFC – UK Astronomy Technology Centre), Magdalena Kraus (STFC – UK Astronomy Technology Centre), Scott McPhee (STFC – UK Astronomy Technology Centre), William Brzozowski (STFC – UK Astronomy Technology Centre), Samuel Tammas-Williams (School of Engineering, University of Edinburgh), Nicola Cayzer (School of Geoscience, University of Edinburgh), Fraser Laidlaw (Physics and Astronomy, University of Edinburgh), Sameer Dayanand Meshram (Department of Mechanical Engineering, KU Leuven), Daniel Ordnung (Department of Mechanical Engineering, KU Leuven), Berk Baris Celik (Department of Mechanical Engineering, KU Leuven), Michel Smet (Department of Mechanical Engineering, KU Leuven), Mirko Sinico (Department of Mechanical Engineering, KU Leuven), Wenjuan Sun (Department of Mechanical Engineering, KU Leuven), Brecht Van Hooreweder (Department of Mechanical Engineering, KU Leuven), Michael Harris (STFC – Central Laser Facility Engineering and Technology Centre), Stephen James (STFC – Central Laser Facility Engineering and Technology Centre), Carolyn Atkins (STFC – UK Astronomy Technology Centre)
arXiv:2607.21253v1 Announce Type: cross
Abstract: Additively manufactured (AM) AlSi10Mg mirrors are fabricated through laser powder bed fusion (LPBF), allowing the use of complex geometries such as lattices and organic structures that enable high mass reduction while maintaining mechanical stiffness. Micron-sized pores that cause optical scatter may form during LPBF as a consequence of deviations from the optimal processing window, particularly from laser energy input and scan strategy. This work proposes a laser remelting strategy aimed at reducing porosity; standard LPBF build steps automatically alternate with laser remelting passes, where previously deposited material is remelted during fabrication.
Laser remelting is evaluated through fabricating 10 mm proof-of-concept cubes. Following single point diamond turning (SPDT), optical measurements characterised surface roughness and identified surface artefacts. The best-performing AlSi10Mg remelted cube exhibited no pores within sampled regions and achieved 6.4 nm average surface roughness, comparable to a conventionally manufactured RSA 6061 control cube (5.8 nm). Driven by these results, AM 52 mm diameter secondary sandwich mirrors were manufactured using LPBF and laser remelting. These incorporate an optimised diamond TPMS lattice to achieve a 50% mass reduction while accommodating design for AM considerations. Unlike the cube study, the optical surface of the remelted mirror after SPDT exhibited residual porosity and 11.8 nm average surface roughness. These results show that while the proof-of-concept confirmed the viability of laser remelting in reducing porosity within simple geometries, optimisation of the LPBF and SPDT processes are required to translate the benefits of laser remelting to lightweight AlSi10Mg AM mirrors.arXiv:2607.21253v1 Announce Type: cross
Abstract: Additively manufactured (AM) AlSi10Mg mirrors are fabricated through laser powder bed fusion (LPBF), allowing the use of complex geometries such as lattices and organic structures that enable high mass reduction while maintaining mechanical stiffness. Micron-sized pores that cause optical scatter may form during LPBF as a consequence of deviations from the optimal processing window, particularly from laser energy input and scan strategy. This work proposes a laser remelting strategy aimed at reducing porosity; standard LPBF build steps automatically alternate with laser remelting passes, where previously deposited material is remelted during fabrication.
Laser remelting is evaluated through fabricating 10 mm proof-of-concept cubes. Following single point diamond turning (SPDT), optical measurements characterised surface roughness and identified surface artefacts. The best-performing AlSi10Mg remelted cube exhibited no pores within sampled regions and achieved 6.4 nm average surface roughness, comparable to a conventionally manufactured RSA 6061 control cube (5.8 nm). Driven by these results, AM 52 mm diameter secondary sandwich mirrors were manufactured using LPBF and laser remelting. These incorporate an optimised diamond TPMS lattice to achieve a 50% mass reduction while accommodating design for AM considerations. Unlike the cube study, the optical surface of the remelted mirror after SPDT exhibited residual porosity and 11.8 nm average surface roughness. These results show that while the proof-of-concept confirmed the viability of laser remelting in reducing porosity within simple geometries, optimisation of the LPBF and SPDT processes are required to translate the benefits of laser remelting to lightweight AlSi10Mg AM mirrors.