201. LOW TEMPERATURE PROPERTIES OF HIGH-MANGANESE-MOLYBDENUM AUSTENITIC IRON ALLOYS
- Author
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K. Nagai, K. Ishikawa, Toshio Ogata, and K. Hiraga
- Subjects
Austenite ,Toughness ,Materials science ,Metallurgy ,Alloy ,Charpy impact test ,chemistry.chemical_element ,engineering.material ,Stress (mechanics) ,chemistry ,Molybdenum ,Phase (matter) ,engineering ,Austenitic stainless steel - Abstract
Austenitic stainless steels are prominent materials for cryogenic service in superconducting technology applications. The materials should be nonmagnetic at lower temperatures and/or under stress. Transformation from the f.c.c. austenitic phase to the b.c.c. phase brings about ferromagnetic elements, which are dangerously distorted in the strong magnetic field. High-manfanese stable austenitic iron alloys were developed for this purpose.1 Their toughness and phase stability at lower temperatures are excellent enough to satisfy the requirement. However, since they contain lower lower carbon, compounds of which reduce the low-temperature toughness, the strength (0.2% strain proof stress) is suppressed to the lower level. The improvement in the strength is required for the scale-up of structure and the reduction of liquid helium consumption. Generally, the increase in strength inevitably brings about a decrease in toughness.2 The desirable strengthening methods should be selected from those that do not reduce the toughness much at lower temperatures. Molybdenum is one of the most effective elements in strengthening austenitic iron alloy through solidsolution strengthening.