| Popis: |
The ordered face-centered cubic (fcc) zirconium-aluminum phase (Zr 3 Al, Ll 2 type) is being evaluated as a future CANada Deuterium Uranium (CANDU) reactor pressure-tube material on the hypothesis that ordering may lead toa reduction in rates of atomic diffusion and dislocation climb, and, hence, to a reduction of in-reactor creep. Experiments have been performed to measure the effects of fast neutrons on the dimensional stability, tensile properties, and corrosion resistance, in addition to measuring the in-reactor creep rates of a Zr-8.6Al alloy. Irradiation-induced dimensional changes (in the absence of an applied stress) occurred which differed significantly in nature from those of Zircaloy and Zr-2.5Nb. The changes appear to have been caused by a combination of growth and swelling and decrease with increasing temperature; the dimensional changes appear to level off at 0.3 percent after 2 x 10 2 4 neutrons (n)/m 2 at 600 K. The long-term creep resistance at 570 K, deduced from bent-beam stress relaxation, is expected to be better than that of Zr-2.5Nb provided that the dimensional change does in fact level off. The tensile strength and ductility are superior to those of Zr-2.5Nb, while the resistance to aqueous corrosion is as good, provided that the α-zirconium phase content is ≤ 1 percent by volume. |
