Hydrogen in aluminium die castings - Formation of hydrides and their effects on base material, heat treatability and weldability

The alloys AB-Al Si9Mg (Silafont 36), AB-Al Mg5Si2Mn (Magsimal 59), AB-AI M g2.5Mn (Magsimal 22), AB-Al Si11Mg (Calypso 61D), AB-AI Si9 (Calypso 49R) a nd AB-AlSi8Cu3 (226) were investigated to examine the influence of hydride forming elements on base material, heat treatability and weldability. Exper iments with the alloys AB-AI Si11Mg and AB-AI Si8Cu3 with a higher titanium content completed the investigations. The determination of concentration-p ressure isotherms on die castings of the alloy AB-AI Si8Cu3 shows a capacit y for absorption of hydrogen up to one weight percent. This high factor pro ves again the chemical binding of hydrogen in aluminium die casting alloys. The tensile strength and elongation of not heat treated die castings were independent of the hydrogen contents. The results show an improvement of th e heat treatability and a deterioration of the weldability when the content s of hydride forming elements in the aluminium alloy become higher.