AMS 6478 is a specification if Steel AerMet 100, itself a martensitic steel alloy characterized by ultra-high strength. The robust crystalline structure of AMS 6478 brings superior fracture toughness and ductility, excellent fatigue and stress corrosion cracking resistance, and high fatigue strength.
Due to its excellent mechanical properties, AMS 6478 is used in aircraft applications for manufacturing of landing gear, jet engine shafts, structural members, fasteners, driveshafts, and structural tubing. AMS 6478 is offered in the form of bar and forging.
Recommended heat treatment of AMS 6478 is as followed:
Decarburization is done in an inert atmosphere or a vacuum furnace.
Normalizing is done at 1650°F (899°C) for one hour. Then, air-cool the part until it reaches room temperature.
Anneal the piece at 1250°F (677°C) for 16 hours. The annealed hardness achieved here is 40 HRC.
Solution treatment is done at the temperature range of 1625° F (+/-25°F) or 885°C (+/- 14°C) and lasts one hour.
The standard aging treatment for AMS 6478 is at 900°F (+/-10°F) or 482°C (+/-6°C) for five hours and lasts five hours. Never age below temperatures of 875°F (468°C).