Mechanical Properties of Microporous Copper Powder Compacts Produced by Oxide Reduction

Abstract

Powder metallurgy (PM) processes for porous copper and alloys have seen some commercial successes, but PM methods have the disadvantage of relatively low porosity or strength that is compromised by stress-concentrating interparticle bonds. To increase porosity without compromising scalability, a Cu-CuO metal matrix composite powder was utilized to produce additional microscale porosity within the particles by oxide reduction. These Cu-CuO powders were pressed at 1, 2, or 3 GPa, and made porous at 600, 800, or 1000 °C to investigate the effects of pressing and sintering parameters on the overall strength and density. It was found that the formation of porosity is weakly dependent on compaction pressure (maximum 6% difference from 1 GPa to 3 GPa), while the final porosity varied by ~16% overall (~40% for 1 GPa and 600 °C to 24% for 3 GPa and 1000 °C). The strength of the porous Cu was highest after being reduced at 600 °C but also exhibited some flaking at the edges at high strain. The 1 GPa, 600 °C samples have a higher specific strength than wrought Cu annealed at the same temperature, as was demonstrated under uniaxial quasi-static compression as well as split Hopkinson pressure bar impact.

Keywords

• solid-state foaming
• porous metals
• compression testing
• additive expansion by reducing oxides
• copper
• copper oxide