scholarly journals On the Strength of a 316L-Type Stainless Steel Subjected to Cold or Warm Rolling Followed by Annealing

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2116 ◽  
Author(s):  
Marina Odnobokova ◽  
Zhanna Yanushkevich ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov
Keyword(s):  
Stainless Steel ◽  
Dislocation Density ◽  
Yield Strength ◽  
Large Strain ◽  
Warm Rolling ◽  
High Yield ◽  
Ultrafine Grained ◽  
Type Stainless Steel ◽  
Power Law Function ◽  
Continuous Recrystallization

The ultrafine-grained microstructures and their effect on the yield strength of a 316L-type austenitic stainless steel processed by large strain cold/warm rolling and subsequent annealing were studied. A kind of continuous recrystallization developed during annealing, resulting in the evolution of uniform ultrafine-grained microstructures with relatively high residual dislocation densities. The development of such microstructure at 973 K led to excellent combination of tensile properties including high yield strength (σ0.2 > 900 MPa) and satisfactory plasticity (δ > 15%). A unique power law function between the annealed grain size and the dislocation density with a dislocation density exponent of −0.5 was obtained for these continuously recrystallized microstructures. A physically justified explanation of the observed structural/substructural strengthening is introduced.

Recrystallization Mechanisms in Severely Deformed Dual-Phase Stainless Steel

2010 ◽  
Vol 638-642 ◽  
pp. 1905-1910 ◽  
Author(s):  
Andrey Belyakov ◽  
Rustam Kaibyshev ◽  
Yuuji Kimura ◽  
Kaneaki Tsuzaki
Keyword(s):  
Stainless Steel ◽  
Large Strain ◽  
Austenite Phase ◽  
The Other ◽  
Dual Phase ◽  
Austenite Stainless Steel ◽  
Ultrafine Grained ◽  
Continuous Recrystallization ◽  
Ultrafine Grained Microstructure ◽  
Structural Recrystallization

The structural recrystallization mechanisms operating in an Fe – 27%Cr – 9% Ni dual-phase (ferrite-austenite) stainless steel after large strain processing to total strain of 4.4 were investigated in the temperature range of 400-700oC. The severe deformation resulted in the development of an ultrafine grained microstructure consisting of highly elongated grains/subgrains with transverse dimensions of 160 nm and 130 nm in ferrite and austenite, respectively. The annealing mechanism operating in ferrite phase was considered as continuous recrystallization, which involved recovery leading to the development of essentially polygonized microstructure. On the other hand, the mechanism of discontinuous nucleation took place at an early recrystallization stage in austenite phase.

Annealing behavior of a ferritic stainless steel subjected to large-strain cold working

2007 ◽  
Vol 22 (11) ◽  
pp. 3042-3051 ◽  
Author(s):  
A. Belyakov ◽  
K. Tsuzaki ◽  
Y. Kimura ◽  
Y. Mishima
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Cold Working ◽  
Large Strain ◽  
Recrystallization Behavior ◽  
Bar Rolling ◽  
Annealing Behavior ◽  
Ultrafine Grained ◽  
Continuous Recrystallization ◽  
Cold Strain

Mechanisms of microstructure evolution during annealing after cold working were studied in an Fe-15%Cr ferritic stainless steel, which was processed by bar rolling/swaging to various total strains ranging from 1.0 to 7.3 at ambient temperature. Two types of recrystallization behavior were observed depending on the cold strain. An ordinary primary (discontinuous) recrystallization developed in the samples processed to conventional strains of 1.0–2.0. On the other hand, rapid recovery at early annealing resulted in ultrafine-grained microstructures in the larger strained samples that continuously coarsened on further annealing. Such annealing behavior was considered as continuous recrystallization.

