Gamma-Irradiation Damage in Age Hardening Al Alloys
NOTRE DAME UNIV IN DEPT OF METALLURGICAL ENGINEERING AND MATERIALS SCIENCE
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Pure Al and a series of age-hardenable Al alloys have been gamma- irradiated in a Co60 source at a dose of 6000 radsmin. Internal friction measurements have been made at 80 kHz by means of the Marx technique on samples in situ during irradiation. In Al and Al-3 wo Cu, the damping decreases monotonically as is expected. The decrease is attributed to the immobilization of dislocations by the radiation-induced point defect pinners. In 2024-T6, 2017-T6 and A1-9.5 Mg, the damping passes through a minimum and begins an anomolous increase after 4 to 7 hours of irradiation. In the alloys which display the damping minimum, precipitate morphology changes during irradiation, with coarsening andor de-coarsening and re-nucleation being observed. The effect appears to depend upon the presence of Mg. Theory predicts that morphology changes can occur during gamma-irradiation, with the mechanism being either Rutherford collision or Coulombic repulsion radiation damage.
- Properties of Metals and Alloys