Microstructure and mechanical behavior of ultrafine-grained Ni processed by different powder metallurgy methods

Gubicza, Jenő; Bui, H. Q.; Fellah, F.; Dirras, G.

doi:10.1557/jmr.2009.0010

Cited by 36 publications

(37 citation statements)

References 32 publications

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“…[4,10] The UFG grains in bi-modal materials are known to promote a high strength by limiting dislocation movement, whereas the micron-sized grains occupy a larger proportion of the microstructure on a volumetric basis, thus increasing their effect on the behavior of the aggregate, such as ductility, by suppressing crack growth and facilitating plastic deformation. [4] Although a large amount of published work has qualitatively verified that the introduction of multi-scale grain structures can indeed improve the poor ductility of UFG materials, [11][12][13][14][15][16][17][18][19][20][21][22] this approach represents in fact, a compromise strategy: i.e., to achieve ductility by sacrificing strength. The question is what is the extent of such a compromise?…”

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confidence: 99%

Strength and Ductility of Bi‐Modal Cu

et al. 2011

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Engineering a microstructure with multiple length scales has been proposed as a strategy to enhance the plasticity of nanostructured materials which otherwise lack extensive dislocation activity, and therefore low ductility. To that effect, various research groups have implemented this concept by promoting the formation of so called bi‐modal microstructures (e.g., consisting of a mixture of ultrafine and micro‐grains) with balanced combinations of strength and ductility. Despite encouraging results, fundamental, information on important questions remained unanswered. For example, what is the relationship between the volume fraction of the coarse grained phase and the overall ductility? What is the influence of size of the coarse grained phase, and how does its distribution influence ductility? To provide insight into these, and other related questions, in this work, we prepared bimodal Cu with homogeneous distribution of different‐volume‐fraction micro‐grains via isothermal recrystallization of an ultrafine grained Cu matrix at 200 °C. Analysis of the tensile results and microstructural characterization suggest that both strength and ductility of the bi‐modal Cu follows the rule‐of‐mixtures, with interesting results related to volume fraction. Our work provides a pathway for optimizing the mechanical properties of multiscale materials.

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Strength and Ductility of Bi‐Modal Cu

et al. 2011

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“…X-ray diraction and energy-ltered TEM investigations revealed that there is a native crystalline NiO layer on the surface of Ni powder particles [38]. In the sintered materials this phase appears in the form of dispersoids in the Ni matrix.…”

Section: Methodsmentioning

confidence: 99%

“…In the following, the inuence of the initial powder particle size, the time and temperature of sintering and the atmosphere used in powder processing on the microstructure and plastic properties will be illustrated on Ni. One sample was produced from a nanopowder with the average particle size of about 100 nm by hot-isostatic pressing (HIP) [38]. Before HIP, the glass containing the powder was broken in a glove-box and subsequently encap- Finally, in order to study the eect of the initial powder particle size on the microstructure, a fourth sample was consolidated from a Ni powder with the average particle size of 50 nm by SPS under the same conditions as for the previous specimen.…”

Section: Methodsmentioning

confidence: 99%

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Correlation between Processing Conditions, Lattice Defect Structure and Mechanical Performance of Ultrafine-Grained Materials

Gubicza

2015

Acta Phys. Pol. A

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The mechanical performance of ultrane-grained materials is strongly inuenced by the lattice defect structure, i.e. the vacancy concentration, the type, arrangement and density of dislocations, the planar fault probability, as well as the amount and character of grain boundaries. In this paper, the correlation between the processing conditions, the lattice defect structure and the plastic behavior of ultrane-grained materials is overviewed. For the processing route of severe plastic deformation, the inuence of applied strain, hydrostatic pressure, as well as melting point, stacking fault energy and alloying on grain size, dislocation density and strength is studied. For nanopowder sintering techniques, the eect of atmosphere, temperature and time of consolidation on lattice defects and mechanical properties is discussed in detail.

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“…The latter powder had previously been internally characterized in a separate earlier work, including the determination of its chemical composition by inductively coupled plasma spectroscopy [6].…”

Section: Methodsmentioning

confidence: 99%

Microstructure engineering from metallic powder blends for enhanced mechanical properties

Langlois

Fagnon

Dirras

2010

J. Phys.: Conf. Ser.

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Abstract. The present work focuses on the transformation of high-purity Ni powder blends of controlled volume fractions (40 and 60 %) of nanometre-sized (100 nm) and micrometre-sized (544 nm) particles into bulk samples as part of a strategy for producing ultrafine-grained materials usefully exhibiting both strength and ductility. The process involved cold isostatic pressing at 1.5 GPa and sintering. The resulting bulk samples had relative densities near 95 %, were texture-free, and exhibited two different grain size distributions with an average value of 600 ± 30 nm. The mechanical properties were investigated by compression and microhardness tests, both at room temperature, and compared to the behaviour of a sample processed from micrometre-sized powder only. Samples prepared from the blends exhibited high yield stresses of 440 and 550 MPa after compression, and they did sustain work hardening. Tests conducted before and after compression up to 50 % deformation showed the same relative amount of hardness increase around 20 %, which was three times lower than that of the monolithic sample for which a decrease of the average grain size close to 26 % was measured.

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Microstructure and mechanical behavior of ultrafine-grained Ni processed by different powder metallurgy methods

Cited by 36 publications

References 32 publications

Strength and Ductility of Bi‐Modal Cu

Strength and Ductility of Bi‐Modal Cu

Correlation between Processing Conditions, Lattice Defect Structure and Mechanical Performance of Ultrafine-Grained Materials

Microstructure engineering from metallic powder blends for enhanced mechanical properties

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