Effect of precipitation during quenching on the mechanical properties of the aluminium alloy 7010 in the W-temper

Residual stress magnitudes in quenched high-strength aluminium alloys determined by several researchers using a variety of techniques indicate values that far exceed the as measured yield strength of the material in the quenched condition. Some research has indicated that the high residual stress magnitudes in large forgings may partly occur as a result of precipitation during the quench. To investigate this theory, a novel Jominy end quench technique is used to determine the hardness of aluminium alloy 7010 as a function of cooling rate. Cooling curves have been measured for Jominy end quench type samples using deeply buried thermocouples and are compared with finite element model predictions. Tensile properties are also determined for samples quenched into boiling water and compared with samples quenched into cold water. Vickers hardness and X-ray diffraction residual stress measurements are undertaken on samples of varying size acting as a comparison with the Jominy results to indicate how both homogenous and heterogeneous precipitation lead to increased as quenched mechanical strengths. (C) 2004 Elsevier B.V. All rights reserved.