Liquid phase sintering of aluminium alloys

Schaffer, G. B.; Sercombe, T.B.; Lumley, Roger

doi:10.1016/s0254-0584(00)00424-7

Cited by 176 publications

(130 citation statements)

References 52 publications

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“…Secondphase materials that melt below the sintering temperature are frequently added to powder compacts to accelerate densification (28,29). Owing to their 100% density, our Al-Cu specimens are expected to mimic the late-stage behavior of a liquid-phase sintering system, which is marked by a negligible amount of residual porosity and by coarsening of the solid particles via Ostwald ripening (30,31).…”

Section: Significancementioning

confidence: 99%

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

Dake

Oddershede

Sørensen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Sintering is a key technology for processing ceramic and metallic powders into solid objects of complex geometry, particularly in the burgeoning field of energy storage materials. The modeling of sintering processes, however, has not kept pace with applications. Conventional models, which assume ideal arrangements of constituent powders while ignoring their underlying crystallinity, achieve at best a qualitative description of the rearrangement, densification, and coarsening of powder compacts during thermal processing. Treating a semisolid Al-Cu alloy as a model system for late-stage sintering-during which densification plays a subordinate role to coarsening-we have used 3D X-ray diffraction microscopy to track the changes in sample microstructure induced by annealing. The results establish the occurrence of significant particle rotations, driven in part by the dependence of boundary energy on crystallographic misorientation. Evidently, a comprehensive model for sintering must incorporate crystallographic parameters into the thermodynamic driving forces governing microstructural evolution.3D microstructural evolution | sintering | Ostwald ripening | grain rotation | x-ray imaging W hether we realize it or not, our daily lives are marked by encounters with sintering, ranging from natural rock formations and glaciers to artificial products like the porcelain from which we eat or the amalgam fillings in many teeth. Sintering is an efficient method for combining loose granular precursors into solid objects of predetermined shape at relatively low temperature, circumventing the processing route of melting, casting, and machining. The applications of sintering are widespread. For example, it is the predominant method for producing bulk technical ceramics (1), and, thanks to advances in powder metallurgy, sintering is of growing importance in the fabrication of metals, as well (2). The focus in recent years on nanostructured materials-specifically, on materials for energy storage and conversion-has intensified the scientific investigation and modeling of sintering processes. The latter find application in the production of fuel cells (3) and battery electrodes (4). In other applications, such as catalysis (5), sintering can be highly undesirable, as it reduces the connectivity of pores and the free surface of nanoparticles. In all of these cases, we need a firm understanding of sintering fundamentals to achieve and retain desired materials properties during thermal processing.The reduction in free energy that accompanies the removal of a powder compact's surface area is the driving force behind sintering (2, 6). When two particles come into contact, two free surfaces are replaced by a single solid/solid boundary. If the particles are crystalline, the new interface is a grain boundary, the (excess) energy of which is generally on the order of one-third of that of a (single) free surface of equal area (6); consequently, the sintering process results in a net release of energy. As free surface area decreases, the powder ...

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Section: Significancementioning

confidence: 99%

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

Dake

Oddershede

Sørensen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Previous investigations [12 17] show that sintering contributes to the formation of secondary porosity during transient liquid phase sintering (LPS) the swelling presented seems to be related to the amount of liquid generated (the deeper information about the LPS phenomenon is presented in review [18] and concerning aluminium PM alloys in [19,20]). The mix of primary, secondary and residual porosity is revealed by the mean values of pores size decreasing with increasing pressing pressure.…”

Section: Resultsmentioning

confidence: 99%

The Porosity Evaluation during ECAP in Aluminium PM Alloy

et al. 2012

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The main aim of this paper is to show porosity evolution during application of various processing conditions including pressing, sintering and equal channel angular pressure. An aluminium based powder (Al Mg Si Cu Fe) was used as investigated material. After applying di erent pressing pressures (400 and 600 MPa), specimens were dewaxed in a ventilated furnace at 400 • C for 60 min. Sintering was carried out in a vacuum furnace at 610 • C for 30 min. The specimens were processed by single equal channel angular pressure pass. A signi cant disadvantage of powder metallurgy processing methods is the presence of porosity. Pores act as crack initiators and, due to their presence, the distribution of stress is inhomogeneous across the cross-section and leads to reduction of the e ective load bearing area. The equal channel angular pressure process, causing stress distribution in deformed specimens, made the powder particles to squeeze together to such an extent that the initially interconnected pores transform to small isolated pores. The proposed safety diagram includes the combined e ect of stress and strain behaviour during equal channel angular pressure. The safety line eliminates and quanti es the e ect of large pores as a potential fracture initiation sites with respect to the mechanical viewpoint.

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“…Generally there was no solubility between the liquid and solid, so the densification occurred at the rate associated with sintering the solid skeleton and the liquid is simply a pore filling agent [39,40].The amount of the liquid phase had a significant impact on the sintering trajectory. It seemed that liquid phase infiltrate into space between ceramic agglomerate, the more liquid amount was required to obtain the enhanced sinterability of composite materials [38].…”

Section: Liquid Phases Formationmentioning

confidence: 99%

“…It seemed that liquid phase infiltrate into space between ceramic agglomerate, the more liquid amount was required to obtain the enhanced sinterability of composite materials [38]. Moreover, in Al 2 O 3 particles reinforced Al-MMCs the heat capacity of Al 2 O 3 should be considered fully [40,41]. Because the heat capacity of Al 2 O 3 was relatively large, heat was concentrated on Al matrix around Al 2 O 3 particles in case of composite powder, the fast diffusion of liquid phase would be emerged.…”

Section: Liquid Phases Formationmentioning

confidence: 99%

Advance on Al₂O₃Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs) Manufactured by the Power Metallurgy(PM) Methods- Improved PM Techniques

Zhang

Yue

et al. 2016

MATEC Web Conf.

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Abstract. Aluminum metal matrix composites (Al-MMCs) with Al 2 O 3 particulates as reinforcement fabricated by the power metallurgy (PM) methods have gained much attention due to their unique characteristics of the wide range of Al 2 O 3 particles addition, easy-operating process and effectiveness. The improved PM techniques, such as the high energy ball milling, powder extruder and high pressure torsion were applied to further strengthening the properties or/and diminishing the agglomeration of strength particles. The formation of liquid phase assisted densi¿cation of compacts to promote the sintering of composites. Complex design of Al 2 O 3 particles with other particles was another efficient method to tailor the properties of Al-MMCs.

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Liquid phase sintering of aluminium alloys

Cited by 176 publications

References 52 publications

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

The Porosity Evaluation during ECAP in Aluminium PM Alloy

Advance on Al₂O₃Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs) Manufactured by the Power Metallurgy(PM) Methods- Improved PM Techniques

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Liquid phase sintering of aluminium alloys

Cited by 176 publications

References 52 publications

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

Direct observation of grain rotations during coarsening of a semisolid Al–Cu alloy

The Porosity Evaluation during ECAP in Aluminium PM Alloy

Advance on Al2O3Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs) Manufactured by the Power Metallurgy(PM) Methods- Improved PM Techniques

Contact Info

Product

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Advance on Al₂O₃Particulates Reinforced Aluminum Metal Matrix Composites (Al-MMCs) Manufactured by the Power Metallurgy(PM) Methods- Improved PM Techniques