Application of positron annihilation spectroscopy to study the relationship between microstructure and metallurgical property of a commercial pure copper

The microstrueture variations of cold-rolled (80% reduction in thickness) commercial pure copper (99.5%) after isochronal annealing between room temperature (RT) and 1223 K were studied by using positron annihilation lifetime (PAL) microhardness measurements and optical and scanning electron microscopy (SEM) observations. The results indicate that the behavior of the short lifetime (T1) with the annealing temperature is nearly similar to the behavior of the microhardness measurements. The measured values of T1 were found to be higher than the bulk lifetime value at all temperatures except at the temperature interval 823-923 K. This could be attributed to recrystallization and grain growth in the copper. However, the trend of the intensity (I2) and the trapping rate (K) with annealing temperature are the same. The existence of two peaks for both I2 and K are probably due to the occurrence of two recrystallization stages.