Effect of Hydrogen Isotopes on the Fracture Toughness Properties of Types 316L and 304L Stainless Steel Forgings

2019 ◽  
Author(s):  
Michael J. Morgan
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Yield Strength ◽  
316L Stainless Steel ◽  
Large Strain ◽  
Hydrogen Isotopes ◽  
High Yield ◽  
304L Stainless Steel ◽  
Type 316L ◽  
Type 316L Stainless Steel

Abstract Forged stainless steels are commonly used for the containment of hydrogen isotopes and fracture toughness properties are needed for structural integrity assessments. In this study, the effects of hydrogen and tritium precharging on the fracture-toughness properties of Types 316L and 304L stainless steel forgings were measured. The purpose of the study was to evaluate hydrogen and tritium effects on fracture toughness properties of: (1) Type 316 stainless steel stem-shaped and cup shaped forgings; and (2) Type 304L cylindrical block forgings with two different yield strengths. Arc-shaped fracture toughness specimens were cut from the forgings and precharged by exposing the specimens to hydrogen or tritium gas at 623K and 34.5 MPa. Tritium precharged specimens were aged at 193 K for 45 months prior to testing to build-in helium-3 from tritium decay. In the as-received condition, the J-Integral fracture toughness of the stem, cup, and block forgings were very high and exceeded 1200 kJ/m2 on average. The fracture toughness of specimens cut from the low yield strength Type 304L stainless steel block forging had the highest fracture toughness values and Type 316L stainless steel cup forging had the lowest. The reduced fracture toughness values were attributed to the large strain required to produce the cup forging and its high yield strength. Hydrogen precharging reduced the fracture toughness of the stem, cup, and block forgings to values between 34%–51% of a baseline value which was taken to be the fracture toughness value of the low yield strength block forging. Tritium precharging reduced the fracture-toughness values more than hydrogen precharging because of the effects of helium from radioactive decay of tritium. The fracture-toughness properties of tritium-precharged forgings ranged from 12% to 23% of the baseline values. In general, Type 316L stainless steel was more resistant to toughness reductions by hydrogen or tritium (and decay helium) than Type 304L stainless steel. Yield strength had only minor effects on fracture toughness for the precharged steels.

Recovery in 15%Cr Ferritic Stainless Steel after Large Strain Deformation

2007 ◽  
Vol 558-559 ◽  
pp. 119-124
Author(s):  
Andrey Belyakov ◽  
Kaneaki Tsuzaki ◽  
Yoshisato Kimura ◽  
Yoshinao Mishima
Keyword(s):  
Stainless Steel ◽  
Low Temperature ◽  
Dislocation Density ◽  
Ambient Temperature ◽  
Ferritic Stainless Steel ◽  
Vickers Hardness ◽  
Subgrain Size ◽  
Large Strain ◽  
Internal Stresses ◽  
Cumulative Strain

15%Cr ferritic stainless steel was machined in rectangular samples and then processed by multiple forging to a total cumulative strain of 7.2 at an ambient temperature. The large strain deformation resulted in almost equiaxed submicrocrystalline structure with a mean grain/subgrain size of 230 nm and about 2.2×1014 m-2 dislocation density in grain/subgrain interiors. The annealing at a relatively low temperature of 500oC did not lead to any discontinuous recrystallizations. The grain/subgrain size and the interior dislocation density slightly changed to 240 nm and 2.1×1014 m-2, respectively, after annealing for 30 min, while the Vickers hardness decreased from 3140 MPa in the as-processed state to 2900 MPa. This annealing softening was attributed to remarkable release (by 50%) of internal stresses, which are associated with a non-equilibrium character of strain-induced grain/subgrain boundaries.

scholarly journals A 2.9 GPa Strength Nano-Grained and Nano-Precipitated 304L-Type Austenitic Stainless Steel

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5382
Author(s):  
Congcong Du ◽  
Guoying Liu ◽  
Baoru Sun ◽  
Shengwei Xin ◽  
Tongde Shen
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Yield Strength ◽  
Average Particle Size ◽  
Coarse Grained ◽  
Average Particle ◽  
Dispersion Strengthening ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Bulk Nanocrystalline

