BRUSH CASTING ALLOYS 165C AND 165CT are beryllium copper alloys of high strength with cobalt as the second alloying element (0.20 to 0.65% Co). Use is in the age-hardened temper. Brush casting alloy 165CT is the fine-grained version. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on casting, heat treating, and machining. Filing Code: Cu-576. Producer or source: Brush Wellman Inc..