The paper presents studies about reducing the sintering temperature of PM High-Speed
Steel obtained by water atomization. The powder was characterized to proceed with compaction and
sintering at different temperatures between 1140-1220°C in different atmospheres: nitrogen (N2),
nitrogen-hydrogen-methane (N2/H2/CH4) and vacuum. It is described the experiment in able to
increase hardness by a quenching and tempering heat treatment that was carried out on sintered
samples at 1140°C in vacuum atmosphere at 1200°C in N2/H2/CH4.
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/cm 3 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.
In this paper, a method of fabricating metallic analogues of biological materials is presented.In particular, the structure of pre-pressed oilseed used for physical modeling of supercritical CO 2 extraction of desired substances is replicated in a material commonly used for manipulation of foods, i.e. food grade stainless steel (AISI 316L).Powder metallurgy approach is employed through sintering the steel powder with SiO 2 spacer and further leaching the porogen. The resulting metal framework has interconnected porosity and low apparent density (about 1.91 g/cm 3 ). The prospect of tuning the balance between porosity and interconnectivity of pores is of special concern to allow mimicking the structure of natural materials intended for supercritical CO 2 extraction. With this motivation, the effects of initial silica content (between 20 to 60 vol.%) and silica particle size (small: 0.5-10 µm, medium: 110 µm, and large: 170-630 µm) on the structural and mechanical properties of the porous material are studied. It is found that increasing porosity correlates with decreasing compressive strength, whereas the plateau region of the stress-strain relationship in compression is of lower slope and spans over larger strain. Yield strength ranges from 4.2 MPa to 220 MPa, which is sufficient for sustaining the conditions of supercritical extraction.
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