Annealing of cold worked hypostoichiometric Ni3Al alloys using positron lifetime spectroscopy

Hypostoichiometric Ni3Al alloys of composition 76.2 Ni:23.8 Al containing impurity levels of boron and hafnium were either cold rolled or pressed. Rolled and pressed samples were deformed by 20% and 10% thickness reductions, respectively. Samples were annealed isochronally at approximately 500C intervals up to 10500C. Two major annealing stages were apparent in all three alloys studied. These could be attributed to vacancy migration to sinks and annealing of dislocations and(or) recrystallization. The onset of vacancy migration occurred at approximately 2000C in all three alloys. Annealing of dislocations started at 6500C to 7000C and was complete at 10000C for alloys which contained boron and or hafnium impurities. In the pure alloy the onset of dislocation annealing occurred at 8000C and was incomplete at the highest (10500C) annealing temperatures reached