Positron annihilation studies of quenching and recovery of single crystals of Al and Al – 1.5 × 10−2 at.% Mn

Abstract

Single crystals of Al and Al – 1.5 × 10−2 at.% Mn have been quenched from 753 K. The quenched state and its recovery have been studied by positron annihilation. The Doppler-broadening technique was used and the results analyzed in terms of characteristic peak (S) and wing (W) parameters, chosen to emphasize annihilation with valence and core electrons, respectively. The prime effects of the Mn are to enhance both the quenched-in defect signal for S and the rise in S observed during the initial stages of vacancy recovery (180–250 K). In surprising contrast, the W data are remarkably similar for the two materials and show little sign of vacancy recovery below 240 K. At higher temperatures, the recovery data for S and W do appear to complement one another. The main recovery stage is centred at 300 K and a second, broad stage extends from ~370–480 K. The main vacancy recovery stages found here show a good correspondence with earlier resistivity and quenching data. Measurements of the temperature dependence of S and W in Al for both the well-annealed and quenched states are in reasonable accord with results from a previous investigation.