Reducing Hydrogen Pores and Blisters by Novel Strategies and Tailored Heat Treatments for Laser Powder Bed Fusion of AlSi7Mg0.6

摘要

AlSi7Mg0.6 produced by Laser Powder Bed Fusion can suffer from hydrogen pores. The root cause is a combination of the large hydrogen solubility in liquid aluminium and the hydrogen solubility gap during solidification. Moreover, applying conventional heat treatments (T4, T6, T7) cause severe hydrogen blistering and deteriorates the density and mechanical properties. This paper discusses novel LPBF processing strategies and tailored heat treatments to reduce significantly hydrogen porosity and blistering. The application of high scan speeds results in hydrogen solute trapping, thus avoiding hydrogen porosity. Three heat treatments are selected, resulting in a range of excellent mechanical properties of parts for which hydrogen blistering are avoided. Furthermore, a powder ageing study is performed on 3D Systems DMP Flex 350 LaserForm® AlSi7Mg0.6(A), showing that quality requirements are still met over a period of several months. The study shows that the atmospheric control of the DMP Flex 350 improves the powder ageing stability.