Microstructure and tensile behavior of nitrogen-alloyed, dual-phase stainless steels

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Metallurgical Transactions, A

DOI:https://doi.org/10.1007/BF02651934· OSTI ID:282234

Berns, H ^[1]; Kleff, J ^[2]; Krauss, G ^[3]; Foley, R P ^[4]

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1. Ruhr Univ. Bochum (Germany). Lehrstuhl Werkstofftechnik
2. ZF Friedrichshafen AG (Germany)
3. Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgical and Materials Engineering
4. Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Metallurgical and Materials Engineering

Two alloys of high-nitrogen stainless steel have been heat treated to produce dual-phase microstructures. The first alloy, N10CrNiMo17 1, a Ni-containing stainless steel, was processed conventionally. The second alloy, N20CrMo17, a Ni-free stainless steel, was processed to obtain a higher nitrogen content by pressurized electroslag remelting. The martensite in N10CrNiMo17 1 was homogeneously distributed in the ferrite and obtained a near-constant volume fraction as a function of intercritical annealing temperature. Microprobe analysis and microhardness measurements of the martensite constituent suggested that up to 0.4 pct N was dissolved in the austenite before quenching. Austenite formation, martensite transformation, undissolved nitrides, and retained austenite were evaluated by transmission electron microscopy (TEM). The Ni-containing alloy exhibited classic dual-phase tensile behavior in that continuous yielding was observed together with good combinations of ultimate tensile strength and total elongation. The martensite constituent in alloy N20CrMo17 was concentrated within bands. Comparison of tensile properties of the two alloys at similar volume fractions and hardness levels of martensite and ferrite showed that the microstructure containing banded martensite had inferior combinations of strength and ductility. The degradation of tensile ductility was accompanied by a fracture mode transition from microvoid coalescence to transgranular cleavage. The deformation and fracture behavior of both alloys were related to the microstructure.

• Sponsoring Organization: USDOE
• OSTI ID: 282234
• Journal Information: Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 7 Vol. 27; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AUSTENITE
CHROMIUM-MOLYBDENUM STEELS
CHROMIUM-NICKEL-MOLYBDENUM STEELS
DUCTILITY
ELECTRON MICROPROBE ANALYSIS
ELONGATION
FERRITE
FRACTURE PROPERTIES
HEAT TREATMENTS
MARTENSITE
METALLURGICAL EFFECTS
MICROHARDNESS
MICROSTRUCTURE
NITROGEN
TENSILE PROPERTIES
TRANSMISSION ELECTRON MICROSCOPY
ULTIMATE STRENGTH