Stereological characterization of the interaction between interfaces and its application to the sintering process

Aigeltinger, E. H.; Exner, Hans Eckart

doi:10.1007/bf02661751

Cited by 43 publications

(26 citation statements)

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“…Density, surface area, and grain size are useful sintering metrics, since there is a natural trajectory evident over a range of materials, particle sizes, and processing techniques. [4][5][6][7][8] Crystalline materials first give up surface area to form grain boundaries at the interparticle bonds. Late in sintering, grain growth removes grain boundary area as densification continues.…”

Section: Introductionmentioning

confidence: 99%

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Sintering Trajectories: Description on How Density, Surface Area, and Grain Size Change

German

2016

JOM

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Sintering is a mainstay production step in forming metal, ceramic, polymer, and composite components from particles. Since the 1940s, the sintering process is treated using a matrix of mathematical relationships that include at least seven atomic transport mechanisms, several options on powder characteristics, and three pore-grain morphology options. The interplay of these relationships is handled by numerical solutions to predict property development. An alternative approach is to track the sintering trajectory using relatively simple relationships based on bulk measures. Energy minimization dictates that initial stage sintering acts to reduce surface area. In late stage sintering, the energy minimization turns to grain boundary area reduction via grain growth. Accordingly, relationships result between density, surface area, and grain size, which largely ignore mechanistic details. These relationships are applicable to a wide variety of materials and consolidation conditions, including hot pressing, and spark sintering.

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Section: Introductionmentioning

confidence: 99%

“…4,5,9,15,[18][19][20][21][22] Figure 2 illustrates such behavior using data for urania (UO 2 ) sintering at 1500°C for up to 2000 min. 19 The specific surface area is given relative to the starting surface area versus fractional density with a straight line fit to the data.…”

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confidence: 99%

Sintering Trajectories: Description on How Density, Surface Area, and Grain Size Change

German

2016

JOM

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“…As expected, the values decrease gradually as the solid volume fraction increases. Linear decreases in S v sv with increasing solid volume fraction have been commonly observed in the sintering of powder metals 21,22 and ceramics. 20,23,24 Inspection of Eq.…”

Section: Resultsmentioning

confidence: 97%

The effect of coarse particles on the microstructural evolution of porous alumina sintered at 1375 °C

Schmidt

Nettleship

2004

Journal of the European Ceramic Society

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“…For comparison, the R values of the carbonyl iron compacts heated at 10°C/min and 1200°C/min to 1200°C and then sintered for 60 minutes are 1.95 and 1.81, respectively, in agreement with those reported for tungsten and copper in previous studies. [25,26] However, when compacts are heated at 10°C/min and 1200°C/min to 950°C and then held at that temperature for 5 minutes, the R values are only 1.51 and 1.59, respectively. These low values suggest that the grain boundary distributions in these compacts are close to the case with random intersections and no pinning effect due to the high porosity and fine grain size in the early stage of sintering.…”

Section: Discussionmentioning

confidence: 98%

“…Because such interaction may provide some insight into the effect of rapid heating, a quantitative metallography study was carried out. This method was postulated by Aigeltinger and Exner and was later modified by Patterson et al [25,26] By comparing the measured length of intersection between the grain boundary and the pore surface per unit volume, L M V ; and the calculated length expected for random intersections of the two surfaces per unit volume, L C V ; the ratio R of L M V to L C V gives the degree of excess pore-grain boundary contact and can be given by…”

Section: Discussionmentioning

confidence: 99%

Enhanced Densification of Carbonyl Iron Powder Compacts by the Retardation of Exaggerated Grain Growth through the Use of High Heating Rates

Hwang

Shu

et al. 2009

Metall Mater Trans A

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An investigation of the effect of heating rates on the densification behavior of carbonyl iron powder compacts, particularly on the exaggerated grain growth during the a-c phase transformation, was carried out in this study. Compacts heated at 1200°C/min and then sintered for 90 minutes at 1200°C attained 7.14 g/cm 3 , while those heated at 10°C/min reached only 6.61 g/cm 3 . Dilatometer curves using heating rates of 2°C/min, 5°C/min, 10°C/min, 30°C/min, and 90°C/min demonstrate that 90°C/min yields the highest sintered density. The microstructure analysis shows that high heating rates inhibit exaggerated grain growth during the phase transformation by keeping the interparticle neck size small and pinning the grain boundaries. This explanation is supported by the calculation that shows that the energy barrier preventing the grain boundary from breaking away from the neck is reduced hyperbolically as the neck size and the amount of shrinkage increase. The high heating rate, however, shows little beneficial effect for materials that have no allotropic phase transformation or have less drastic grain growth during heating, such as nickel and copper. Thus, bypassing the low temperatures to suppress the surface diffusion mechanism, which does not contribute to densification, is ruled out as the main reason for the enhanced densification of carbonyl iron powders.

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Stereological characterization of the interaction between interfaces and its application to the sintering process

Cited by 43 publications

References 1 publication

Sintering Trajectories: Description on How Density, Surface Area, and Grain Size Change

Sintering Trajectories: Description on How Density, Surface Area, and Grain Size Change

The effect of coarse particles on the microstructural evolution of porous alumina sintered at 1375 °C

Enhanced Densification of Carbonyl Iron Powder Compacts by the Retardation of Exaggerated Grain Growth through the Use of High Heating Rates

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