Abstract
Hydronalium (aluminium-magnesium alloys) are characterized by high mechanical properties, excellent machinability, and good corrosion resistance. They are, however, among the most difficult alloys to cast because of their high drossing tendency when molten, of the sensitivity to impurities, hence much care is necessary to use magnesium ingot, return scrap, and even virzin aluminium ingot.
The mechanical properties and corrosion resistance of 5 per cent Hydronalium (aluminium-5 per cent magnesium alloy) are rather sensitive to small difference in the chemical composition. The authors discuss in the report the effect of the content of magnesium, manganese and iron on these properties. All the specimens were cast into the permanent mold.
The mechanical properties showed considerable unstability when magnesium is added more than 5 per cent and in case of 4.5 per cent magnesium elongation increases in spite of comparatively lower tensile strength. The hardness is improved as the content of maganese increases and iron does not make a much effect.
Corrosion test was made by submerging the specimens into 3 per cent sodium chloride aqueous solution, city water and rain water in statical state.
Corrosion resistance to sodium chloride aqueous solution was better with 4.6 per cent magnesium alloy than with 5 or 5.4 per cent magnesium alloys improvable to 5.0 or 5.4 per cent magnesium alloy. When submerged into city water, the less magnesium contents was, the less the weight change became. And their, compact film on the surface of the specimens seemed to introduce the good corrosion resistance.
