MECHANICAL-PROPERTIES AND MICROSTRUCTURE OF NEUTRON-IRRADIATED COLD-WORKED AL-6063 ALLOY

The impact of neutron irradiation on the mechanical properties and fra cture morphology of cold worked Al-6063 were studied, using scanning a nd transmission electron microscopy, and tensile measurements. Specime ns (50 mm long and 6 mm wide gauge sections) were punched out from an Al-6063 23% cold worked tubes, which had been exposed to prolonged neu tron irradiation of up to 4.5 x 10(25) thermal neutrons/m(2) (E < 0.62 5 eV). The temperature ranged between 41 and 52 degrees C. The tensile specimens were then tensioned till fracture in an Instron tensiometer with strain rate of 2 x 10(-3) s(-1). The uniform elongation and the ultimate tensile strength increase as functions of fluence. Metallogra phic examination and fractography reveal a decrease in the local area reduction of the final fracture necking. This reduction is accompanied with a morphology transition from ductile transgranular shear rupture to a combination of transgranular shear with intergranular dimpled ru pture. The intergranular rupture area increases with fluence. No voids could be observed up to the maximum fluence. The dislocation density of cold worked Al decreases with the thermal neutron fluence. Prolonge d annealing of unirradiated cold worked Al-6063 at 52 degrees C reveal ed similar results. It thus appears that under our irradiation conditi ons the temperature during irradiation is the major factor influencing the mechanical properties and the microstructure during irradiation. (C) 1998 Elsevier Science B.V.