Influence of prior deformation temperature on strain induced martensite formation and its effect on the tensile strengthening behaviour of type 304 SS studied by XRDLPA

The Low-Cycle Fatigue Behavior, Microstructure Evolution, and Life Prediction of SS304: Influence of Temperature

“…However, when the deformation temperature exceeds Md (the maximum temperature martensitic phase transformation occurs) at 322 K [ 38 ], the strain-induced martensitic phase transformation process is inhibited [ 39 , 40 ]. Below the Md temperature, plastic deformation causes parallel shear bands to appear in sub-stable austenitic, and with increasing strain, cross-shear bands develop where martensite nucleation occurs [ 41 ]. Compared to RT, the tensile curves at 300 °C and 650 °C have weaker strength and ductility since the bcc-martensite is unfortunately lost as an effective barrier to dislocation movement in the FCC-austenite phase [ 42 ].…”

Investigation on Creep Deformation and Age Strengthening Behavior of 304 Stainless Steel under High Stress Levels

“…And dislocations are also accumulated at the grain boundaries. At the same time, as the creep strain continues to increase, there will be part of the austenite transformation to 𝜀-martensite, and then to 𝛼 -martensite transformation, or directly into 𝛼 -martensite [6], resulting in a rapid increase in the content of 𝛼 -martensite. It can be 8a), which strengthens the austenite phase in the parent material and produces a mechanically stabilized phenomenon.…”

“…And dislocations are also accumulated at the grain boundaries. At the same time, as the creep strain continues to increase, there will be part of the austenite transformation to ε-martensite, and then to α ′ -martensite transformation, or directly into α ′ -martensite [6], resulting in a rapid increase in the content of α ′ -martensite. It can be seen that α ′ -martensite inserts across the austenite crystal (Figure 8d), and these locations are the dense areas of dislocation rings or the areas where twins exist (Figure 8c).…”

“…For example, SpaceX's rocket fuel tanks are made of 304 SS, which significantly improves productivity and reduces costs. 304 SS is a metastable austenitic stainless steel (MASS) where deformation below M d temperature can induce transformation from the fcc austenite phase (γ) to the bcc martensite phase (α ′ ) [6]. M d temperature is a temperature above which deformation does not induce martensitic transformation.…”

“…Various studies of MASS plastically deformed at room temperature have shown that dissociated dislocations, laminar dislocations, deformation twins and ε-martensite with an hcp structure occur within the austenite [7][8][9][10]. These microstructures, which can be collectively referred to as shear zones, tend to occur during plastic deformation of materials with low-stacking fault energy, and α'-martensite tends to nucleate and grow at the location of such shear zones and their intersections [6][7][8][9][10][11]. At the same time, 304 SS is also a transformation-related induced plasticity (TRIP) steel.…”