Microstructure and mechanical properties of CuxNb1−x alloys prepared by ball milling and high pressure torsion compacting

Abad, M.D.; Parker, Stephen S.; Kiener, Daniel; Primorac, Mladen-Mateo; Hosemann, Peter

doi:10.1016/j.jallcom.2014.11.193

Cited by 25 publications

(22 citation statements)

References 50 publications

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“…Even after annealing at 900 • C for 3 h, the size of the Nb nanoparticles is still 5-20 nm, and the structure of the Cu matrix remains nanocrystalline with grain size below 100 nm. The slow growth of the nanocrystalline Cu grains is in agreement with the results reported by other investigators [13,16,18,19]. Nevertheless, E. Botcharova et al demonstrated that a fast coarsening of the Nb particles led to a size of 150-350 nm at 900 • C for 1 h, and suggested that the sub-micron sized Nb particles could not hinder the Cu grain growth due to their much larger size than that of Cu grains [13,18,23].…”

Section: Discussionsupporting

confidence: 91%

Microstructure, Hardness Evolution, and Thermal Stability Mechanism of Mechanical Alloyed Cu-Nb Alloy during Heat Treatment

Lei

Wang

et al. 2016

Metals

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Abstract:The microstructure, hardness evolution, and thermal stability of mechanically alloyed (MA-ed) nanocrystalline Cu-10 wt %Nb solid solution during heat treatment were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) observations, and microhardness measurement. It is found that the pronounced precipitation of Nb from the Cu-Nb supersaturated solid solution occurs at temperatures up to 700 • C, and the annealed alloy shows a bi-nanostructure with Nb nanoparticles dispersed in the nanocrystalline Cu matrix. The bi-nanostructure remains stable with Cu crystalline grain size below 100 nm and Nb particle size around 10 nm even after annealing at 900 • C for 3 h. The microhardness of the annealed sample shows a small increase after annealing at 400 • C, and then it shows a slow decreasing trend with further increasing temperatures. With the help of the kinetics analyses, it is found that the coarsening of the stable Nb nanoparticles is controlled by volume diffusion. The enhanced stability of the nanocrystalline Cu microstructure is mainly attributed to the solute drag and precipitate pinning effects.

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Section: Discussionsupporting

confidence: 91%

Microstructure, Hardness Evolution, and Thermal Stability Mechanism of Mechanical Alloyed Cu-Nb Alloy during Heat Treatment

Lei

Wang

et al. 2016

Metals

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“…Although the ball-milled powders have grain sizes in the range of 10-20 nm, grain growth during sintering is rapid and the densified compacts have grain diameters of several microns [3,11,13]. Complete densification remains unachievable and intergrannular porosity is still observed after sintering [3,13].High pressure torsion (HPT) has been used for grain refinement and mechanically alloying of a wide range of Cu-based systems including Cu-Fe [15][16][17], Cu-Cr [18,19], Cu-Nb [20,21] and Cu-W [22,23]. Deformation is carried out under quasi-hydrostatic conditions, allowing brittle materials such as refractory metals to be extensively strained without the need for external heating.…”

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confidence: 99%

On nanostructured molybdenum–copper composites produced by high-pressure torsion

et al. 2017

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Nanostructured molybdenum-copper composites have been produced through severe plastic deformation of liquid-metal infiltrated Cu30Mo70 and Cu50Mo50 (wt%) starting materials. Processing was carried out using highpressure torsion at room temperature with no subsequent sintering treatment, producing a porosity-free, ultrafine-grained composite. Extensive deformation of the Cu50Mo50 composite via two-step high-pressure torsion produced equiaxed nanoscale grains of Mo and Cu with a grain size of 10-15 nm. Identical treatment of Cu30Mo70 produced a ultrafine, lamellar structure, comprised of Cu and Mo layers with thicknesses of $ 5 and $ 10À20 nm, respectively, and an interlamellar spacing of 9 nm. This microstructure differs substantially from that of HPT-deformed Cu-Cr and Cu-W composites, in which the lamellar microstructure breaks down at high strains. The ultrafinegrained structure and absence of porosity resulted in composites with Vickers hardness values of 600 for Cu30Mo70 and 475 for Cu50Mo50. The ability to produce Cu30Mo70 nanocomposites with a combination of high-strength, and a fine, oriented microstructure should be of interest for thermoelectric applications.

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“…The Cu–Nb system is classified as strongly segregating because of the large atomic size of Nb compared to Cu and the immiscibility of Nb in Cu with a positive heat of mixing, Δ H mix = 3 KJ mol −1 . This system was studied extensively by researchers and showed good thermal stability . However, to the best of our knowledge, no report in these previous studies attributed the enhanced thermal stability of Cu solely to the added pure solute atom (Nb).…”

Section: Introductionmentioning

confidence: 99%

“…That is primarily because in these studies the Cu–Nb alloys were prepared using a two‐step process of mechanical milling and subsequent consolidation and/or annealing at high temperatures. Using this two‐step process always incorporated contaminations from other elements (e.g., O, N, Fe, Cr, C). These elements were found to form different precipitates, such as NbO, CuO, Fe 7 Nb 6 , which acted to pin the grain boundaries and kinetically stabilize the nanostructure.…”

Section: Introductionmentioning

confidence: 99%

Influence of 1%Nb Solute Addition on the Thermal Stability of In Situ Consolidated Nanocrystalline Cu

Abaza¹,

Al‐Sulaiti²,

Scattergood³

et al. 2019

Adv Eng Mater

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Nanocrystalline (nc) Cu and Cu-1% Nb bulk materials are synthesized using a combination of cryogenic and room temperature ball milling. The grain size values of these in situ consolidated Cu and Cu-1% Nb, determined using transmission electron microscopy, are found to be 22 nm and 18 nm, respectively. In this investigation, isochronal heat treatments are performed for 1 h to establish grain size and microstructural changes as a function of temperature. The annealing of nc Cu-1% Nb at a temperature of 1073 K reveals a slight increase in the average grain size from 18 to 45 nm. The grain size of nc Cu, however, increases from 22 nm to about 3 μm after annealing at the same conditions. The present results indicate that solute entrapment plays a major role in thermal stability of the high purity contaminant-free Cu with the addition of only 1 at% Nb after annealing for 1 h up to a homologous temperature of 0.8. Kinetic stabilization via clustering of Nb atoms on the grain boundaries and the triple junctions is also observed after annealing at high temperature for longer times.

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Microstructure and mechanical properties of CuxNb1−x alloys prepared by ball milling and high pressure torsion compacting

Cited by 25 publications

References 50 publications

Microstructure, Hardness Evolution, and Thermal Stability Mechanism of Mechanical Alloyed Cu-Nb Alloy during Heat Treatment

Microstructure, Hardness Evolution, and Thermal Stability Mechanism of Mechanical Alloyed Cu-Nb Alloy during Heat Treatment

On nanostructured molybdenum–copper composites produced by high-pressure torsion

Influence of 1%Nb Solute Addition on the Thermal Stability of In Situ Consolidated Nanocrystalline Cu

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