Influence of post-anneal cooling treatments on suppression of cryogenic intergranular fracture in experimental Ni-free high-Mn austenitic steels
The influence of thermal history on the grain boundary chemistries and cryogenic mechanical properties of two high-Mn austenitic steels are examined. While high-Mn alloys with excellent toughness at 4K have been developed, the Ni-free high-Mn alloys are susceptible to cryogenic intergranular embrittlement. Both the source of this embrittlement and the conditions necessary for its control have remained poorly understood. In quaternary Fe-30Mn-5Cr-0.16N and Fe-30Mn-5Cr-0.22N alloys the cryogenic toughness is strongly dependent on cooling rate. The 77K Charpy impact toughness of Fe-30Mn-5Cr-0.16N increases with decreasing cooling rate from 41 J after a brine-quench to 183 J after air-cooling. The influence of post-quench isothermal tempering treatments between 723 and 1023K on the impact toughness is also measured. The grain boundary chemistries of brine-quenched and air-cooled samples were examined by Auger electron spectroscopy. No grain boundary segregation of Mn is observed but both N and slight Cr enrichments are present. While no segregation of common embrittling species occurs, boron segregates to the grain boundaries during slow-cooling. 13 refs., 2 figs., 6 tabs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5802576
- Report Number(s):
- LBL-23853; CONF-8706125-21; ON: DE88002766
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ANNEALING
AUGER ELECTRON SPECTROSCOPY
AUSTENITIC STEELS
BORON ADDITIONS
BORON ALLOYS
CARBON ADDITIONS
CHARPY TEST
CHEMICAL COMPOSITION
COOLING
CRYOGENICS
CRYSTAL STRUCTURE
DESTRUCTIVE TESTING
ELECTRON SPECTROSCOPY
EMBRITTLEMENT
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HEAT TREATMENTS
IMPACT TESTS
IRON ADDITIONS
IRON ALLOYS
IRON BASE ALLOYS
LOW TEMPERATURE
MANGANESE ALLOYS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
MICROSTRUCTURE
NITROGEN ADDITIONS
OXYGEN ADDITIONS
PHOSPHORUS ADDITIONS
SEGREGATION
SILICON ADDITIONS
SILICON ALLOYS
SPECTROSCOPY
STEELS
TEMPERATURE EFFECTS
TENSILE PROPERTIES
TESTING
VERY HIGH TEMPERATURE
YIELD STRENGTH