Temperature dependence of strain hardening and plastic instability behaviors in austenitic stainless steels

Journal Article · Mon Aug 02 00:00:00 EDT 2004 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2004.05.003· OSTI ID:20634731

Byun, T S; Hashimoto, N; Farrell, K

The temperature dependencies of true strain-hardening and plastic-instability properties are investigated for austenitic stainless steels; including annealed 304, 316, 316LN, and 20% cold-worked 316LN, at test temperatures from -150 to 450 deg.C. In both annealed and cold-worked conditions, strength decreases with increasing temperature, while ductility peaks below room temperature and is least at about 400 deg.C. At room temperature or below, the strain-hardening behavior exhibits two stages consisting of a rapid decrease for small strains and an increase-decrease cycle before plastic instability occurs. At higher temperatures the strain-hardening rate decreases monotonically with strain. The characteristics of these strain-hardening behaviors are explained by changes in deformation microstructure. Transmission electron microscopy (TEM) of the deformed 316LN steel shows that twins, stacking faults, and/or martensite laths, along with dislocations, are formed at subzero temperatures, and dislocation-dominant microstructures at elevated temperatures. It is also shown that the average strain-hardening rate during necking to failure is almost equal to the true stress at the onset of necking. This stress is called the plastic instability stress (PIS). Cold-worked specimens fail by prompt necking at yield when the yield stress exceeds the PIS of annealed material, indicating that the PIS is independent of prior cold work.

• OSTI ID: 20634731
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 13 Vol. 52; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DEFORMATION
DISLOCATIONS
DUCTILITY
INSTABILITY
MARTENSITE
MICROSTRUCTURE
PLASTICITY
STACKING FAULTS
STAINLESS STEEL-304
STAINLESS STEEL-316
STRAIN HARDENING
STRAINS
STRESSES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY