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.ALUMINUM 2021 is a cryogenic alloy whose ductility and relative notch toughness are not reduced as the tensile strength increases at the low temperatures. It is tough, weldable, and has good corrosion resistance.