Behaviour of Artificial Aging in 6066 Alloy Using Microhardness and Nuclear Techniques
Many Aluminum-based alloys are strengthened by using a heat-treatment process known as age-hardening. The aim of this work was to produce a high-strength 6xxx-series Aluminum alloy by adjusting the processing conditions, namely solutionizing and artificial aging. It consists of heating the alloy to a temperature at which the soluble constituents will form an homogeneous mass via solid diffusion, holding the mass at that temperature until diffusion takes place, then quenching the alloy rapidly to retain the homogeneous condition. In the quenched condition, heat-treated alloys are supersaturated solid solutions that are comparatively soft and workable, and unstable, depending upon the composition. After solution treatment and quenching, hardening is achieved either at room temperature (natural aging) or via a precipitation heat treatment at a suitable temperature (artificial aging). Precipitation heat treatments are generally low-temperature, long-term processes. Temperatures range from 115 to 190C; times vary from 5 to 48 h. The choice of time-temperature cycles for precipitation heat treatment should receive careful consideration. The objective is to select the cycle that produces an optimum precipitate size and distribution pattern. The mechanical characterization of heat-treatable 6xxx (Al-Mg-Si-Cu based) 6066 wrought aluminum alloys was studied. Their effects were investigated in terms of microstructure using positron annihilation lifetime techniques and monitoring the mechanical properties by mean of Vickers hardness measurements. The hardness is the resistance of a material to plastic deformation, and gives it the ability to resist deformation when a load is applied. The greater the hardness of the material, the greater resistance it has to deformation. The Vickers hardness of 6066 alloy has its maximum value (98) when aged for (10) hours at (175C) after quenching at 530C; so this temperature is the solution temperature of this alloy .The hardness conformed to reference values.
David J. Fisher
E. A. Badawi et al., "Behaviour of Artificial Aging in 6066 Alloy Using Microhardness and Nuclear Techniques", Defect and Diffusion Forum, Vols. 305-306, pp. 15-22, 2010