Nanostructure Evolution in an Austenitic Stainless Steel Subjected to Multiple Forging at Ambient Temperature

2010 ◽  
Vol 667-669 ◽  
pp. 553-558 ◽  
Author(s):  
Andrey Belyakov ◽  
Kaneaki Tsuzaki ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Ambient Temperature ◽  
Structural Changes ◽  
Subgrain Size ◽  
Large Strain ◽  
Total Strain ◽  
Large Strains ◽  
Fast Kinetics ◽  
Cumulative Strain

Deformation behavior and structural changes were studied in a 304-type austenitic stainless steel subjected to large strain multiple forging at an ambient temperature. The number of forging passes was 10, leading to the total cumulative strain of 4.0. The yield stress rapidly increased to about 1000 MPa after the first forging pass and then gradually approached a saturation level of about 2000 MPa in large strains. The grain/subgrain size decreased to about 50 nm at total strain of about 2. This grain/subgrain size reduced a little upon further processing; and comprised 35 nm after a total strain of 4.0. The fast kinetics for grain refinement was associated with deformation twinning and strain-induced martensitic transformation. The both of them resulted in fast grain subdivision at relatively small strains.

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.

Deformation Microstructures and Mechanical Properties of an Austenitic Stainless Steel Subjected to Warm Rolling

2016 ◽  
Vol 879 ◽  
pp. 1414-1419 ◽  
Author(s):  
Marina Odnobokova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Structural Changes ◽  
Rolling Direction ◽  
Warm Rolling ◽  
Total Strain ◽  
Large Strains ◽  
Plate Rolling ◽  
Microstructures And Mechanical Properties

The deformation microstructures and mechanical properties of an austenitic stainless steel subjected to warm plate rolling were studied. The warm rolling was carried out at 300°C to different total true strains of 0.5, 1, 2 or 3. The structural changes during warm rolling were characterized by the elongation of original grains towards the rolling direction and the development of spatial network of strain-induced high-angle boundaries leading to the evolution of ultrafine-grained microstructure at sufficiently large strains. The grain refinement was assisted by the development of deformation twinning. After straining to 3, the transverse grain size decreased down to 220 nm in the warm rolled samples. The warm plate rolling resulted in significant strengthening. The microhardness increased from 2910 MPa to 4192 MPa with increase in the total strain from 0.5 to 3. Correspondingly, the yield strength approached 1005 MPa after warm rolling to a total strain of 3.

Ultrafine Grain Evolution in Austenitic Stainless Steel during Large Strain Deformation and Subsequent Annealing

2012 ◽  
Vol 715-716 ◽  
pp. 273-278
Author(s):  
Andrey Belyakov ◽  
Kaneaki Tsuzaki ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Structural Changes ◽  
Volume Fraction ◽  
Subgrain Size ◽  
Large Strain ◽  
Structural Response ◽  
Subsequent Annealing ◽  
Ultrafine Grain ◽  
Average Size

The structural changes in a 304-type austenitic stainless steel during large strain cold rolling and subsequent annealing were studied. The severe deformation resulted in the development of highly elongated grains/subgrains aligned along the rolling axis. The transverse grain/subgrain size rapidly decreased to its minimal value of about 50 nm at relatively small strains of ~1 and then hardly changed upon following deformation. Such a structural response on cold working was associated with multiple twinning resulting in fast grain subdivision. The processing was accompanied by a partial martensitic transformation resulting in a decrease of austenite volume fraction to about 0.35 after straining to ε = 4.0. Isochronal annealing for 30 min was characterised by a gradual coarsening of grains, the average size of which increased to about 200 nm after heating to 800°C. The high elongation of ferrite grains facilitated simultaneous homogeneous nucleation of austenite grains throughout the matrix upon heating; and, therefore, promoted the development of ultrafine grained structure with the size of structural elements well below 1 micron.

Structural Changes in a 9%Cr Creep Resistant Steel during Creep Test

2012 ◽  
Vol 715-716 ◽  
pp. 895-900
Author(s):  
Valeriy Dudko ◽  
Andrey Belyakov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
Rustam Kaibyshev
Keyword(s):  
Structural Changes ◽  
Subgrain Size ◽  
Large Strain ◽  
Particle Growth ◽  
Second Phase ◽  
Second Phase Particles ◽  
Creep Rupture Test ◽  
Lath Structure ◽  
Creep Regime ◽  
Effective Stabilization

Structural changes in a 9%Cr martensitic steel after 1%, 4% creep and creep rupture test at 650°C and stress of 118 MPa were examined. Heat treatment provided the formation of tempered martensite lath structure (TMLS) in the steel. The precipitations of second phase particles along block and lath boundaries provide effective stabilization of the TMSL under annealing/aging condition. This structure hardly changed under creep conditions in grip portion of crept sample. Significant coarsening of both the second phase particles and the martensite laths takes place in neck portion. In addition, the latter ones lose their original morphology and are replaced by large strain-induced subgrains. It should be noted that the increase of subgrain size is in almost direct proportion to the particle growth during the creep to 4% strain. The rapid growth of martesite laths followed by their evolution to deformation subgrains takes place within the tertiary creep regime.

