Effect of the degree of deformation on the structure and thermal stability of nanocrystalline niobium produced by high-pressure torsion

Попова, Е. Н.; Popov, V. V.; Романов, Е. П.; Pilyugin, V. P.

doi:10.1134/s0031918x0704014x

Cited by 47 publications

(30 citation statements)

References 3 publications

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“…1(e) that some relatively coarser grains appear in the edge area of the disc after processing by HPT through 10 turns. A similar result was also reported in the HPT processing of niobium [46] where it was assumed that the microstructure recovers at the expense of grain boundary migration [47]. There is also a possibility of texture-induced grain coalescence in which several grains of similar orientations come together so that the boundaries between them develop as new low-angle boundaries and the subsequent merging of the grains leads to the generation of a new coarser structure.…”

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confidence: 56%

A critical examination of pure tantalum processed by high-pressure torsion

Maury

Zhang

Huang

et al. 2015

Materials Science and Engineering: A

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Tantalum, a common refractory metal with body-centred cubic (BCC) crystalline structure, was processed by high-pressure torsion (HPT) at room temperature through different numbers of rotations. Significant grain refinement and high strength were achieved with a reduction in grain size from ~60 m to ~160 nm and an increase in strength from ~200 to >1300 MPa. Hardness measurements revealed a high level of homogeneity after 10 turns of HPT but the hardness after 10 turns was slightly lower than after 5 turns indicating the occurrence of some recovery. Tensile testing at a strain rate of 1.0  10 -3 s -1 gave high strengths of ~1200 MPa but little or no ductility after processing through 1, 5 and 10 turns.The introduction of a short-term (15 min) anneal immediately after HPT processing led to significant ductility in all samples and a reasonable level of strength at ~800 MPa.

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supporting

confidence: 56%

A critical examination of pure tantalum processed by high-pressure torsion

Maury

Zhang

Huang

et al. 2015

Materials Science and Engineering: A

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“…Although many reports are available for Fe, [10][11][12][13] very limited applications have been reported on the bcc metals using the HPT process. [14][15][16][17][18][19] In this research, two bcc metals, V and Mo, are selected because not only there are few studies using the HPT process but also there is a marked difference in the strength between V and Mo where V is softer and lower melting point (2136 K) but Mo is harder and higher melting point (2883 K).…”

Section: Introductionmentioning

confidence: 99%

Microstructures and Mechanical Properties of Pure V and Mo Processed by High-Pressure Torsion

2010

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Two body centered cubic (bcc) metals, V and Mo, were processed by high pressure torsion (HPT) at ambient temperature. Hardness variation as well as microstructural evolution was examined with strain under a pressure of 2 to 6 GPa. It was shown that the hardness increases with straining and saturates to a constant level with the grain size of 330-400 nm in V irrespective of the applied pressures. Although the hardness variation with strain is the same for Mo with the grain size of $350 nm at the saturation level when the applied pressure is 6 GPa, the hardness level lowers below the saturation level and the grain size becomes coarser as the pressure is lowered. Tensile tests show that the strength significantly increases with some ductility for V after processing under any pressure and for Mo under lower pressures, but brittle fracture occurs in the Mo specimen processed at 6 GPa. The slower evolution of microstructure as well as the lower hardness levels observed in Mo is due to the applied pressure which is lower than the yield stress and thus due to the insufficient generation of dislocations for grain refinement.

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“…The value obtained is about twice as high as of niobium nanostructured at room temperature [13] or of high-strength heavily-drawn Cu-Nb composites [25,26] in which anomalously high strength is due to nano-scaled sizes of Nb filaments and interspaces between them in copper matrix [27].…”

Section: Resultsmentioning

confidence: 86%

“…It becomes nanocrystalline throughout the specimen's cross-section, and both the average grain size (75 nm) and the grain size scattering (30-180 nm) are considerably lower than that attained at room temperature HPT [13,24]. It is interesting to note that in this case the structure is quite uniform along the specimen's radius.…”

Section: Resultsmentioning

confidence: 92%

“…As shown in [12,13], single-crystalline high-purity niobium subjected to HPT by 5 revolutions of anvils at room temperature acquires the structure which may be considered as borderline between the nano-and submicrocrystalline with crystallites sizes of 100-120 nm, high dislocation density and wide defective highangle boundaries. Besides, some areas of cellular structure are also retained in it after such treatment.…”

Section: Introductionmentioning

confidence: 99%

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