Nickel Alloy 400 and Monel 400, also known as UNS N04400, is a ductile nickel-copper-based alloy consisting primarily of two-thirds nickel and one-third copper. Nickel Alloy 400 is known for its resistance to a variety of corrosive conditions, including alkalis (or acids), salt water, hydrofluoric acid, and sulfuric acid. Since Monel 400 or Alloy 400 is a cold worked metal, this alloy has high hardness, stiffness and strength. By cold working ASTM B164 UNS N04400 bar stock, the alloy is subjected to higher levels of mechanical stress, which in turn causes changes in the alloy’s microstructure.