Kuniteru Mihara

Effect of Carbon Addition on Solidification Structure and Strength of Cu–Cr In Situ Composite

A small amount of carbon was doped into a Cu-15 mass%Cr in situ composite to increase the strength of the material. It is found that in the as-cast state Cr dendrites exhibit a needle shape, which can be deformed into fibers much easier than the equiaxial one. A SIMS analysis with the aid of thermodynamic simulation analysis suggests that Cr carbide exists as a nucleation site of Cr dendrites. The composite has a tensile strength of 1200 MPa and an electrical conductivity of 38% IACS in the cold-worked state, and 960 MPa and 73% IACS after optimized aging treatment.

Effect of Alloying Elements on the Mechanical Properties of Cu-15%Cr In Situ Composites

The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr (mass fraction) in-situ composites were systematically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0.15% to 0.2% promotes the precipitation of Cr particles.