Zr Single Crystals Research Articles

Irradiation creep in Zr single crystals

A single crystal of crystal bar Zr was irradiated, unstressed, at 570 K in a fast (> 1 MeV) neutron flux of 5.5 × 10 16 n/m 2-s . After a dose of 6 × 10 23 n/m 2 a tensile stress of 25 MPa was applied during a period of steady reactor power. The loading strain was an order of magnitude smaller than that observed when an identical, unirradiated, crystal was loaded to the same stress. There followed a period of primary creep during which the creep rate decreased to a value of 5 × 10 −6 h −1 in the first 24 hours of the test. For the final 2000 hours of the test the specimen was observed to creep at a rate of 1 × 10 −6 h −1 when the reactor was at full power. During shutdowns, the creep rate decreased with time. The results will be discussed and compared with predictions from current theories for the mechanism of irradiation enhanced creep in light of the micro-structures observed.

Magnetic Moment of ZrZn2up to 150 kG: is "Pure" ZrZn2Ferromagnetic?

We present magnetic-moment measurements in polycrystalline and single-crystal Zr${\mathrm{Zn}}_{2}$ for fields to 150 kG. The high-field susceptibility is identical for all materials whereas the low-field moment varies over a wide range. The data indicate that the low-field moment is correlated with trace impurities (such as Fe and Ti) and details of preparation. We suggest a localized-moment model for ferromagnetism in impure Zr${\mathrm{Zn}}_{2}$ which is consistent with our results; but it is not yet clear whether or not "pure" Zr${\mathrm{Zn}}_{2}$ is ferromagnetic.