Fracture Toughness of Fe-13%Ni-3%Mo-0.2%Ti Alloy at Cryogenic Temperature

Abstract

Fracture tests at cryogenic temperature were carried out on Fe-13%Ni-3%Mo-0.2%Ti alloy for cryogenic service. The results showed that this alloy did not yield cleavage fracture even at 4 K. The temperature dependence of the fracture toughness was smaller than those of the yield and the tensile stress. The clear transition temperature was not observed down to 4 K. The ductile-brittle transition temperature decreased with Ni concentration in B.C.C. iron (α-iron) alloy and was extrapolated to 0 K at about 13% of Ni. This estimated value agreed with the results obtained by Charpy impact test.
The structural materials for cryogenic use should possess high strength and toughness for salty at lower temperature. The yield stress (proof stress) and the fracture toughness of this alloy were 750 MPa at 300K and 90 MPa√m at 4 K, respectively. The good balance between them was satisfied in this alloy.