A Stacking Fault Energy Perspective into the Uniaxial Tensile Deformation Behavior and Microstructure of a Cr-Mn Austenitic Steel

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2014-04, Vol.45 (4), p.1937-1952
• Main Authors: Barman, H., Hamada, A. S., Sahu, T., Mahato, B., Talonen, J., Shee, S. K., Sahu, P., Porter, D. A., Karjalainen, L. P.
• Format: Article
• Language: English
• Subjects: Applied sciences; Austenitic stainless steel; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium; Deformation; Density; Dislocations; Exact sciences and technology; Materials Science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metallic Materials; Metallurgy; Metals. Metallurgy; Microstructure; Nanotechnology; Stacking fault energy; Steels; Structural Materials; Surfaces and Interfaces; Tensile strength; Thin Films; Twinning
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-013-2175-z

A Cr-Mn austenitic steel was tensile strained in the temperature range 273 K (0 °C) ≤ T ≤ 473 K (200 °C), to improve the understanding on the role of stacking fault energy (SFE) on the deformation behavior, associated microstructure, and mechanical properties of low-SFE alloys. The failed specimens were studied using X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The SFE of the steel was estimated to vary between ~ 10 to 40 mJ/m 2 at the lowest and highest deformation temperatures, respectively. At the ambient temperatures, the deformation involved martensite transformation ( i.e ., the TRIP effect), moderate deformation-induced twinning, and extended dislocations with wide stacking faults (SFs). The corresponding SF probability of austenite was very high (~10 −2 ). Deformation twinning was most prevalent at 323 K (50 °C), also resulting in the highest uniform elongation at this temperature. Above 323 K (50 °C), the TRIP effect was suppressed and the incidence of twinning decreased due to increasing SFE. At elevated temperatures, fine nano-sized SF ribbons were observed and the SF probability decreased by an order (~10 −3 ). High dislocation densities (~10 15  m −2 ) in austenite were estimated in the entire deformation temperature range. Dislocations had an increasingly screw character up to 323 K (50 °C), thereafter becoming mainly edge. The estimated dislocation and twin densities were found to explain approximately the measured flow stress on the basis of the Taylor equation.