Spinodal decomposition of austenite in long-term-aged duplex stainless steel

Conference · Wed Feb 01 04:00:00 EST 1989

OSTI ID:6369255

Chung, H M

Spinodal decomposition of austenite phase in the cast duplex stainless steels CF-8 and -8M grades has been observed after long- term thermal aging at 400 and 350/degree/C for 30,000 h (3.4 yr). At 320/degree/C, the reaction was observed only at the limited region near the austenite grain boundaries. Ni segregation and ''worm-holes'' corresponding to the spatial microchemical fluctuations have been confirmed. The decomposition was observed only for heats containing relatively high overall Ni content (9.6--12.0 wt %) but not in low-Ni (8.0--9.4 wt %) heats. In some specimens showing a relatively advanced stage of decomposition, localized regions of austenite with a Vickers hardness of 340--430 were observed. However, the effect of austenite decomposition on the overall material toughness appears secondary for aging up to 3--5 yr in comparison with the effect of the faster spinodal decomposition in ferrite phase. The observation of the thermally driven spinodal decomposition of the austenite phase in cast duplex stainless steels validates the proposition that a miscibility gap occurs in Fe-Ni and ancillary systems. 16 refs., 7 figs., 1 tab.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6369255
• Report Number(s): CONF-890215-5; ON: DE89009827
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
360105* -- Metals & Alloys-- Corrosion & Erosion
AGING
ALLOYS
AUSTENITE
CARBON ADDITIONS
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DECOMPOSITION
GRAIN BOUNDARIES
HARDNESS
HIGH ALLOY STEELS
HIGH TEMPERATURE
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
SEGREGATION
STAINLESS STEELS
STEELS