DISPERSION STRENGTHENING OF COPPER-ALLOYS

Copper alloys with high electrical and thermal conductivities in combi nation with high strength at elevated temperature have been developed by including very fine thermodynamically stable TiC dispersoids into a Cu or an age-hardenable CuTi4 matrix. TIC dispersion strengthened cop per alloys were prepared by mechanical alloying in a planetary ball mi ll using a blend of atomized prealloyed CuTi(X) powder and graphite po wder. The mechanism of the formation of TiC dispersoids during milling and heating at various temperatures was investigated using X-ray diff raction and by TEM investigations. The processing technique was found to result in TiC dispersoids of different sizes (diameter 10 to 50 nm) preferentially localized on the grain boundaries. The matrix of the a lloys is microcrystalline (grain size 100 to 500 nm). The observed cre ep behaviour of the alloys is described in dependence on size and volu me fraction of the dispersoids and the composition of the matrix. It i s demonstrated that these alloys - despite their microcrystalline micr ostructure - show a high creep strength, provided numerous small dispe rsoids are located on the grain boundaries, thus effectively preventin g grain boundary sliding.