Papers by Keyword: Sintered Properties

Abstract: Cu powder extrusion developed in this work is aimed to be a pilot processing technique to plausibly replace conventional metal extrusion, which is higher in energy consumption and hence causes negative environment impact. In this study, both spherical- and irregular-shape Cu powders were used. 5 different binder formulae comprising low density polyethylene (LDPE); paraffin wax; and stearic acid of 25:70:5, 30:65:5, 35:60:5, 40:55:5 and 45:50:5 by weight were studied. Wettability between the binders and Cu powder of all formulae observed by naked eye appeared to be satisfactory. The binders were then mixed with 60% by volume of Cu powder. Rheological properties, observed using a capillary rheometer with 2 mm diameter orifice at 95°C, determined that the last 2 formulae gave sufficient green strength in the extrudate. However, only the latter binder formula gave extrudate with smooth surface. Downward extrusion with 45 cm distance from the die gave straight extrudates and no any distortion or warpage was found. Solvent debinding conditions using hexane at 40, 50 and 60°C were studied. The debinding at 50°C was the most effective in dissolving the binder and ensured that the Cu powder remained intact. The 15 cm-long Cu extrudates were sintered in H2 atmosphere at 1030°C for different times. Density and tensile strength of the sintered extrudates were determined.

Abstract: Sintered Fe-5 wt. % carbide (SiC or TiC) composites have been prepared via a powder metallurgy (P/M) route. Two carbide particle sizes, < 20 µm and 20-32 µm, were mixed with Fe powder. The powder mixtures were compacted and sintered at 3 different temperatures, 1100, 1150 and 1200 °C. Microstructures of sintered Fe-5 wt. % SiC composites showed evidence of SiC decomposition. The decomposed Si and C atoms diffused into Fe particles resulting in formation of solid solution of Si and C in Fe during sintering. During cooling, the solid solution of C in Fe decomposed to pearlite structure (ferrite and cementite (Fe3C) lamellar structure). Microstructures of sintered Fe-5 wt. % TiC composites showed no evidence of TiC decomposition at the investigated sintering temperatures. Because of the reaction between SiC and Fe, tensile strength and hardness of the sintered Fe-SiC composites were higher than those of the sintered Fe. Experimental results showed that strength and hardness of the sintered Fe-SiC composites increased with increasing sintering temperature and with decreasing SiC particle size. In contrast, mechanical properties of the sintered Fe-TiC composites were inferior to those of the sintered Fe. The reason of poor mechanical properties may be attributed to poor bonding between Fe and TiC particles.