Estimation of the stored energy of dislocation for plastically deformed 6082 heat treatable Al-Alloy

Abstract

This work describes cold work effect on the positron annihilation parameters, which are used in determination of the stored dislocation energy of the investigated 6082 Al-alloy samples. The investigated samples were homogenized for 6 h at 723 K then annealed at room temperature and finally plastically deformed up to 23 % degree of deformation. The annihilation parameters of the alloys under investigation were determined using the trapping model after fitting with the experimental measured data of the positron annihilation lifetime. 12% thickness reduction was found to be the start of saturation trapping region of positron in defect states at which an annihilation lifetime value of about 209±4 ps is obtained.A trapping efficiency of 6×10-7 cm3s-1 gives the best fit of the experimental measurements with the theoretical mean lifetime values obtained using the trapping model. The stored dislocation energy can be determined from the data of the positron annihilation lifetime due its ability to determine the density dislocation during plastic deformation. An increase in the strain (degree of deformation) creates comparable increase in both defect and dislocation densities, hence an increase in the measured stored dislocation energy. Maximum stored dislocation energy of about 29.5 KJ/m3 was obtained at the region of saturation of dislocation.