Structural Changes in a 304-Type Austenitic Stainless Steel Processed by Multiple Hot Rolling

2011 ◽  
Vol 409 ◽  
pp. 730-735 ◽  
Author(s):  
Zhanna Yanushkevich ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Hot Rolling ◽  
Structural Changes ◽  
The Other ◽  
Dynamic Processes ◽  
Mean Size ◽  
The Mean

The microstructure evolution and the dynamic processes of grain refinement in a 304-type austenitic stainless steel during multiple calibre hot rolling at temperatures of 700-1000°C were studied. The structural changes are characterized by the elongation of original grains towards the rolling axis and the development of new fine grains, the mean size of which decreases with decreasing the deformation temperature. During multiple rolling at 1000°C, the new grains resulted from the development of discontinuous dynamic recrystallization involving a bulging of frequently corrugated grain boundaries. On the other hand, the new grain boundaries leading to remarkable refinement of original microstructure were developed at temperatures below 800°C as a result of continuous strain-induced reactions.

Recrystallization in Nanostructured Austenitic Stainless Steel

2008 ◽  
Vol 584-586 ◽  
pp. 966-970 ◽  
Author(s):  
Agnieszka T. Krawczynska ◽  
Małgorzata Lewandowska ◽  
Krzysztof Jan Kurzydlowski
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Growth ◽  
Structural Changes ◽  
True Strain ◽  
Equivalent Diameter ◽  
Uniform Microstructure ◽  
Lower Annealing Temperature ◽  
Average Size ◽  
Induced Changes

Recrystallization and grain growth were studied in an austenitic stainless steel 316LVM processed by hydrostatic extrusion (HE) to a total true strain of 2. HE processing produces in this material the microstructure which consists of nanoscale twins on average 19 nm in width and 168 nm in length. The samples after HE were annealed at various temperatures for 1 hour. The structural changes were investigated using TEM. The heat induced changes in nanotwinned austenitic steel are significantly different when compared to the ones in a conventionally deformed material. Microstructural changes take place at lower annealing temperature. Annealing at 600°C brings about a partial a nanostructure reorganization into nanograin of average size 54 nm. An uniform microstructure with nanograins of 68 nm in equivalent diameter was obtained after annealing at 700°C whereas conventional 316LVM steel fully recrystallizes after annealing at 900°C for 1h. Annealing at higher temperatures results in grain growth.

Regularities of Grain Refinement in an Austenitic Stainless Steel during Multiple Warm Working

2013 ◽  
Vol 753 ◽  
pp. 411-416 ◽  
Author(s):  
Andrey Belyakov ◽  
Marina Tikhonova ◽  
Zhanna Yanushkevich ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Structural Changes ◽  
Continuous Dynamic Recrystallization ◽  
Warm Working ◽  
Fine Grain ◽  
Power Law Function ◽  
Continuous Dynamic

The structural changes that are related to the new fine grain development in a chromium-nickel austenitic stainless steel subjected to warm working by means of multiple forging and multiple rolling were studied. The multiple warm working to a total strain of 2 at temperatures of 500-900C resulted in the development of submicrocrystalline structures with mean grain sizes of 300-850 nm, depending on processing conditions. The new fine grains resulted mainly from a kind of continuous reactions, which can be referred to as continuous dynamic recrystallization. Namely, the new grains resulted from a progressive evolution of strain-induced grain boundaries, the number and misorientation of which gradually increased during deformation. In contrast to hot working accompanied by discontinuous dynamic recrystallization, when the dynamic grain size can be expressed by a power law function of temperature compensated strain rate as D ~ Z-0.4, much weaker temperature/strain rate dependence of D ~ Z-0.1was obtained for the warm working.

Grain boundary assembles developed in an austenitic stainless steel during large strain warm working

2012 ◽  
Vol 70 ◽  
pp. 14-20 ◽  
Author(s):  
M. Tikhonova ◽  
R. Kaibyshev ◽  
X. Fang ◽  
W. Wang ◽  
A. Belyakov
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Boundary ◽  
Large Strain ◽  
Warm Working
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