Effect of atmosphere on sintering of Alumix 431D powder

Pieczonka, T.; Kazior, J.; Szewczyk-Nykiel, Aneta; Hebda, Marek; Nykiel, Marek

doi:10.1179/1743290112y.0000000015

Cited by 28 publications

(50 citation statements)

References 22 publications

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“…As was proved experimentally [2,3,20,24,25], the reactions of aluminium with nitrogen producing aluminium nitride AlN are responsible for the effective sintering of this metal. Of course, the reaction may be induced if there is direct contact between the metallic aluminium surface and nitrogen.…”

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

“…It may also be added that, although aluminium has a high affinity for oxygen and is preferentially oxidised over nitriding, the formation of the oxide layer is not only controlled by thermodynamics. As LECO analysis showed [2,3,24,25], significant aluminium nitriding evolved within the internal part of the compact is accompanied by a slight oxidation (Table 3). Both aluminium nitriding and oxidation are highly exothermic reactions.…”

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

“…In the case of high purity aluminium powder, however, the formation of a liquid phase below the melting point of Al requires a nitrogen atmosphere that can exothermally react with aluminium and, in this way, locally heat the material above its melting point. Thermal analysis DTA, TG, DSC and dilatometry experiments performed on aluminium powder in a high purity nitrogen atmosphere [2,3,[20][21][22][23][24][25] indicate both strong exothermic reactions and densification occurring at a high rate, which is specific to liquid phase sintering.…”

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

“…Researchers investigating the sintering mechanisms of aluminium and its alloys tend to agree [2,3,[17][18][19][20][21][22][23][24][25] that successful sintering requires a liquid phase that penetrates the stable, but spalled, aluminium oxide film covering the powder particles. For any aluminium based pre-alloyed powder or elemental powder mixture the appearance of a liquid phase during sintering results from the presence of alloying elements, like Cu, Mg, Zn, Sn, forming low melting point alloys with Al.…”

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

“…1. Detailed DSC curve for isothermal sintering of tap density aluminium powder layer, temperature 620°C, nitrogen 5N [24] Integrating the area below the exothermal peak gives the value of 1473 J/g. Since the specific heat of aluminium is 0.9 J/gK, about 45 J of energy is sufficient to raise the temperature of 1 g Al by 50°C.…”

Section: Dsc Mw/mgmentioning

confidence: 99%

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Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Pieczonka¹

2017

Archives of Metallurgy and Materials

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Aluminium oxide layer on aluminium particles cannot be avoided. However, to make the metal-metal contacts possible, this sintering barrier has to be overcome in some way, necessarily to form sintering necks and their development. It is postulated that the disruption of alumina layer under sintering conditions may originate physically and chemically. Additionally, to sinter successfully non alloyed aluminium powder in nitrogen, the operation of both types mechanism is required. It is to be noted that metallic aluminium surface has to be available to initiate reactions between aluminium and the sintering atmosphere, i.e. mechanical disruption of alumina film precedes the chemical reactions, and only then chemically induced mechanisms may develop. Dilatometry, gravimetric and differential thermal analyses, and microstructure investigations were used to study the sintering response of aluminium at 620°C in nitrogen, which is the only sintering atmosphere producing shrinkage.

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Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

Section: Local Heating Of the Sintered System Resulting In Higher Lomentioning

confidence: 99%

Section: Dsc Mw/mgmentioning

confidence: 99%

See 3 more Smart Citations

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Pieczonka¹

2017

Archives of Metallurgy and Materials

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Application of a device used for observation of controlled thermal processes in a furnace

Hebda

Laska

Szechyńska‐Hebda

2013

J Therm Anal Calorim

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This paper describes an appliance that allows to visually observe phenomena occurring in the studied materials during heating, from room temperature to 600°C. The design criteria and device construction are described in details. The device allows for visual observation of physical phenomena of various material types, e.g., organic matter, polymers, and even observation of sintering mechanisms. Analysis of lubricant evaporation from powder metals (an aluminum alloy) in different atmospheres is shown. The featured device can also be used for interpretation of material defects. This is presented on the example of heating the aluminum alloy in an atmosphere containing oxygen (to simulate a furnace leakage). In addition, the influence of experimental atmosphere on melting and sintering processes is demonstrated. Another application of the presented device can be the visual observation of differences between combustion and pyrolysis processes. Our results show that the presented device is complementary with an advanced thermoanalysis apparatus which, in turn, does not allow visual observation of samples.

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Effect of mechanical alloying and annealing on the sintering behaviour of AstaloyCrL powders with SiC and carbon addition

Hebda

Gądek

Skałoń

et al. 2013

J Therm Anal Calorim

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Alloying is one of the several effective ways of increasing the properties of iron-based PM materials. Modifying the chemical composition of AstaloyCrL powder by silicon addition offers subsequent, effective way of increasing the properties of iron-based PM materials. However, silicon has a high affinity for oxygen, therefore, its implementation is problematic during the sintering process of mixtured powders. In order to overcome this problem and to obtain a homogeneous composition of lowalloy steel with silicon addition, it seems that mechanical alloying (MA) is the most useful process. In order to better understand the sintering behaviour of low-alloy steel modified by silicon, the aim of the present study was to determine the effect of the MA process on AstaloyCrL powder with the addition of silicon in the form of silicon carbide and 0.4/0.6 mass% graphite on the thermal effects during heating measured by differential scanning calorimeter and thermogravimetry techniques. Removal of lubricants during heating of the blended powders as well as exhaust gases from the furnace were monitored by quadruple mass spectrometry. Furthermore, both a light optical microscope and a scanning electron microscope were used for microstructure analysis. Moreover, Thermo-Calc computer software program were used to calculate the enthalpy changes and the volume fraction of phases.

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Effect of atmosphere on sintering of Alumix 431D powder

Cited by 28 publications

References 22 publications

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Application of a device used for observation of controlled thermal processes in a furnace

Effect of mechanical alloying and annealing on the sintering behaviour of AstaloyCrL powders with SiC and carbon addition

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