Microstructure Evolution in a 304-Type Austenitic Stainless Steel during Multidirectional Forging at Ambient Temperature

2014 ◽  
Vol 783-786 ◽  
pp. 831-836 ◽  
Author(s):  
Alla Kipelova ◽  
Marina Odnobokova ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
Volume Fraction ◽  
True Strain ◽  
Nanocrystalline Structure ◽  
Multidirectional Forging ◽  
Average Size ◽  
Structural Mechanisms

The formation of nanocrystalline structure in a 304-type austenitic stainless steel during multidirectional forging (MDF) at room temperature was investigated. Initial coarse austenite grains with an average size of 50 μm were refined to about 80 nm by martensitic transformation during MDF to a total true strain of 2 and remained unchanged upon further deformation up to a strain of 4. The volume fraction of martensite achieved ~0.9 after forging to a strain of 1.6. The MDF at room temperature was accompanied by a significant hardening of the 304-type steel. The microhardness and the flow stress increased during forging and approached their saturations on the levels of about 5 GPa and 1.7 GPa, respectively, after total true strain of 2. The structural mechanisms responsible for microstructure evolution during severe deformation are discussed.

scholarly journals Effect of Rolling Temperature on Microstructure Evolution and Mechanical Properties of AISI316LN Austenitic Stainless Steel

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1557 ◽  
Author(s):  
Yi Xiong ◽  
Yun Yue ◽  
Tiantian He ◽  
Yan Lu ◽  
Fengzhang Ren ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
Volume Fraction ◽  
Parent Phase ◽  
Rolling Temperature ◽  
Tensile Fracture ◽  
Transformation Rate

The impacts of rolling temperature on phase transformations and mechanical properties were investigated for AISI 316LN austenitic stainless steel subjected to rolling at cryogenic and room temperatures. The microstructure evolution and the mechanical properties were investigated by means of optical, scanning, and transmission electron microscopy, an X-ray diffractometer, microhardness tester, and tensile testing system. Results showed that strain-induced martensitic transformation occurred at both deformation temperatures, and the martensite volume fraction increased with the deformation. Compared with room temperature rolling, cryorolling substantially enhanced the martensite transformation rate. At 50% deformation, it yielded the same fraction as the room temperature counterpart at 90% strain, while at 70%, it totally transformed the austenite to martensite. The strength and hardness of the stainless steel increased remarkably with the deformation, but the corresponding elongation decreased dramatically. Meanwhile, the tensile fracture morphology changed from a typical ductile rupture to a mixture of ductile and quasi-cleavage fracture. The phase transformation and deformation mechanisms differed at two temperatures, with the martensite deformation contributing to the former, and austenite deformation to the latter. Orientations between the transformed martensite and its parent phase followed the K–S (Kurdjumov–Sachs) relationship.

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.

Anomalous Property Evolution during Annealing in HPTed SUS 304 Austenitic Stainless Steel

2010 ◽  
Vol 667-669 ◽  
pp. 589-592
Author(s):  
Innocent Shuro ◽  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Ho Hung Kuo ◽  
Hong Cai Wang
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Room Temperature ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Peak Hardness ◽  
Scanning Calorimetry ◽  
Matrix Deformation ◽  
Magnetization Saturation ◽  
304 Austenitic Stainless Steel

SUS 304 austenitic stainless steel (ASS) was deformed by high pressure torsion (HPT) to obtain 100% volume fraction of martensite (α') from a fully austenitic (γ) matrix. Deformation caused an increase in hardness (Hv) from 1.6 GPa in the as annealed state to 6.4 GPa　after HPT. Deformed samples were then annealed in the range 200 – 600oC and peak hardness of 7.8 GPa was observed after annealing at 400oC for 1 hour. Differential scanning calorimetry (DSC) and electrical resistivity tests showed that the deformed alloy undergoes a two stage phase transformation on heating from room temperature up to 700oC. The first stage of transformation was associated with hardening behavior while the second one which is reverse α' → γ transformation resulted in a reduction in hardness. Annealing at 400oC after deformation was found to increase the magnetization saturation (Msat) values.

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.

Magnetic Characterization of SUS316L Deformed by High Pressure Torsion

2011 ◽  
Vol 239-242 ◽  
pp. 1300-1303
Author(s):  
Hong Cai Wang ◽  
Minoru Umemoto ◽  
Innocent Shuro ◽  
Yoshikazu Todaka ◽  
Ho Hung Kuo
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Stainless Steel ◽  
Phase Transformation ◽  
Austenitic Stainless Steel ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Austenitic Matrix ◽  
Magnetic Characterization

SUS316L austenitic stainless steel was subjected to severe plastic deformation (SPD) by the method of high pressure torsion (HPT). From a fully austenitic matrix (γ), HPT resulted in phase transformation from g®a¢. The largest volume fraction of 70% a¢ was obtained at 0.2 revolutions per minute (rpm) while was limited to 3% at 5rpm. Pre-straining of g by HPT at 5rpm decreases the volume fraction of a¢ obtained by HPT at 0.2rpm. By HPT at 5rpm, a¢®g reverse transformation was observed for a¢ produced by HPT at 0.2rpm.

Effects of Deformation Mode on Resistivity Curve Used for Estimating Martensite Induced in Stainless Steel

2010 ◽  
Vol 638-642 ◽  
pp. 2992-2997 ◽  
Author(s):  
Hidefumi Date
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Linear Relation ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Deformation Mode ◽  
Transformation Process ◽  
Martensite Formation ◽  
Austenitic Phase ◽  
Ε Phase

The martensite induced in three types of austenitic stainless steel, which indicate the different stability of the austenitic phase (γ), were estimated by the resistivity measured during the tensile deformation or compressive deformation at the temperatures 77, 187 and 293 K. The resistivity curves were strongly dependent on the deformation mode. The volume fraction of the martensite (α’) was also affected by the deformation mode. The ε phase, which is the precursor of the martensite and is induced from the commencement of the deformation, decreased the resistivity. However, lots of defects generated by the deformation-induced martensite increased the resistivity. The experimental facts and the results shown by the modified parallelepiped model suggested a complicated transformation process depending on each deformation mode. The results shown by the model also suggested a linear relation between the resistivity and the martensite volume at the region of the martensite formation. The fact denoted that the resistivity is mostly not controlled by the austenite, ε phase and martensite, but by the defects induced due to the deformation-induced martensite.

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