Austenite decomposition during continuous cooling of an HSLA-80 plate steel

Journal Article · Sat Jun 01 00:00:00 EDT 1996 · Metallurgical Transactions, A

OSTI ID:264075

Thomspon, S W; Colvin, D J; Krauss, G ^[1]

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1. Colorado School of Mines, Golden, CO (United States)

Decomposition of fine-grained austenite (10-{micro}m grain size) during continuous cooling of an HSLA-80 plate steel (containing 0.05C, 0.50Mn, 1.12Cu, 0.88Ni, 0.71Cr, and 0.20Mo) was evaluated by dilatometric measurements, light microscopy, scanning electron microscopy, transmission electron microscopy, and microhardness testing. Between 750 C and 600 C, austenite transforms primarily to polygonal ferrite over a wide range of cooling rates, and Widmanstaetten ferrite sideplates frequently evolve from these crystals. Carbon-enriched islands of austenite transform to a complex mixture of granular ferrite, acicular ferrite, and martensite (all with some degree of retained austenite) at cooling rates greater than approximately 5 C/s. Granular and acicular ferrite form at temperatures slightly below those at which polygonal and Widmanstaetten ferrite form. At cooling rates less than approximately 5 C/s, regions of carbon-enriched austenite transform to a complex mixture of upper bainite, lower bainite, and martensite (plus retained austenite) at temperatures which are over 100 C lower than those at which polygonal and Widmanstaetten ferrite form. Interphase precipitates of copper form only in association with polygonal and Widmanstaetten ferrite. Kinetic and microstructural differences between Widmanstaetten ferrite, acicular ferrite, and bainite (both upper and lower) suggest different origins and/or mechanisms of formation for these morphologically similar austenite transformation products.

• OSTI ID: 264075
• Report Number(s): CONF-941016-; ISSN 0360-2133; TRN: IM9633%%9
• Journal Information: Metallurgical Transactions, A, Vol. 27, Issue 6; Conference: Materials week `94, Rosemont, IL (United States), 3-7 Oct 1994; Other Information: PBD: Jun 1996
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
IRON BASE ALLOYS
PHASE TRANSFORMATIONS
COPPER ALLOYS
MANGANESE ADDITIONS
NICKEL ADDITIONS
CHROMIUM ADDITIONS
MOLYBDENUM ADDITIONS
DILATOMETRY
OPTICAL MICROSCOPY
SCANNING ELECTRON MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
MICROHARDNESS
WIDMANSTAETTEN STRUCTURE
FERRITE
MARTENSITE
TEMPERATURE DEPENDENCE
BAINITE
KINETICS
MICROSTRUCTURE
GRAIN SIZE