The nature of point defects in plastically deformed aluminium

In order to find out which types of point defect are produced by plastic deformation, 57Co-doped aluminium specimens were cold worked at various tempera tures (4·2, 45, 55 and 80 K) by unidirectional tensile deformation or cyclic torsion. The specimens were then annealed at increasing temperatures, and the trapping of defects at the 57Co probes was studied by Mössbauer spectroscopy. In none of the experiments wore interstitials found, although it is known that in aluminium 57Co probes readily trap interstitialsaftor low-temperature particle irradiation. However, vacancy trapping was found in two temperature ranges corresponding to two different migration energies of vacancies: in dislocations E m d≃ 0·2 to 0·3eV and in the lattice E m≃ 0·6 eV. The consequences of the results on models of point defect production by cold working are discussed.