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Spinodal ordering and precipitation in U-6wt%Nb

  • Luke Lieh-Ming Hsiung (a1) and Jikou Zhou (a2)

Abstract

A combinative approach of microhardness testing, tensile testing, and TEM microstructural analysis was employed to study the microstructure and mechanical instability of a water-quenched U-6wt.% Nb (WQ-U6Nb) alloy subjected to different aging schedules including artificial aging at 200°C, 15-year natural aging at ambient temperatures, and 15-year natural aging followed by accelerative aging at 200°C. The changes in mechanical property during and after the aging processes were examined using microhardness and tensile-testing methods. During the early stages of artificial aging at 200°C, the microhardness of WQ-U6Nb alloy increased, i.e., age hardening, as a result of the development of nanoscale modulation caused by spinodal decomposition. Coarsening of the modulated structure occurred after a prolonged aging at 200°C for 16 hours, and it led to a decrease of microhardness, i.e., age softening. Phase instability was also found to occur in WQ-U6Nb alloy that was subjected to a 15-year natural aging at ambient temperatures. The formation of partially ordered domains resulting from a spinodal modulation with an atomic-scale wavelength rendered the appearance of swirl-shape antiphase domain boundaries (APBs) observed in TEM images. Although it did not cause a significant change in microhardness, 15-year natural aging has dramatically affected the aging mechanisms of the alloy isothermally aged at 200°C. Microhardness values of the NA alloy continuously increased after isothermal aging at 200°C for 96 hours as a result of the phase decomposition of partially ordered domains into Nb-depleted α phase and Nb-enriched U3Nb ordered phase in the alloy. It is concluded that the long-term natural aging changes the transformation pathway of WQ-U6Nb, and it leads to order-disorder transformation and precipitation hardening of WQ-U6Nb alloy.

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1. Vandermeer, R.A., Acta Metall., 28 (1980), p. 383.10.1016/0001-6160(80)90173-X
2. Eckelmeyer, K.H., Romig, A.D., and Weirick, L.J., Met. Trans. A, 15A (1984), p. 1319.10.1007/BF02648560
3. Vandermeer, R.A., Ogle, J.C., and Northcutt, W.G. Jr, Met. Trans. A, 12A (1981), p. 733.10.1007/BF02648337
4. Field, R.D., Thoma, D.J., Dunn, P.S., Brown, D.W., Cady., C.M, Phil. Mag. A, 81 (2001), p. 1691.10.1080/01418610010010971
5. Jackson, R.J., Miley, D. V., Trans. ASM, 61 (1968), p. 336.
6. Beverini, G., Edmonds, D.V., Colloque De Physique, Colloque C8, C8429.
7. Cahn, J.W., Trans. TMS of AIME, 242 (1968), p. 166.
8. Sato, K. and Stobbs, W.M., Phil. Mag. A, 69 (1994), 349.10.1080/01418619408244349
9. Butler, E.P. and Thomas, G., Acta Metall., 18 (1970), 347.
10. Edington, J.W., Practical Electron Microscopy in Materials Science, Van Nostrand Reinhold, New York, 1976.

Keywords

Spinodal ordering and precipitation in U-6wt%Nb

  • Luke Lieh-Ming Hsiung (a1) and Jikou Zhou (a2)

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