Sintering of One-Component Model Systems: Nucleation and Movement of Dislocations in Necks

Friedrich, E.; Schatt, W.

doi:10.1179/pom.1980.23.4.193

Cited by 23 publications

(8 citation statements)

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“…Moreover, it increases reaching a maximum, then decreases. Such a behaviour has been discussed in previous works [10,12,13], on the basis of the self-activating theory of sintering proposed by Friedrich and Schatt [18][19][20]. During isothermal sintering dislocation density first increases due to the organisation of structural defects emitted during the transformation of the interparticle surface in a grain boundary, then decreases due to recrystallization activated by the achievement of a critical dislocation density.…”

Section: Structural Activity In Sintering Of the Green Partmentioning

confidence: 80%

Sintering shrinkage of uniaxial cold compacted iron: influence of the microstructure on the anisothermal and isothermal shrinkage of uniaxial cold-compacted iron

et al. 2018

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The influence of the microstructure of uniaxial cold-compacted green iron on the sintering shrinkage was investigated. Pores in the green parts are very slightly oriented, while the dimension of the interparticle contact areas is anisotropic. A large and anisotropic anisothermal shrinkage in alpha iron was measured, greater than isothermal shrinkage at the 1120°C. The results were interpreted on the basis of the geometrical and of the structural activity, and the effective diffusivity responsible for neck growth was determined.

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Section: Structural Activity In Sintering Of the Green Partmentioning

confidence: 80%

Sintering shrinkage of uniaxial cold compacted iron: influence of the microstructure on the anisothermal and isothermal shrinkage of uniaxial cold-compacted iron

et al. 2018

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“… Equation (8) was used in [7] to predict the isothermal shrinkage of a 6.9 g cm −3 green iron. Owing to the discrepancy between the measured and the theoretical shrinkage, an effective diffusivity D eff was introduced, accounting from the possible difference between bulk diffusivity of commercial iron powder and pure iron (literature data are available only for pure iron) and for the self-activating mechanism occurring during isothermal sintering [11–13].…”

Section: Resultsmentioning

confidence: 99%

A dilatometry study of the influence of green density on anisothermal and isothermal shrinkage of plain iron green parts

Baselli

Molinari

2020

Powder Metallurgy

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The influence of green density between 6.5 and 7.3 g cm −3 on the anisothermal and isothermal shrinkage of atomized plain iron was investigated by dilatometry. The geometrical activity deriving from the extension of the interparticle contact areas and the structural activity provided by the defectiveness of the interparticle contacts promote anisotropic anisothermal shrinkage starting from 500°C up to the bcc to fcc iron transformation. It displays a minimum at 6.9 g cm −3 , resulting from the combined effects of the thermodynamic driving force and of geometrical and structural activity. Anisothermal shrinkage is caused by an anisotropic increase in the internal radius of the neck. Anisotropic isothermal shrinkage is smaller than the anisothermal one and is almost independent on green density. No anisothermal shrinkage was observed on the tapped powder, demonstrating that anisothermal shrinkage in green specimens is due to geometrical and to structural activity introduced by prior cold compaction.

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“…On a microstructural level, changes in the pore structure are observed in green compacts, with elongated pores present mainly perpendicular to the compaction direction as the contact areas between the powder particles become larger [9,10]. The interparticle contact regions also further change through sintering during which a self-activation effect of the material in regions of increased dislocation density can enhance the sintering process [11][12][13]. This structural activity and its role during sintering can, in turn, be further affected by several processing parameters such as compaction pressure and heating rate [12,14].…”

Section: Introductionmentioning

confidence: 99%

Sintering behaviour of compacted water-atomised iron powder: effect of initial state and processing conditions

et al. 2020

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Conventional ferrous powder metallurgy relies on uniaxial die-pressing of powder before sintering. The operation causes particle rearrangement and deformation and the initial state of the compact ultimately determines the sintering behaviour. In this study, sintering was investigated for water-atomised iron powder compacted at three different pressure levels, with and without admixed graphite. Electron back-scatter diffraction of the powder and compacts showed a large increase in low-angle grain boundaries after compaction. The sintering of the compacts was investigated by means of dilatometry in hydrogen. The initial compaction strongly influences sintering shrinkage, particularly in the low-temperature, high-diffusivity ferrite region which can account for up to 80% of the recorded shrinkage. Only a small fraction of the total shrinkage originates from the austenite phase, even at high sintering temperatures. However, the ratio of sintering shrinkage in ferrite and austenite changes with compaction pressure, carbon content and heating rate.

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Sintering of One-Component Model Systems: Nucleation and Movement of Dislocations in Necks

Cited by 23 publications

References 1 publication

Sintering shrinkage of uniaxial cold compacted iron: influence of the microstructure on the anisothermal and isothermal shrinkage of uniaxial cold-compacted iron

Sintering shrinkage of uniaxial cold compacted iron: influence of the microstructure on the anisothermal and isothermal shrinkage of uniaxial cold-compacted iron

A dilatometry study of the influence of green density on anisothermal and isothermal shrinkage of plain iron green parts

Sintering behaviour of compacted water-atomised iron powder: effect of initial state and processing conditions

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