Influencing the hydrogen porosity in aluminium casting by (re)active filter materialsWednesday (07.10.2020) 14:20 - 14:40
Within the DFG-funded CRC 920 “Multi-Functional Filters for Metal Melt Filtration”, the effect of active and reactive filter materials in the filtration for the purification of molten metal is investigated. In this context, the influence of different filter materials on the hydrogen porosity of aluminium castings is explored.
For this purpose, an AlSi7Mg alloy was casted into a special steel mould, which makes it possible to form the hydrogen, which is released during solidification within the mould, completely as porosity in the casting. Various filter materials (e.g. Al2O3, LiAl(Si2O6), Al2O3-C, TiO2) were used to test their effect on the hydrogen precipitation. To quantify the amount of precipitated hydrogen, the castings are sliced, polished and the size of the pores formed is determined by automatic image analysis. In addition, the used filters are examined for possible interactions with the aluminium melt.
It has been found that filtration can influence hydrogen porosity positively and thus lead to a denser casting. The influence of the filter materials regarding their chemistry and surface roughness is worked out.