Positron annihilation lifetime (PAL) studies of the variations of microstructure during isochronal annealing of Cu-Zn (60/40) alloy

The microstructure variations during isochronal annealing of the as-received and quenched Cu-Zn (60/40) alloy were studied in the temperature range from room temperature range (RT)-1173 K. The experimental information was basically obtained by means of positron annihilation lifetime spectroscopy and Vickers microhardness. The microstructure was studied by optical and scanning electron microscopy observations. The Arrhenius plot of the data produced by the analysis of the positron annihilation spectra according to the simple trapping model is valid only at certain temperatures. Two regions were selected. The first region was at lower temperatures and its activation energy was 0.55±0.02 eV, which may be attributed to the energy of vacancy formation. The second region (at higher temperatures) was characterized by an activation energy (1.23±0.03 eV) that suggested it was related to the activation energy of recrystallization in the bulk material. The analysis of positron lifetime indicated clear evidence of the existence of three-dimensional defects in addition to one-dimensional defects, thus it needs a modification to the simple trapping model to consider the inhomogeneous trapping.