Electron microscopy characterization of mechanically alloyed and hot consolidates Cu-Cr3C2 particles

Abstract

Mechanically alloyed copper-ceramic composites have been obtained with the purpose of studying their use as copper-based material for electrical equipment. For high-temperature applications, dispersion-strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivity, mechanical strength retention and microstructural stability. In this work, powder mixtures of pure copper with 2 vol % Cr₃C₂, milled during 4, 6, 10, 12 and 15 h in a high-energy planetary balls mill under argon atmosphere, were consolidated by hot isostatic pressing, applying a pressure of 100 MPa at 1073 K for two hours, to obtain materials with a fine microstructure. The Cu-Cr₃C₂ alloys were studied by scanning electron microscopy (SEM), electron microprobe (EPMA) and transmission electron microscopy (TEM). Mechanical properties and electrical conductivity were also studied. The average tensile strength and electrical conductivity were found to be 500 MPa and 50 % IACS, respectively. The Cr₃C₂ ceramics show good stability during hot consolidation. Contributing to a further strengthening of the alloy during the hot consolidation, uniformly-distributed Fe-carbide particles of nanometric size precipitated in the copper matrix. Fe-Cr oxycarbides formed in the interphase between Cr₃C₂ particles and the copper matrix cause the low ductility of Cu-Cr₃C₂ alloys. Said particles are attributed to impurities/contamination generated from the milling process.