Effects of thermomechanical processing on strength and toughness of Fe - 12Ni reactive metal alloys at 77 K

Abstract

Thermomechanical processing (TMP) was evaluated as a method of strengthening normally tough iron-12 nickel-reactive metal alloys at cryogenic temperatures. Five iron-12 nickel alloys with reactive metal additions of aluminium, niobium, titanium, vanadium, and aluminium plus niobium were investigated. The primary evaluation was based on the yield strength and fracture toughness at 77 K. At 77 K, a yield strength of 1.3 GPa (187 ksi) with a corresponding K Icd toughness of 243 MPa m 1 2 (221 ksi in 1 2 ) was achieved with an iron-12 nickel-0.5 aluminium alloy which had undergone a 300 K rolling followed by annealing at 800 to 900 K. This represents the highest combination of cryogenic strength and toughness observed in iron-nickel alloys.