EFFECT OF HEAT-TREATMENT ON MECHANICAL AND ELECTRICAL-PROPERTIES OF COMPOCAST DISPERSION-STRENGTHENED COPPERS

An investigation was made on the microstructures and electrical and mechanical properties of dispersion-strengthened (DS) coppers compocast at 25 rev/s with the addition of fine ceramic particles of VB, TaB2, WC, TaC, SIC, TiN, Al2O3, and ZrO2. Homogeneous distribution of all the particles except Al2O3 and ZrO2 was observed in the compocast DS coppers. In the compocast boride particles-dispersed coppers, with the increased addition of 1 to 5 mass%TaB2, the electrical conductivity decreased from 101 to 94.2%IACS; the hardness increased from Hv64.9 to Hv73.9; the ultimate tensile strength increased from 137 MPa to 229 MPa; the elongation value decreased from 47.1% to 33.0%; and the reduction of area decreased from 70.5% to 31.4%. The compocast 10 mass%WC-dispersed coppers were thermomechanically treated by hot extrusion, cold drawing and annealing. The hardness of the hot-extruded and cold-drawn DS coppers increased up to Hv138, which was nearly twice the value of Hv79.6 of the as-compocast DS coppers. The hardness of the hot-extruded, cold-drawn and annealed DS coppers decreased gradually with increasing annealing temperature except when a fluctuation existed. In the 1 mass%WC-dispersed coppers compocast with addition of alloying elements of 1 to 2 mass%Al, Ni and Fe, the electrical conductivity decreased exponentially with the increase in atomic percent of the alloying elements.