Microstructure and Mechanical Properties of PM Cu Composite Dispersed with Carbon Nanotube

Abstract

Microstructural and mechanical properties of powder metallurgy (PM) copper (Cu) composites dispersed with carbon nanotube (CNTs) were investigated in detail. A pure copper powder was coated with un-bundled CNTs by using the zwitterionic surfactant solution containing CNTs. The powder rolling process was applied to increase the powder surface area to be coated with CNTs. The total rolling reduction of Cu-CNT composite powder by 5 times rolling was about 75%. With increasing the rolling number, the content of CNTs coated on the Cu powder surface increased because of the increment of the flat surface area of flaky Cu rolled powder. As a result, the CNT content was 0.67 mass% after 5 times powder rolling. It was about twice as that of as-coated Cu-CNT composite powder without rolling process. The grain size of PM extruded Cu-CNT composite powder material was about 1/5 of that of the extruded monolithic Cu material without CNT. Yield stress of the extruded material of CuCNT composite via the rolling processing was 192 MPa, and about twice compared to the extruded monolithic Cu material (88 MPa). CNTs distributed at primary particle boundaries were effective to prevent the grain coarsening by their pinning effects, and this grain refinement was a main strengthening factor of the Cu-CNT composite material via rolling process.