a vacuum circuit breaker comprising an evacuated envelope and a pair of movable conductive rods within the envelope having points of contact equipped with contact members , wherein the conductive rods slide into and out of engaging contact , the improvement comprising at least one of said contacts having circuit making and breaking contact members formed of an alloy consisting essentially of 9 . 4 wt % to 15 wt % al , 4 . 5 wt % to 20 wt % ni , 0 . 1 wt % to 10 wt % of at least one metal selected from the group consisting of bismuth , tellurium , selenium , antimony and magnesium with copper as the balance of the alloy , wherein said alloy contains an α copper phase ) containing nickel and a γ copper phase ) containing nickel substantially dispersed throughout said alloy .