A phenomenological study of the shape memory effect in polycrystalline uranium-niobium alloys

Vandermeer, R.A.; Ogle, Jonathan; Northcutt, W.G.

doi:10.1007/bf02648337

Cited by 75 publications

(56 citation statements)

References 17 publications

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“…These values were based on data for U-6Nb and U-8Nb [5]. The material used by Vandermeer, et al [1][2][3][4] was chosen as the second pedigree. Only the initial yield strength was modified (c 1 = 0.640 GPa) relative to the baseline parameters in Table I for the second material.…”

Section: Resultsmentioning

confidence: 99%

“…Only the initial yield strength was modified (c 1 = 0.640 GPa) relative to the baseline parameters in Table I for the second material. The phase transformation start (M s ) and finish (M f ) temperatures were obtained from Vandermeer, et al [1][2][3][4]. Additional data are being pursued to define better the necessary material properties.…”

Section: Resultsmentioning

confidence: 99%

“…Uranium-niobium (U-Nb) alloys within the range from 5 weight percent (U-5Nb) to 8 weight percent (U-8Nb) of niobium exhibit the shape memory effect [1][2][3][4][5]. A phase diagram for U-Nb alloys in the vicinity of the monotectoid composition (U-6Nb) is provided in Fig.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Model for High-Strain-Rate Deformation of Uranium-Niobium Alloys

Addessio¹,

Zuo²,

Mason³

et al. 2003

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A Model for High-Strain-Rate Deformation of Uranium-Niobium Alloys

Addessio¹,

Zuo²,

Mason³

et al. 2003

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“…The WQ-U6Nb alloy has improved mechanical properties (ductility and toughness) [2,3] and excellent corrosion resistance [4,5] because of the uniform distribution of niobium atoms in the solid solution that suppresses the diffusional decomposition reaction to form a two-phase (a Nb-depleted α phase and a Nbenriched γ phase) cellular microstructure. It has also been demonstrated that the water-quenched WQ-U6Nb alloy containing α′′ martensite reveals shape memory effect [6,7].…”

Section: Introductionmentioning

confidence: 97%

Microstructure and Mechanical Instability of Water-Quenched U-6wt% Nb Alloy Affected by Long-Term Aging

Hsiung¹,

Zhou²

2005

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Objectives and accomplishmentsA combinative approach of microhardness testing, tensile testing, and TEM microstructural analysis was employed to study the microstructure and mechanical instability of a waterquenched 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 and no age softening was found 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 U 3 Nb 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, precipitation hardening, and ductility embrittlement of WQ-U6Nb alloy.

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“…It has also been demonstrated that the U-Nb alloy containing α′′ martensite reveals shape memory effect [3], and the shape memory behavior is controlled mainly by the twin structures within the alloy [4]. Aging of the α′′ martensite in the 150°C to 400°C range results in an increase of yield strength to as high as 1.3 GPa due to very fine scale microstructural changes [5], which have not yet been fully characterized but may have involved spinodal decomposition.…”

Section: Introductionmentioning

confidence: 99%

Spinodal ordering and precipitation in U-6wt%Nb

Hsiung

Zhou

2005

MRS Proc.

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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 (WQU6Nb) 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 Nbenriched U 3 Nb 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.

show abstract

A phenomenological study of the shape memory effect in polycrystalline uranium-niobium alloys

Cited by 75 publications

References 17 publications

A Model for High-Strain-Rate Deformation of Uranium-Niobium Alloys

A Model for High-Strain-Rate Deformation of Uranium-Niobium Alloys

Microstructure and Mechanical Instability of Water-Quenched U-6wt% Nb Alloy Affected by Long-Term Aging

Spinodal ordering and precipitation in U-6wt%Nb

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