SIMULATION OF MICROSTRUCTURE AND LIQUATION CRACKING IN 7017-ALUMINUM-ALLOY

Welding in a 7000 series aluminium alloy can lead to the development o f a white zone microstructure and liquation cracking in the heat affec ted zone adjacent to the fusion boundary. A Gleeble 1500 thermomechani cal system has been used to study the conditions associated with damag e development. A range of simulations has been carried out covering th ermal and thermomechanical conditions typically encountered during wel d manufacture. Results show that both the white zone microstructure an d liquation cracking can be simulated at a sufficient scale to permit full characterisation in laboratory testpieces. Data analysis has defi ned and mapped the stress and temperature conditions leading to crack initiation. This evaluation demonstrates that the susceptibility for c racking is minimised by increasing the cooling rate following weld man ufacture.