Effect of filler materials on the tensile properties and fracture toughness of laser beam welded AA2198 joints under different ageing conditions

Abstract

The influence of different filler materials on the microstructure, tensile mechanical properties, and fracture toughness of laser beam welded AA2198 alloy as well as the effect of different artificial ageing heat treatments were investigated in this contribution. The welded joints were produced when exploited either, Al-Si (AA4047) or Al-Cu (AA2319) filler wires. It was shown that the Al-Si filler wire gave higher hardness values in the fusion zone when compared to the Al-Cu filler wire. The post heat treatment of the welded specimens increased by approximately +100 % the yield stress and by +20 % the ultimate tensile strength with increasing ageing time, in a similar way to the non-welded material. Elongation at fracture decreased in an inverse proportional manner to yield stress. Artificial ageing before welding gave improved elongation at fracture for the over-aged condition only. The quality index concept showed that the artificial ageing before the welding did not succeed in giving a higher quality of the welded joints, for both filler materials investigated. The opposite was shown on the post heat treatment, where the peak-aged condition increased substantially the ‘quality’ of the welded joints with both filler materials. The critical stress intensity factor was increased by +25 % for the under-aged condition for the post-welded condition and both investigated filler wires as a result of the balance between medium values in strength and ductility, respectively.