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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2008

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Mechanical and physical properties of sintered aluminum powders

Findik F., Gökçe A.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 30, nr 2

157-164

Purpose: The purpose of the work is to compare the physical and mechanical properties for argon atomized Al-1wt-%Mg powders with and without lubricant 1wt% Acrawac. Pure nitrogen sintering was performed and the effect of sintering atmosphere for the mixed Al-1%Mg powder compacts was investigated. Design/methodology/approach: One weight percent Acrawax was premixed with the powder as a lubricant for the first group samples. However, no wax was used for the second group specimens. As a sintering aid, 1wt% Mg was added for both group materials. Compaction of the specimens was performed using a hand operated Carver hydraulic press and a floating rectangular die. First group specimens were pressed to green densities of 91.5 and 92.5% using pressures of 435 and 490 MPa, respectively. In the second group (no wax) samples, 93% green density was obtained using the similar compaction pressures. Sintering and delubrication occurred in a horizontal tube furnace with a high purity nitrogen atmosphere. The nitrogen flow rate was : 1.5 l min⁻¹. The heating rate from the dewaxing to sintering temperature was 10°C min⁻¹. While the sintering temperature kept at 640°C, sintering time varied between at 2 h and 6 h. Three point bending samples were examined using Instron machine using 25.4 span between the lower supports and 2 mm/min strain rate. Findings: Green and theoretical density increased with the increment of compaction pressure. Although Acrawax lubricant provides a reasonable green density, it had a deleterios effect on sintered density mainly owing to its wide burn off range and hence incomplete removal during sintering leaving some black residue. Research limitations/implications: Residual macro- and microporosity was present in all sintered samples under every sintering condition. Medium sized pores and small interconnected micro-pores at grain boundaries were visible when lubricant was added which reduced the sintered densities due to a wide burn off range leaving residual porosity. Originality/value: Mechanical and physical properties of sintered aluminum powders were evaluated.