Production Process and Properties of a Highly Porous Al Alloy Made Using NaCl Droplets as a Space Holder

doi:10.1007/s40195-015-0291-z

Abstract

Abstract:

Porous Al structures have been made using a porogen leaching method but with additional novel steps. In this way, Al-0.25Cu-0.6Si-1.0Mg alloys with interconnected, open cells have been made, with high levels of porosity (up to 89%). The use of 4 to 5 mm diameter sodium chloride droplets combined with interspersion of the metal powder and droplets in the die and dissolution of the salt before sintering was found to enable easier interspersion of the two components, resulting in good connectivity of the beads via the formation of “windows” between the pores, and rapid elimination of salt from the structure. Porous Al with densities in the range of 0.28-0.86 g/cm³ exhibited compressive yield strengths in the range of 0.14 to 7.5 MPa, with no difference being observed between the samples made by this route and by more conventional dissolution of the salt after sintering. These novel steps widen the possibility for porous metal manufacture to other materials, not limited by the need to have a sintering temperature below that for the melting point of salt.

Key words: Aluminium alloy, Sodium chloride, Porous metal

Manuela Covaciu, Andrew Richard Kennedy. Production Process and Properties of a Highly Porous Al Alloy Made Using NaCl Droplets as a Space Holder[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(8): 1034-1040.

Figures/Tables 8

Fig. 1 Micrographs of the materials used in the study: a Al-0.25%Cu-0.6%Si-1.0%Mg alloy components; b 53-250-μm blocky NaCl powder and 4- to 5-mm droplets at different magnifications

Fig. 2 Schematic representation of NaCl processing into droplets

Fig. 3 SEM micrographs of NaCl powder processed into 4- to 5-mm droplets: a surfaces of the NaCl droplets after processing with water; b, c droplets sintered at 755 °C for 1 h

Fig. 4 Green compact characteristics for 72.46 wt% NaCl compacted at 250 MPa: a SEM micrographs of the NaCl alloy composite; b the Al-0.25Cu-0.6Si-1.00Mg alloy matrix (CSD process); c green compact after dissolution (CDS process)

Fig. 5 Optical microscope micrographs of green compacts (CSD process) showing cell wall size structures for 72.46 wt% NaCl compacted at 250 MPa

Fig. 6 Porous structure densities obtained by CSD and CDS processes

Fig. 7 Macro- and microstructures of porous aluminium alloy obtained by CDS process made with 69.44 wt% NaCl at different compaction pressures: a µCT images for macrostructure; b SEM images showing details of the macrostructure

Fig. 8 Mechanical property data: a stress-strain curves for CDS process; b log-log graph of compressive yield stress (σ y) and density (ρ)

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