scholarly journals Effect of α′ Martensite Content Induced by Tensile Plastic Prestrain on Hydrogen Transport and Hydrogen Embrittlement of 304L Austenitic Stainless Steel

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 660 ◽  
Author(s):  
Yanfei Wang ◽  
Xuanpei Wu ◽  
Weijie Wu
Keyword(s):  
Hydrogen Embrittlement ◽  
Volume Fraction ◽  
Austenitic Stainless Steels ◽  
Hydrogen Transport ◽  
Hydrogen Diffusivity ◽  
Martensite Content ◽  
Deformation Twins ◽  
316L Steel ◽  
Hydrogen Exposure ◽  
304L Steel

Effects of microstructural changes induced by prestraining on hydrogen transport and hydrogen embrittlement (HE) of austenitic stainless steels were studied by hydrogen precharging and tensile testing. Prestrains higher than 20% at 20 °C significantly enhance the HE of 304L steel, as they induce severe α′ martensite transformation, accelerating hydrogen transport and hydrogen entry during subsequent hydrogen exposure. In contrast, 304L steel prestrained at 50 and 80 °C and 316L steel prestrained at 20 °C exhibit less HE, due to less α′ after prestraining. The increase of dislocations after prestraining has a negligible influence on apparent hydrogen diffusivity compared with pre-existing α′. The deformation twins in heavily prestrained 304L steel can modify HE mechanism by assisting intergranular (IG) fracture. Regardless of temperature and prestrain level, HE and apparent diffusivity ( D app ) increase monotonously with α′ volume fraction ( f α ′ ). D app can be described as log D app = log ( D α ′ s α ′ / s γ ) + log [ f α ′ / ( 1 − f α ′ ) ] for 10 % < f α ′ < 90 % , with D α ′ is diffusivity in α′, s α ′ and s γ are solubility in α′ and austenite, respectively. The two equations can also be applied to these more typical duplex materials containing both BCC and FCC phases.

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.

Microstructural Refinement during Annealing of Plastically Deformed Austenitic Stainless Steels

2007 ◽  
Vol 550 ◽  
pp. 423-428 ◽  
Author(s):  
C. Herrera ◽  
R.L. Plaut ◽  
Angelo Fernando Padilha
Keyword(s):  
Strain Hardening ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Recrystallization Temperature ◽  
Microstructural Refinement ◽  
Aisi 304L ◽  
Strain Induced Martensite ◽  
316L Steel ◽  
Different Temperatures ◽  
304L Steel

The phenomena of strain hardening, strain induced martensite formation, recovery, martensite reversion and recrystallization have been studied in austenitic stainless steels of the AISI 304L and 316L types, after solution annealing, followed by rolling at different temperatures (-196, 25, 100 and 200°C) and subsequent annealing of the worked samples. Strain hardening and the percentage of α’ martensite formed showed strong dependency with the deformation temperature and with the austenite chemical composition. As expected, both strain hardening as well as the amount of the martensite formed was higher in the 304L steel and for lower temperatures. Reversion temperature of the α’ martensite was close to 550°C for both steels, independent of the amount of martensite. The 316L steel presented a higher resistance to recrystallization when compared to the 304L steel. The recrystallization temperature of both steels was about 150°C higher than the α’ phase reversion temperature. Rolling temperature did not influence significantly the recrystallization temperature. Proper thermal and mechanical treatments lead to interesting combinations of mechanical properties in both steels with values such as yield strength YS of about 1000 MPa, with an elongation around 10%.

Internal Reversible Hydrogen Embrittlement and Hydrogen Gas Embrittlement of Austenitic Stainless Steels Based on Type 316

2009 ◽  
Author(s):  
Masaaki Imade ◽  
Lin Zhang ◽  
Mao Wen ◽  
Takashi Iijima ◽  
Seiji Fukuyama ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Room Temperature ◽  
Austenitic Stainless Steels ◽  
Hydrogen Gas ◽  
Hydrogen Transport ◽  
Ni Content ◽  
Hydrogen Segregation ◽  
Slow Strain Rate Technique ◽  
Reversible Hydrogen Embrittlement ◽  
Martensite Structure

The internal reversible hydrogen embrittlement (IRHE) of austenitic Fe(10–20)Ni17Cr2Mo alloys based on type 316 stainless steel was investigated by tests using the slow strain rate technique from 80 to 300 K in comparison with its effect on the hydrogen gas embrittlement (HGE) of the alloys in hydrogen at a pressure of 1 MPa. The IRHE and HGE of the alloys in 70 MPa hydrogen at room temperature was also investigated. At low temperatures, IRHE occurred below a Ni content of 15% (Ni equivalent (Nieq):29%), increased with decreasing temperature, reached a maximum at 200 K, and decreased with further decreasing temperature, similarly to the temperature dependence of HGE. At room temperature, IRHE and HGE were observed below a Ni content of 14% (Nieq:28%) and decreased with increasing Ni content (Nieq). The dependence of HGE on hydrogen pressure increased with decreasing Ni content (Nieq). Hydrogen-induced fracture closely related to the strain-induced α′ martensite structure and twin boundaries mainly occurred for both IRHE and HGE. Dimple ruptures caused by hydrogen segregation occurred in only IRHE at 150 K. The content of strain-induced α′ martensite increased with decreasing temperature and Ni content (Nieq). Thus, the susceptibility to IRHE and HGE depended on Ni content (Nieq). It was concluded that both IRHE and HGE were controlled by the amount of strain-induced α′ martensite above 200 K, whereas they were controlled by the hydrogen transport below 200 K.

