AMS 5656 is a sub-type specification of 21-6-9, a high-manganese and nitrogen-strengthened stainless steel, available on Tech Steel & Materials as bars and forgings.
The 21-6-9 alloy possesses many favorable properties, including outstanding resistance to oxidation at higher temperatures, exceptional air corrosion resistance, and good resistance to molten lead oxide corrosion.
Moreover, AMS 5656 bars and forgings have high strength and low magnetic permeability in the annealed condition, and excellent impact toughness at cryogenic temperatures, down to -382 °F (-230 °C).
Thanks to its properties, AMS 5656 is widely used in the aerospace industry for the manufacturing of aircraft engine components. Furthermore, the alloys also find use in steam and autoclave parts, and chemical and pollution control equipment.
Bars and forgings from this specification can be machined using traditional methods. However, due to the high work hardening rate of the alloy, higher forces should be applied than on similar stainless steel alloys. AMS 5656 is readily welded using shielded fusion and resistance welding methods, using a filler metal.
AMS 5656 can be hot worked, and cold worked using traditional methods, without any preheating required. Heat treatment in solution is recommended for achieving higher strength of the parts.