Stored Energy of Dislocations in Deformed 8006 AL Alloy by Positron Annihilation Lifetime Technique

This work describes the usage of positron annihilation lifetime technique (PALT) in determining the stored energy in 8006 Al alloy samples during plastic deformation performed by hydraulic press at room temperature (RT).The 8006 Al alloy is more and more used for manufacturing sheets and foils. Samples were homogenized at 773.0 K for 10 h then annealed to reach RT. The spectra of lifetime of positron are measured for samples with various degree of plastic deformation up to 48.30 %. It is known that at plastic deformation type of dislocation defects are generated basically. The concentration of dislocations with thickness reduction could be received and used to determine the stored energy which was found as a function of the thickness reduction. The variation of the stored energy with the thickness reduction seems to be an exponential growth from 0.59 KJ/m3 at 1.80 % to 49.00 KJ/m3 at 15.30 % thickness reduction related to the increasing of the dislocation density as predicted theoretically.