Positron annihilation study on the effect of Si-content on the recovery of deformed cast Al-Si alloys

Isochronal annealing of Al-1100 and cast Al-Si alloys (Si-content 2, 4, 6 and 8 wt%) after deformation of 66% thickness reduction was investigated between room temperature (RT) and 500 °C. The annealing of defects was studied using Doppler Broadening Spectroscopy (DBS), Total Strain (εT) and Scanning Electron Microscope (SEM). It was found that; (i) three annealing stages of microstructure have been identified for Al-1100 and Al-Si alloys which are related to recovery, partial recrystallization and complete recrystallization (ii) the interaction between Si-precipitates and dislocations in Al-Si alloys leads to higher values of normalized line shape parameter (Snor) and lower values of εT than those for Al-1100 alloy also, it retarded the recovery and recrystallization with temperature (iii) the S-W plot revealed the presence of one type of defects in Al-1100 alloy but in Al-Si alloys the slope of the trajectory changes, which may indicate the occurrence of another defect type (Si-dislocation interaction) (iv) a negative correlation is observed between εT and Snor while a positive correlation between εT and normalized wing parameter (Wnor) is obvious.