Residual stress development and relief in high strength aluminium alloys using standard and retrogression thermal treatments

Residual stresses develop in the aluminium alloy 7010 when the material is quenched from the solution heat treatment temperature. Residual stress measurements have been made using the X-ray diffraction technique and a longitudinal split sawcut method to determine the magnitude of residual stress that develops in specimens sectioned from large open die forgings as a result of (a) quenching these specimens into water at different temperatures, and (b) cold water quenching from different furnace temperatures. Residual stress reductions as a result of retrogression and reaging and standard thermal treatments have been determined. The longitudinal split sawcut technique is used to demonstrate the viability of a cheap, rapid technique for determining surface stress magnitudes in specimens of suitable geometry. The variation in room temperature tensile properties of 7010 with natural aging time has also been determined. The surface residual stress magnitudes can significantly exceed the as quenched materials uniaxial limit of proportionality.