View Sample Alloy Digest Data Sheet (PDF)Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.BRUSH CASTING ALLOY 21C is a Beryllium copper alloy of high strength with cobalt as the second alloying element. Use is in age-hardened temper.