Microstructural Analyses of Modified-Ausformed Medium-Carbon Steel with High Resistance to Hydrogen Embrittlement by Atomic Force Microscopy

Hayakawa, Masayuki; Terasaki, Satoshi; Hara, Toru; Tsuzaki, Kaneaki; Matsuoka, Saburo

doi:10.2320/jinstmet1952.66.7_745

Cited by 31 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[24][25][26] This can be explained in terms of higher density of dislocations, 25) denser distribution of carbide particles, 25,26) and finer block structure 27) in the AF steels. The results in Figs.…”

Section: Tensile Propertiesmentioning

confidence: 99%

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Kimura

Inoue

2016

ISIJ International

View full text Add to dashboard Cite

Recently, we have reported that ultrafine elongated grain (UFEG) structures with strong < 110 > //rolling direction (RD) fiber textures, which are similar to those in cold drawn steel wires, [4][5][6] are particularly effective in toughening of medium-carbon low-alloy steel bars.7-11) A 0.4C-2Si-1Cr-1Mo steel (mass%) with an UFEG structure had an average yield strength (σ y ) of 1.84 GPa and an average Charpy V-notch absorbed energy (vE) of 226 J at room temperature. 7,9,11) Furthermore, the UFEG structure steels were observed to exhibit an inverse temperature dependence of toughness at subzero temperatures, as a consequence of delamination, in which cracks branched and propagated in the longitudinal direction of impact bars.7-11) The vE of the UFEG structure steels increased as the temperature decreased, in contrast to a ductile-to-brittle transition of conventional ultra-high strength steels. It has also been clarified that the microstructural factors controlling the occurrence A 0.4C-2Cr-1Mo-2Ni steel (in mass%) was austenitized at 1 123 K, followed by ausforming (AF) using multi-pass caliber rolling with a rolling reduction of 74%. The AF samples were subsequently tempered at 773 K and deformed by multi-pass caliber rolling (i.e. warm tempforming, WTF) with a rolling reduction of 46%. Their microstructures and mechanical properties were investigated and compared to those of the quenched and tempered samples (non-AF samples) which were subjected to the sequent WTF with rolling reductions of 46% and 74%. The WTF with rolling reductions ranging 46 to 74% resulted in the strengthening and toughening of the AF and non-AF samples through the evolution of anisotropic and ultrafine grain structures with strong < 110 > //rolling direction (RD) fiber textures. The AF sample demonstrated the faster kinetics of the microstructural changes, i.e. refinement in the transverse grain size and development of highly elongated grains than the non-AF sample. As a result, the AF sample exhibited a better combination of ultra-high strength and toughness than the non-AF sample, when compared at the rolling reduction of 46%. The combined effect of AF and WTF was especially pronounced in the enhancement of toughness resulting from delamination.

show abstract

Section: Tensile Propertiesmentioning

confidence: 99%

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Kimura

Inoue

2016

ISIJ International

View full text Add to dashboard Cite

show abstract

“…Precipitates on boundaries have been shown to play important roles in intergranular fracture mechanisms of tempered martensitic steels. 14,15,[19][20][21] For this reason, the authors quantified precipitate distribution separately for the entire microstructure and prior grain boundaries (intergranular).…”

Section: Changes In Microstructure Caused By Creep-fatigue 321 Distmentioning

confidence: 99%

“…The distribution of carbide precipitates in grain interiors and grain boundaries was quantitatively analyzed in terms of both number and size by specifying the locations of prior grain boundaries in a large visual field. [13][14][15] The authors also applied microstructural analytical methods to ferritic heat-resisting steels that were originally developed for carbon steels. Electropolished surfaces of 9 to 12 mass% Cr ferritic steel were observed under a field emission-type scanning electron microscope (FE-SEM), and thin films of these specimens were observed under a TEM.…”

Section: Introductionmentioning

confidence: 99%

Observation of Multi-Scale Structure for a Creep-Fatigued Ferritic 12Cr-2W Steel

et al. 2004

Self Cite

View full text Add to dashboard Cite

Microstructural analyses by field emission-type scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were performed on a ferritic heat-resisting steel that contained 12 mass% chromium and 2 mass% tungsten to characterize its multi-scale structure, consisting of prior austenite grains, packets, blocks, subgrains and precipitates. The size distributions of the blocks, subgrains and precipitates were quantitatively evaluated before and after a creep-fatigue test to relate them to their creep-fatigue property. Our results showed that the occupancy of precipitates on prior austenite grain boundaries increased markedly and subgrains became coarse during the creep-fatigue test, while the block size did not change. It is suggested that the growth of grain boundary precipitates and coarse subgrains plays an important role in the intergranular fracture mechanism caused by creep-fatigue.

show abstract

“…Using atomic force microscopy (AFM), Hayakawa et al 6,7) observed in detail the microstructures of two types of low-alloy JIS-SCM440 steel-modified-ausformed, and quenched and tempered. They found that in the modified-ausformed steel, the density of cementite at the prior austenitic grain boundaries decreased owing to the refinement of martensitic blocks.…”

Section: Introductionmentioning

confidence: 99%

Suppression of Hydrogen-Assisted Fatigue Crack Growth in Carbon Steels

2013

Self Cite

View full text Add to dashboard Cite

Carbon steels with high resistance to hydrogen-assisted fatigue crack growth were successfully produced by the addition of a carbideforming element and the refinement of ferrite grain size. In carbon steels containing vanadium, titanium, or niobium, fine carbide (VC, TiC, or NbC, respectively) precipitation and the refinement of grain size below 1 µm were achieved by caliber rolling at 833 K. Hydrogen charging increased the fatigue crack growth rate in standard JIS-S45C carbon steel to about 25 times that in uncharged steels. In contrast, in carbon steels containing carbide-forming elements, hydrogen-assisted fatigue crack growth was either absent or at most two times faster than that in uncharged steels.

show abstract

Microstructural Analyses of Modified-Ausformed Medium-Carbon Steel with High Resistance to Hydrogen Embrittlement by Atomic Force Microscopy

Abstract: H d) and time to failure (t f) for the modified ausformed and tempered (MAQT) martensite and the conventional QT martensite with a tensile strength of 1580 MPa 5) .

Cited by 31 publications

References 0 publications

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Combined Effect of Ausforming and Warm Tempforming on the Strength and Toughness of An Ultra-High Strength Steel

Observation of Multi-Scale Structure for a Creep-Fatigued Ferritic 12Cr-2W Steel

Suppression of Hydrogen-Assisted Fatigue Crack Growth in Carbon Steels

Contact Info

Product

Resources

About