Plastic deformation of nanocrystalline materials

Hahn, Horst; Mondal, Pia; Padmanabhan, K. A.

doi:10.1016/s0965-9773(97)00135-9

Cited by 199 publications

(88 citation statements)

References 5 publications

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“…It is noted that the microhardness of specimens processed by laser beam under water film is considerably harder than that of specimens processed in air and the substrate (760 HV). The hardness of the top layer of the biomimetic units varies from 1083 to 1127 HV and the values for the top layers after laser surface remelting agreed well with Hahn et al [40] findings. It was shown that Fig.…”

Section: Microhardnesssupporting

confidence: 86%

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Zhou

Wang

Guo

et al. 2010

Journal of Alloys and Compounds

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a b s t r a c tCoupling with bionic principles, an attempt to improve the wear resistance of ball bearing steel (GCr15) with biomimetic units on the surface was made using a pulsed Nd: YAG laser. Air and water film was employed as processing medium, respectively. The microstructures of biomimeitc units were examined by scanning electron microscope and X-ray diffraction was used to describe the microstructure and identify the phases as functions of different mediums as well as water film with different thicknesses. The results indicated that the microstructure zones in the biomimetic specimens processed with water film were more refined and had better wear resistance increased by 55.8% in comparison with that processed in air; a significant improvement in microhardness was achieved by laser surface melting. The application of water film provided considerable microstructural changes and much more regular grain shape in biomimetic units, which played a key role in improving the wear resistance of ball bearing steel.

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Section: Microhardnesssupporting

confidence: 86%

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Zhou

Wang

Guo

et al. 2010

Journal of Alloys and Compounds

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“…grain boundary sliding, grain boundary rotation, grain boundary diffusion, triple junction effect, etc. Hahn et al [295,296] have proposed a phenomenological mesoscopic model to explain the inverse H-P relation of nanostructured materials. The inverse H-P effect is considered to be associated with the sliding of grain boundaries.…”

Section: Mechanical Behaviormentioning

confidence: 99%

Nanocrystalline materials and coatings

Tjong

Chen

2004

Materials Science and Engineering: R: Reports

837

345

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In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of $0.1 to 0.3 mm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value ($10-20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process. #

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“…Hahn and co-workers 79,80 suggest that the reverse HallPetch effect is caused by deformation in the grain boundaries. If a grain boundary slides, stress concentrations build up where the grain boundary ends, limiting further sliding.…”

Section: B Reverse Hall-petch Effectmentioning

confidence: 99%

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

et al. 1999

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Nanocrystalline metals, i.e., metals in which the grain size is in the nanometer range, have a range of technologically interesting properties including increased hardness and yield strength. We present atomic-scale simulations of the plastic behavior of nanocrystalline copper. The simulations show that the main deformation mode is sliding in the grain boundaries through a large number of uncorrelated events, where a few atoms ͑or a few tens of atoms͒ slide with respect to each other. Little dislocation activity is seen in the grain interiors. The localization of the deformation to the grain boundaries leads to a hardening as the grain size is increased ͑reverse Hall-Petch effect͒, implying a maximum in hardness for a grain size above the ones studied here. We investigate the effects of varying temperature, strain rate, and porosity, and discuss the relation to recent experiments. At increasing temperatures the material becomes softer in both the plastic and elastic regime. Porosity in the samples result in a softening of the material; this may be a significant effect in many experiments. ͓S0163-1829͑99͒05941-X͔

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Plastic deformation of nanocrystalline materials

Cited by 199 publications

References 5 publications

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Influence of processing medium on frictional wear properties of ball bearing steel prepared by laser surface melting coupled with bionic principles

Nanocrystalline materials and coatings

Atomic-scale simulations of the mechanical deformation of nanocrystalline metals

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