Effect of pre-stretching on the mechanical behaviour of three artificially aged 6xxx series aluminium alloys
Henrik Granum, Ole Runar Myhr, Tore Børvik, Odd Sture Hopperstad
Abstract
The effect of pre-stretching on the mechanical behaviour of the aluminium alloys AA6063, AA6061 and AA6110 in temper T6 has been investigated. Uniaxial tensile tests and quasi-static axial crushing tests were conducted on rectangular hollow section (RHS) profiles pre-stretched 0.5 % and 4.0 % prior to artificial ageing. The stress-strain curves from the uniaxial tensile tests with different pre-stretching levels were used to investigate the effect of pre-stretching on the mechanical behaviour. It was found that the yield stress and ultimate tensile stress were somewhat lower and the failure strain was considerably higher for the profiles pre-stretched 4.0 % compared to those pre-stretched 0.5 %. In the crushing tests, less cracks were generally seen by visual inspection on the profiles pre-stretched 4.0 % but the specific energy absorption was slightly lower for these profiles. The nanostructure model NaMo was used to predict the stress-strain curves and the results were compared to the experimental data. Overall, the experimental trends were accurately predicted by NaMo, even though the hardening stagnation observed predominantly for profiles pre-stretched 4.0 % was not captured. The predicted evolution of the microstructure during artificial ageing was used to gain insight into the physical mechanisms responsible for the observed stress-strain behaviour.