| Cu-Cr alloys have been used as precipitation hardened alloys, due to low solubility of Cr in Cu. The strength of copper alloys is known to decrease as precipitates and grain size get coarser as service temperature is increased. Meanwhile, using MA process, higher strengths could be obtained through uniform distribution of fine Cr-particles. In this study, Cu-Cr powder mixtures were mechanically alloyed in order to develop high strength Cu alloys. The properties of extruded bars were investigated using various analytical techniques. The ratio of pre-alloyed powders to steel balls was 1 : 20 and the mechanical alloying was performed for 10hours in Ar atmosphere. TEM observations showed that the Cr-particles were distributed in Cu-matrix, and grain size of the extruded bars was about 100㎚. The tensile strength of extruded bars was found to increase with the volume fraction of Cr and its maximum value was 500㎫ in Cu-4vol%Cr-alloy. The tensile strength was slightly decreased after annealing at 800℃ far 1hours, but greatly decreased after annealing at 900℃ for 1hour. As the result of this study, the strength of Cu-Cr alloys was dependent on the volume fraction of Cr and grain size. |
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