Effects of W on hydrogen transport property of Nb45Ti27.5Ni27.5 alloy membranes

2017 ◽  
Vol 31 (34) ◽  
pp. 1750321 ◽  
Author(s):  
Yang Yang ◽  
Dongrong Liu ◽  
Zhifei Zhu ◽  
Guohuai Liu
Keyword(s):  
Hydrogen Embrittlement ◽  
Transport Property ◽  
Volume Fraction ◽  
Hydrogen Permeability ◽  
Hydrogen Solubility ◽  
Hydrogen Transport ◽  
Embrittlement Resistance

Alloying influences of tungsten (W) into Nb[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] on the microstructure, hydrogen solubility, diffusivity, permeability and resistance to hydrogen embrittlement have been investigated. Four experimental temperatures (673, 623, 573 and 523 K) have been used. It is found that the addition of W (5 at.% and 10 at.%) reduces the hydrogen solubility. The constitution of phases is not changed with W addition, whereas volume fraction of primary bcc-niobium (Nb) phase is distinctly reduced for the content of 10 at.% W. The hydrogen permeability and diffusivity increase for Nb[Formula: see text]W[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] only at lower temperatures such as 573 K and 523 K. Addition of 10 at.% W causes an obvious reduction in the permeability and diffusivity. The Nb[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] alloy membrane fractures at 125[Formula: see text]C, while Nb[Formula: see text]W[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] and Nb[Formula: see text]W[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] alloy membranes keep intact when temperature reaches to 100[Formula: see text]C. In comparison with Nb[Formula: see text]Ti[Formula: see text]Ni[Formula: see text], the present research confirms that Nb[Formula: see text]W[Formula: see text]Ti[Formula: see text]Ni[Formula: see text] exhibits an enhancement in hydrogen permeability at relatively lower temperatures and an improvement in embrittlement resistance.

scholarly journals A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
Yngve Bergström ◽  
Ylva Granbom ◽  
Dirk Sterkenburg
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Deformation Process ◽  
Volume Fraction ◽  
High Energy ◽  
Martensite Content ◽  
Plastic Deformation Process ◽  
Deformation Hardening ◽  
Dp Steels ◽  
Ferrite Grain Size

A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

Effect of Inclusions and Precipitates on Hydrogen Embrittlement of Mn-Alloyed Austenitic Stainless Steels

2013 ◽  
pp. n/a-n/a ◽  
Author(s):  
Heikki Pulkkinen ◽  
Suvi Papula ◽  
Olga Todoshchenko ◽  
Juho Talonen ◽  
Hannu Hänninen
Keyword(s):  
Hydrogen Embrittlement ◽  
Stainless Steels ◽  
Austenitic Stainless Steels

Hydrogen Transport and Hydrogen-Assisted Cracking in SUS304 Stainless Steel During Deformation at Low Temperatures

2015 ◽  
Author(s):  
Lin Zhang ◽  
Bai An ◽  
Takashi Iijima ◽  
Chris San Marchi ◽  
Brian Somerday
Keyword(s):  
Stainless Steel ◽  
Hydrogen Embrittlement ◽  
Room Temperature ◽  
Hydrogen Release ◽  
Hydrogen Transport ◽  
Force Microscopy ◽  
Atomic Force ◽  
Strain Induced Martensite ◽  
Hydrogen Assisted Cracking ◽  
Slip Planes

The behaviors of hydrogen transport and hydrogen-assisted cracking in hydrogen-precharged SUS304 austenitic stainless steel sheets in a temperature range from 177 to 298 K are investigated by a combined tensile and hydrogen release experiment as well as magnetic force microscopy (MFM) based on atomic force microscopy (AFM). It is observed that the hydrogen embrittlement increases with decreasing temperature, reaches a maximum at around 218 K, and then decreases with further temperature decrease. The hydrogen release rate increases with increasing strain until fracture at room temperature but remains near zero level at and below 218 K except for some small distinct release peaks. The MFM observations reveal that fracture occurs at phase boundaries along slip planes at room temperature and twin boundaries at 218 K. The role of strain-induced martensite in the hydrogen transport and hydrogen embrittlement is discussed.

scholarly journals Defect and Damage Evolution Quantification in Dynamically-Deformed Metals Using Orientation-Imaging Microscopy

2010 ◽  
Vol 654-656 ◽  
pp. 2297-2302 ◽  
Author(s):  
George T. Gray III ◽  
Veronica Livescu ◽  
Ellen K. Cerreta
Keyword(s):  
Detonation Wave ◽  
Damage Evolution ◽  
Shock Loading ◽  
Volume Fraction ◽  
Orientation Imaging Microscopy ◽  
Electron Back Scatter Diffraction ◽  
Orientation Imaging ◽  
Deformation Twins

Orientation-imaging microscopy offers unique capabilities to quantify the defects and damage evolution occurring in metals following dynamic and shock loading. Examples of the quantification of the types of deformation twins activated, volume fraction of twinning, and damage evolution as a function of shock loading in Ta are presented. Electron back-scatter diffraction (EBSD) examination of the damage evolution in sweeping-detonation-wave shock loading to study spallation in Cu is also presented.

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