Optimal Chemical Composition in Fe-Cr-Ni Alloys for Ultra Grain Refining by Reversion of Deformation Induced Martensite

Takaki, Setsuo; Tanimoto, Seiji; Tomimura, Kouki; Tokunaga, Youichi

doi:10.2355/tetsutohagane1955.74.6_1052

Cited by 9 publications

(5 citation statements)

References 7 publications

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“…Fine piercing is an essential process in metal forming for accurate drilling of holes and for fine blanking. In the last decade, metastable austenitic stainless steel type AISI304 with fine grains has been developed by [18][19][20]; the effects of fine crystallographic structure on the elasto-plastic deformation have been closely studied in [21][22][23]. Figure 5 shows three metastable austenitic stainless steel AISI304 sheets with the thickness of 100 μm, where the grain size was reduced by rolling process from the normal-grained sheet with the average grain size (D) of 7.…”

Section: Crystallographic Change By Piercingmentioning

confidence: 99%

Micro-/Nano-Structuring in Stainless Steels by Metal Forming and Materials Processing

Aizawa¹,

Shiratori²,

Komatsu³

2020

Electron Crystallography

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Austenitic stainless steel type AISI304 sheets and plates as well as finegrained type AISI316 (FGSS316) substrates and wires were employed as a work material in the intense rolling, the piercing and the plasma nitriding. AISI304 sheet after intense rolling had textured microstructure in the rolling direction. Crystallographic state changed itself to have distorted polycrystalline state along the shearing plane by piercing, with the strain induced phase transformation. FGSS316 substrates were plasma nitrided at 623 K for 14.4 ks to have two-phase fine nanostructure with the average grain size of 100 nm as a surface layer with the thickness of 30 μm. FGSS316 wires were also plasma nitrided at the same conditions to form the nitrided surface down to the depth of 30 μm. This nitrided wire was further uniaxially loaded in tensile to attain more homogeneously nitrided surface nano-structure and to form the austenitic and martensitic fiber structure aligned in the tensile direction. Each crystallographic structure intrinsic to metals and metallic alloys was tailored to have preferable micro−/nano-structured cells by metal forming and nitrogen supersaturation. The crystallographic change by metal forming in a priori and posterior to nitriding was discussed to find out a new way for materials design.

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Section: Crystallographic Change By Piercingmentioning

confidence: 99%

Micro-/Nano-Structuring in Stainless Steels by Metal Forming and Materials Processing

Aizawa¹,

Shiratori²,

Komatsu³

2020

Electron Crystallography

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“…The ultra-fine grain austenitic stainless steel used in this study was produced by a thermo-mechanical treatment which had been developed by Takaki et al [19,20]. Figure 1 shows the conditions of the thermo-mechanical treatment.…”

Section: Introductionmentioning

confidence: 99%

412 Fatigue properties of ultra-fine grain austenitic stainless steel and effect of hydrogen

Mori

Kubota

Macadre

2014

The Proceedings of Conference of Kyushu Branch

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The fatigue properties of ultra-fine grain austenitic steel (UFG16-10), which has a 1 µm average grain size, were studied as part of the project aimed at the development of high-strength low-cost stainless steels for hydrogen service. The fatigue properties of the UFG16-10 were compared with that of a coarse grain material with the same chemical composition (CG16-10) and two kinds of commercial steels, JIS SUS316 and JIS SUH660. The fatigue strength of the UFG16-10 was 2.8 times higher than that of the CG16-10. The effect of hydrogen on the fatigue limit of the UFG16-10 was not significant. However, the fatigue life of the UFG16-10 was reduced by hydrogen in the short life regime. In the fatigue crack growth test, the UFG16-10 showed a good crack growth resistance that was equivalent to that of the SUH660 and significantly higher than that of the SUS316. However, the crack growth rate was significantly accelerated by hydrogen. The cause of the hydrogen-assisted fatigue crack growth of the UFG16-10 was transformation of the microstructure at the crack tip from austenite to strain-induced martensite. This was also the cause of the reduced fatigue life of the hydrogen-charged UFG16-10.

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“…1. 2,3) The area enclosed by the three lines gives the chemical composition satisfying the three conditions. However, the 18Cr-9Ni steel being out of the area (shown by 'x') was selected as a specimen because the purpose of this study is to use a small amount of untransformed martensite which is retained after reversion for suppressing grain growth of the ultrafine grained austenite during superplastic deformation.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

“…The following conditions must be satisfied for obtaining the metastable austenitic steel with ultrafine grained structure: 2,3) (1) Deformation-induced martensitic single structure is formed by cold rolling at room temperature. (2) Austenitic single structure is formed after reversion of the deformation-induced martensite at around 900 K. (3) The reversed austenite does not undergo martensitic transformation on cooling.…”

Section: Materials and Experimental Proceduresmentioning

confidence: 99%

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Effect of Initial Microstructure on Superplasticity in Ultrafine Grained 18Cr-9Ni Stainless Steel

Tsuchiyama¹,

Nakamura²,

Hidaka³

et al. 2004

Mater. Trans.

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Ultrafine grained austenitic structure was obtained in 18Cr-9Ni stainless steel by thermomechanical treatment using reversion from deformation-induced martensite. The superplastic deformation behavior was investigated at 923 K for the steels containing various amounts of retained martensite particles in the initial structure before tensile testing. The retained martensite was effective for suppressing grain growth of austenite and necessary for the superplasticity although it was thermodinamically unstable phase and gradually decreased its volume fraction with superplastic deformation. Therefore, the superplastic elongation was strongly dependent on the initial volume fraction of the retained martensite. The total superplastic elongation was enlarged with increasing the initial amount of martensite, and the maximum elongation of about 270% was obtained when the volume fraction was controlled to be around 10 vol%. However, the increase in elongation was leveled off in the range above 15 vol% martensite. The effect of the retained martensite on the superplasticiy was discussed in connection with the changes in volume fraction of the martensite, austenite grain size and deformation mechanism.

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Optimal Chemical Composition in Fe-Cr-Ni Alloys for Ultra Grain Refining by Reversion of Deformation Induced Martensite

Cited by 9 publications

References 7 publications

Micro-/Nano-Structuring in Stainless Steels by Metal Forming and Materials Processing

Micro-/Nano-Structuring in Stainless Steels by Metal Forming and Materials Processing

412 Fatigue properties of ultra-fine grain austenitic stainless steel and effect of hydrogen

Effect of Initial Microstructure on Superplasticity in Ultrafine Grained 18Cr-9Ni Stainless Steel

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