Austenitic stainless steel has high potential as nuclear and engineering materials, but it is often coarse grained and has relatively low yield strength, typically 200–400 MPa. We prepared a bulk nanocrystalline lanthanum-doped 304L austenitic stainless steel alloy by a novel technique that combines mechanical alloying and high-pressure sintering. The achieved alloy has an average grain size of 30 ± 12 nm and contains a high density (~1024 m−3) of lanthanum-enriched nanoprecipitates with an average particle size of approx. 4 nm, leading to strong grain boundary strengthening and dispersion strengthening effects, respectively. The yield strength of nano-grained and nano-precipitated stainless steel reaches 2.9 GPa, which well exceeds that of ultrafine-grained (100–1000 nm) and nano-grained (<100 nm) stainless steels prepared by other techniques developed in recent decades. The strategy to combine nano-grain strengthening and nanoprecipitation strengthening should be generally applicable to developing other ultra-strong metallic alloys.

On Structural Mechanism of Continuous Recrystallization in Ferritic Stainless Steel after Large Strain Processing

2006 ◽  
Vol 503-504 ◽  
pp. 323-328 ◽  
Author(s):  
Andrey Belyakov ◽  
Yuuji Kimura ◽  
Kaneaki Tsuzaki
Keyword(s):  
Stainless Steel ◽  
Grain Growth ◽  
Ferritic Stainless Steel ◽  
Large Strain ◽  
Large Fraction ◽  
Bar Rolling ◽  
Structural Mechanism ◽  
Annealing Behaviour ◽  
Recovery Processes ◽  
Continuous Recrystallization

The annealing behaviour of an Fe – 22%Cr – 3%Ni ferritic stainless steel processed by bar rolling/swaging to total strain of 4.4 at an ambient temperature was studied in the temperature range of 400 ~ 700oC. The annealing behaviour was characterised by the development of continuous recrystallization involving recovery processes followed by a normal grain growth. The large strain deformation caused the very fast recovery resulting in the development of almost equiaxed polygonized microstructure in place of the highly elongated deformation (sub)grains. The polygonization development was accompanied by some increase in the transverse (sub)grain size and the formation of many low-angle subboundaries. The latter ones could be composed from the dislocations, which were emitted by the strain-induced deformation (sub)boundaries. In spite of relatively large fraction of low-angle subboundaries, such polygonized microstructure was essentially stable against a discontinuous grain coarsening. Upon further annealing, therefore, the microstructure evolution was considered as a normal grain growth.

scholarly journals Peculiarities of DRX in a Highly-Alloyed Austenitic Stainless Steel

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4004
Author(s):  
Pavel Dolzhenko ◽  
Marina Tikhonova ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Flow Stress ◽  
Austenitic Stainless Steel ◽  
Dislocation Density ◽  
Strain Rate ◽  
Power Law ◽  
Peak Flow ◽  
Power Law Function ◽  
Grain Orientation Spread

The features of discontinuous dynamic recrystallization (DRX) in a highly-alloyed austenitic stainless steel were studied at temperatures of 800 °C to 1100 °C. Hot deformation accompanied by DRX was characterized by an activation energy of 415 kJ/mol. The frequency of the sequential DRX cycles depended on the deformation conditions; and the largest fraction of DRX grains with small grain orientation spread below 1° was observed at a temperature of around 1000 °C and a strain rate of about 10−3 s−1. The following power law relationships were obtained for DRX grain size (DDRX) and dislocation density (ρ) vs. temperature-compensated strain rate (Z) or peak flow stress (σP): DDRX ~ Z−0.25, ρ ~ Z0.1, σP ~ DDRX−0.9, σP ~ ρ1.4. The latter, i.e., σP ~ ρ1.4, was valid in the flow stress range below 300 MPa and changed to σP ~ ρ0.5 on increasing the stress. The obtained dependencies suggest a unique power law function between the dislocation density and the DRX grain size with an exponent of −0.5.

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