Uphill quenching to reduce residual stress in a heat treatable aluminium alloy

Three rectilinear blocks of the aluminium alloy 7449 were characterised using neutron and X-ray diffraction. One block was heat treated normally and two blocks were subject to uphill quenching from −196°C to 100°C. Boiling water and steam were used to rapidly increase the temperature of the blocks to reverse the thermal gradients introduced by cold water quenching. It was possible to detect the beneficial influence of uphill quenching on residual stress using either fluid. The influence of steam was very effective but localised and limited to the surface in close proximity to the steam jet. For more uniform stress relief, multiple steam jets will be required to ensure the entire surface receives a significant thermal input.