scholarly journals Effect of thermo-mechanical processes on microstructure evolution in austenitic stainless steels

2019 ◽  
Vol 24 ◽  
pp. 110-117
Author(s):  
Giuseppe Napoli ◽  
Orlando Di Pietro ◽  
Giulia Stornelli ◽  
Andrea Di Schino
Keyword(s):  
Microstructure Evolution ◽  
Stainless Steels ◽  
Austenitic Stainless Steels

scholarly journals Microstructure/Mechanical Characterization of Plasma Nitrided Fine-Grain Austenitic Stainless Steels in Low Temperature

Nitrogen ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 244-258
Author(s):  
Abdelrahman Farghali ◽  
Tatsuhiko Aizawa ◽  
Tomoaki Yoshino
Keyword(s):  
Microstructure Evolution ◽  
Stainless Steels ◽  
Nitrided Layer ◽  
Austenitic Stainless Steels ◽  
Uniaxial Tensile ◽  
Two Phase ◽  
Solute Content ◽  
Fine Grained ◽  
Applied Loading ◽  
Uniaxial Tensile Testing

Fine-grained austenitic stainless steels (FGSS) were plasma nitrided below 700 K to describe their microstructure evolution during the nitrogen supersaturation process and to investigate the post-stressing effect on the microstructure and mechanical properties of nitrided FGSS. Normal- and fine-grained AISI304 plates were nitrided at 623 K and 673 K to investigate the grain size effect on the nitrogen supersaturation process as well as the microstructure evolution during the nitriding process. Fine-grained AISI316 (FGSS316) wires were nitrided at 623 K to demonstrate that their outer surfaces were uniformly nitrided to have the same two-phase, refined microstructure with high nitrogen solute content. This nitrided FGSS316 wire had a core structure where the original FGSS316 core matrix was bound by the nitrided FGSS316 layer. The nitrided wire had higher stiffness, ultimate strength, and elongation in the uniaxial tensile testing than its un-nitrided wires. The core microstructure was refined and homogenized by this applied loading together with an increase of nitrided layer hardness.

scholarly journals Microstructure Evolution during Annealing Treatment of Austenitic Stainless Steels

2012 ◽  
Vol 715-716 ◽  
pp. 913-913 ◽  
Author(s):  
Clara Herrera ◽  
Angelo Fernando Padilha ◽  
R.L. Plaut
Keyword(s):  
Grain Size ◽  
Microstructure Evolution ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Thickness Reduction ◽  
Recrystallization Temperature ◽  
Delta Ferrite ◽  
Aisi 304L ◽  
316L Steel ◽  
304L Steel

Austenitic stainless steels of the AISI 304 and 316 grades, amongst over other hundred compositions of stainless steels available in the market, are the most frequently used ones worldwide. They are selected for numerous applications due to their favorable combination of characteristics such as low price, moderate to good corrosion resistance, excellent ductility and toughness along with good weldability. Their major limitation is in the yield strength, which is relatively low (about 200 MPa), in the annealed condition. Through cold working, this value can be easily multiplied by a factor of up to six, however ductility drops. The cold worked sub-structure of the austenitic stainless steels is formed by a planar array of dislocations and strain induced martensites, α (BCC) and ε (HCP). The microstructure evolution of austenitic stainless steels, AISI 304L and 316L, during cold rolling and subsequent annealing was studied (maximum thickness reduction - 90%). Samples were initially solution annealed at 1100°C for one hour with subsequent water quenched. Following, they have been cold rolled at room temperature, with cold reductions varying between 10 and 90%. After rolling, samples with approximately 90% thickness reduction have been submitted to annealing treatments in order to study martensite reversion, recovery and recrystallization. Annealing treatments have been performed between 200 and 900°C, with 100°C interval for one hour. The resulting microstructures were investigated by optical microscopy, scanning electron microscopy (with EBSD), magnetic measurements and hardness evaluation. As received (hot rolled) austenitic stainless steel sheet presented recrystallized equiaxial grains with austenite and islands of delta ferrite, in larger quantities mainly in the centre of the sheet. The solution annealing at 1100°C for one hour eliminated delta ferrite. During rolling, the austenite partially transforms into α martensite. The 50% αmartensite reversion temperature is close to 550°C for both steels. This temperature is practically independent of the amount of αmartensite present in the steel. The 50% recrystallization temperature of the 304L steel is lower than that of the 316L steel, about 700 and 800°C, respectively. The 316L steel shows a higher recrystallization resistance, due to its higher SFE and lower storage deformation energy than the 304L steel. Recrystallization temperature is about 150°C higher that the αmartensite reversion temperature. The percentage of αmartensite has a strong influence on the recrystallized grain size, the higher the percentage of this phase the smaller will be the grain size.

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