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 X lo-' 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.