High-strength PM aluminium by milling in ammonia gas and sintering

Cintas, J.; Cuevas, F. G.; Montes, J. M.; Herrera, E. J.

doi:10.1016/j.scriptamat.2005.07.019

Cited by 43 publications

(36 citation statements)

References 12 publications

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“…A wide range of PCAs has been used in practice at a level of about 1-5 wt.% of the total powder charge. The used PCA in this work is stearic acid and 3 wt.% of stearic acid has been widely used in previous studies when ball milling of aluminium powders; this is because 3 wt.% is sufficient to not only prevent excessive cold welding of the milled aluminium but also minimise the contamination of the ball-milled powders [16,18]; therefore, the suggested 3 wt.% of stearic acid is employed and 200 g of aluminium powder without stearic acid was milled followed by 200 g of aluminium powder with 3 wt.% stearic acid in this work.…”

Section: Methodsmentioning

confidence: 99%

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Characterisation and milling time optimisation of nanocrystalline aluminium powder for selective laser melting

Han

Setchi

Evans

2016

Int J Adv Manuf Technol

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The aim of this study is to investigate the properties of high-energy ball-milled nanocrystalline aluminium powders and to determine the optimum milling time required to produce an advanced aluminium powder for selective laser melting (SLM). Previous research has indicated that powders suitable for SLM include milled nanocrystalline aluminium powders with an average grain size of 60 nm and good flowability (Carr index less than 15 %). This study employs advanced nanometrology methods and analytical techniques to investigate the powder morphology, phase identification, average grain size and flowability of ball-milled powders. Stearic acid is used to prevent excessive cold welding of the ball-milled powder and to reduce abrasion of the grinding bowl and balls. The results indicate that, whilst the average particle size achieves a steady state after 14 h of milling, the grain size continues to decrease as the milling time progressed (e.g. the transmission electron microscopy measured average grain size is 56 nm after 20 h of milling compared to 75 nm for 14 h of milling). The aluminium powders milled for 16 and 20 h exhibit good flow behaviour, achieving a Carr index of 13.5 and 15.8 %, respectively. This study shows that advanced nanocrystalline aluminium powders suitable for SLM require ball milling for between 16 and 20 h, with 18 h being the optimum milling time.

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Section: Methodsmentioning

confidence: 99%

“…High-strength aluminium has been produced by attrition milling in an ammonia gas atmosphere and powder consolidation by cold pressing and sintering. Indeed, a bulk sample with an average grain size of 200 nm exhibited a high tensile strength of 515 MPa and outstanding high-temperature behaviour [16].…”

Section: Related Workmentioning

confidence: 99%

Characterisation and milling time optimisation of nanocrystalline aluminium powder for selective laser melting

Han

Setchi

Evans

2016

Int J Adv Manuf Technol

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“…In any case, particle size is always lower than 10 μm for a milling time of 3 h or higher, as determined by SEM measurements. In order to study the powders densification during compaction, and to indirectly [10] estimate their hardness, compressibility curves have been determined (Figure 2). Furthermore, for comparison purposes, the compressibility curve of as-received aluminium powder (AR Al) has been included.…”

Section: Milled Powder Characterizationmentioning

confidence: 99%

“…Traditionally, in the powder metallurgy field, aluminium has been reinforced with a variety of directly-added particles [7,8]. However, it was found that the reinforcement of aluminium powder is more effective when second phases are formed through direct reaction, obtaining finely dispersed phases in the matrix [9,10].…”

Section: Introductionmentioning

confidence: 99%

High temperature behavior of nanostructured Al powders obtained by mechanical alloying under NH3 flow

Caballero¹,

Cintas²,

Cuevas³

et al. 2015

AIP Conference Proceedings

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Abstract. Aluminium powder was mechanically alloyed under ammonia gas flow for different times (1-5 h) in order to produce a second-phase reinforcement, mainly by aluminium nitride (AlN). After milling, powders were consolidated by cold uniaxial pressing and vacuum sintering. A small amount of copper powder was added to the Al milled powder to improve its sintering behavior. Hardness and indirect tensile test were carried out at room and high temperature to evaluate the mechanical properties evolution. Results showed an remarkable hardness increase with the second phases content, even at high temperature (up to 229 HB at 400 ºC). However, the high content of second phases of ceramic nature decreases the ductility, resulting in low values of tensile strength (lower than 160 MPa).

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“…The products manufactured by PM techniques exhibits near net shape that requires few or no further machining steps [16][17][18][19]. Moreover, it presents the ability to synthesise products with controlled porosity and microstructure [20].…”

Section: Introductionmentioning

confidence: 99%

Effect of Sintering Time on the Densification, Microstructure, Weight Loss and Tensile Properties of a Powder Metallurgical Fe-Mn-Si Alloy

Hodgson

Cao

2017

Preprint

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This work investigated the isothermal holding time dependence of the densification, microstructure, weight loss and tensile properties of Fe-Mn-Si powder compacts. Elemental Fe, Mn and Si powder mixtures with a nominal composition of Fe-28Mn-3Si (in weight percent) were ball milled for 5h and subsequently pressed under a uniaxial pressure of 400 MPa. The compacted Fe-Mn-Si powder mixtures were sintered at 1200 °C for 0, 1, 2 and 3 h, respectively. In general, the density, weight loss and tensile properties increased with the increase of isothermal holding time. A significant increase in density, weight loss and tensile properties occurred in the compacts being isothermally held for 1 h, as compared to those with no isothermal holding. However, further extension of isothermal holding time (2 and 3h) only played a limited role in promoting the sintered density and tensile properties. The weight loss of the sintered compacts was mainly caused by the sublimation of Mn in Mn depletion region on the surface layer of the sintered Fe-Mn-Si compacts. The length of the Mn depletion region increased with the isothermal holding time. A single α-Fe phase was detected on the surface of all the sintered compacts, and the locations beyond the Mn depletion region were comprised of a dual dominant γ-austenite and minor ε-martensite.

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High-strength PM aluminium by milling in ammonia gas and sintering

Cited by 43 publications

References 12 publications

Characterisation and milling time optimisation of nanocrystalline aluminium powder for selective laser melting

Characterisation and milling time optimisation of nanocrystalline aluminium powder for selective laser melting

High temperature behavior of nanostructured Al powders obtained by mechanical alloying under NH3 flow

Effect of Sintering Time on the Densification, Microstructure, Weight Loss and Tensile Properties of a Powder Metallurgical Fe-Mn-Si Alloy

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