Low Temperature Mechanical and Physical Properties of Age-Hardened Fe-Ni-Cr-Mn Alloys

Abstract

Age-hardened Fe-Ni-Cr alloys with fully stable austenitic structure (for example A286) have excellent strength, ductility, and toughness at cryogenic temperatures.¹ However, high-Ni austenitic alloys such as these show superparamagnetic or weak ferromagnetic behavior, which is undesirable for superconducting machinery at near-liquid helium temperature.² To overcome this undesirable magnetic property, the authors proposed an age-hardenable Fe-Ni-Cr-(6-12)Mn allo~ as a nonmagnetic and high-strength material for cryogenic use.^3,4 This alloy, whose austenitic matrix was fully stable against α martensitic transformation, showed mechanical properties comparable to that of the aged Fe-Ni-Cr alloys at 4 K. The purpose of the present study was to examine the effects of austenite phase stability on the low temperature mechanical and some physical properties of the aged Fe-Ni-Cr-Mn alloy. Therefore, a series of Fe-(16-21)Ni-16Cr- (0 or 6)Mn alloys were prepared, and tensile tests, Charpy impact tests, magnetic measurements, and dilatometric measurements were carried out.