Densification behavior of mechanically milled Cu-8Â at% Cr alloy and its mechanical and electrical properties

Synthesis and consolidation behavior of Cu-8 at% Cr alloy powders made by mechanical alloying with elemental Cu and Cr powders, and subsequently, compressive and electrical properties of the consolidated alloys were studied. Solid solubility of Cr in Cu during milling, and subsequent phase transformations during sintering and heat treatment of sintered components were analyzed using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The milled powders were compacted applying three different pressures (200 MPa, 400 MPa and 600 MPa) and sintered in H2 atmosphere at 900 °C for 30 min and at 1000 °C for 1 h and 2 h. The maximum densification (92.8%) was achieved for the sample compacted at 600 MPa and sintered for 1000 °C for 2 h. Hardness and densification behavior further increased for the compacts sintered at 900 °C for 30 min after rolling and annealing process. TEM investigation of the sintered compacts revealed the bimodal distribution of Cu grains with nano-sized Cr and Cr2O3 precipitation along the grain boundary as well as in grain interior. Pinning of grain boundaries by the precipitates stabilized the fine grain structure in bimodal distribution.