Effect of strain rate on stress-strain behavior of alloy 309 and 304L austenitic stainless steel

Abstract

The effect of strain rate on stress-strain behavior of austenitic stainless steel 309 and 304L was investigated. Tensile tests were conducted at room temperature at strain rates ranging from 1.25 ϫ 10 Ϫ4 s Ϫ1 to 400 s Ϫ1 . The evolution of volume fraction martensite that formed during plastic deformation was measured with X-ray diffraction and characterized with light microscopy. Alloy 304L was found to transform readily with strain, with martensite nucleating on slip bands and at slip band intersections. Alloy 309 did not exhibit strain-induced transformation. Variations in ductility and strength with strain rate are explained in terms of the competition between hardening, from the martensitic transformation and a positive strain rate sensitivity, and softening due to deformational heating. Existing models used to predict the increase in volume fraction martensite with strain were examined and modified to fit the experimental data of this study as well as recent data for alloys 304 and 301LN obtained from the literature.

Dynamic necking in materials with strain induced martensitic transformation

“…Among the metallic materials having these specific features, steel grades showing Strain Induced Martensitic Transformation (SIMT) are widely used for energy absorption in crash or blast protection applications (Andersson, 2005;Schleyer, 2005, 2006;Bleck et al, 2005;Sato et al, 2013). Their ability to transform from the initial face-centered cubic austenite phase γ to body-centered cubic martensite α′ during plastic deformation is comparable to a dynamic composite effect and causes a remarkable hardening (Lichtenfeld et al, 2006;Oliver et al, 2007;Dan et al, 2008). Multiphase TRansformation Induced Plasticity (TRIP) steels and metastable austenitic grades are representative examples of steels exhibiting SIMT.…”

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

“…Austenite can be transformed to marteniste in different ways (Lichtenfeld et al, 2006;Curtze et al, 2009). Spontaneous transformation is dri ven by the difference in the chemical free energy of the two phases, when the material is cooled below the martensite start temperature M s .…”

“…Magee's mechanism accounts for the preferred martensitic plates orientation caused by the loads applied, causing a non nil resultant of the shearing micro stresses and an average macro scopic shape change. These effects enhance the work hardenability of the steel, delay the onset of necking, and thus improve formability (Lichtenfeld et al, 2006;Dan et al, 2008;Oliver et al, 2007).…”

PDC Ic Weld Failure Evaluation and Resolution

“…The reference data do not indicate strain rate / crosshead speed which can affect strength by about 5 ksi as well as elongation with faster rates generally resulting in higher strength and lower ductility measurements (9,10). Sample size can also affect the measured properties.…”