Microstructural evolution of a Titanium-stabilized 15Cr-15Ni steel

Kesternich, W.; Meertens, D.

doi:10.1016/0001-6160(86)90217-8

Cited by 69 publications

(33 citation statements)

References 20 publications

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“…Similar suppression of helium bubble growth was also seen from positron lifetime studies on alpha irradiated Ni-Ti alloys [12]. It is known form TEM studies on Ti-bearing steels that helium bubble formation is suppressed and is associated with nano scale TiC formation in the intra grain regions [13]. In order to understand positron behaviour in irradiated Ti-steels, we have carried out detailed studies to understand the TiC precipitation behaviour prior to irradiation [14][15][16].…”

Section: Helium Bubblessupporting

confidence: 55%

“…In the TiC precipitation regime where the positron lifetime show an increase from 120 ps to about 155 ps, the behaviour is not in line with simple thermally activated process. This explained as due to the intimate involvement of dislocations to act as nucleation centres for TiC precipitation [13][14][15]. The limited temperature dependence of dislocation controlled TiC precipitation is governed by apparent activation energy of 1.6 eV [15].…”

Section: Tic Precipitatesmentioning

confidence: 99%

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Defect evolution in steels: Insights from positron studies

Rajaraman

Amarendra

Sundar

2009

Phys. Status Solidi (c)

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Positron annihilation studies on austentic and ferritic/martensitic and oxide‐dispersion steels are highlighted so as to emphasize the sensitivity of the technique to defect annealing as well as precipitates. The results obtained on austenitic D9 steels are discussed with a view to emphasize the role of small TiC precipitates in the matrix, which play a critical role in void‐swelling behaviour. Further, the role of Ti/C ratio as well as minor alloying elements on swelling behaviour is discussed. The current focus of research is on the use of nanoclusters in ODS alloys towards the suppression of void formation under irradiation. Recent results on the investigation on nano Yttria particles in Fe – model oxide dispersion ferritic steel, are presented with supporting ab‐initio lifetime calculations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Helium Bubblessupporting

confidence: 55%

Section: Tic Precipitatesmentioning

confidence: 99%

Defect evolution in steels: Insights from positron studies

Rajaraman

Amarendra

Sundar

2009

Phys. Status Solidi (c)

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“…Notice that in this alloy the precipitation of intermetallic phases and of M 6 C did not occur. 29,128) The primary phase TiN, (Ti, Mo)C and Ti 4 C 2 S 2 , that remained after the solution annealing are not shown in the diagram. The mentioned low boron content was enough to cause a boride precipitation.…”

Section: Time-temperature-precipitation Diagramsmentioning

confidence: 99%

Decomposition of Austenite in Austenitic Stainless Steels

2002

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Austenitic stainless steels are probably the most important class of corrosion resistant metallic materials. In order to attain their good corrosion properties they rely essentially on two factors: a high chromium content that is responsible for the protective oxide film layer and a high nickel content that is responsible for the steel to remain austenitic. Thus the base composition is normally a Fe-Cr-Ni alloy. In practice the situation is much more complex with several other elements being present, such as, Mo, Mn, C, N among others. In such a complex situation one almost never has a single austenite phase but other phases invariably form. Those phases are, with few exceptions, undesirable and they can be detrimental to the corrosion and mechanical properties. It is therefore of considerable importance to study the formation of such phases. In this work the decomposition of austenite in austenitic stainless steels is reviewed in detail. First the binary equilibrium diagrams relevant to the system Fe-Cr-Ni are briefly presented as well as other diagrams, such as the Schaeffler diagram, that traditionally have been used to predict the phases present in these steels as a function of composition. Secondly the precipitation of carbides and intermetallic phases is presented in detail including nucleation sites and orientation relationships and the influence of several factors such as composition, previous deformation and solution annealing temperature. Next, the occurrence of other constituents such as nitrides, sulfides and borides is discussed. TTT diagrams are also briefly presented. Finally the formation of martensite in these steels is discussed.KEY WORDS: austenitic stainless steel; precipitation behaviour; carbides; intermetallic compounds; TTT diagram; strain induced martensite. Phase DiagramsPhase diagrams are important to predict the phases present in the austenitic stainless steels. Nevertheless they have limitations due to the complexity of multicomponent thermodynamic calculations and also due to the transformation kinetics that may prevent the attainment of the equilibrium phases. Regarding the first limitation, the number of relevant components is often more than five and published diagrams are rarely found to contain more than four components. As to the second limitation, the diffusion of alloying elements in austenite can be very slow and the precipitation of certain intermetallic compounds can take thousands of hours. Equilibrium DiagramsIn this section the most relevant features of the binary diagrams 3,4) Fe-Cr, Fe-Ni, Cr-Ni, Fe-Mo, Fe-Ti, Ni-Ti, FeNb, Fe-Mn and Fe-Si are considered. Next the Fe-Cr-Ni and Fe-Cr-Mo ternary diagrams and the quaternary FeCr-Ni-Mo diagram are discussed. The individual characteristics of each phase will be presented later in this review.The two main features of the Fe-Cr diagram, shown in Fig. 1, which are relevant to austenitic stainless steels, are the ferrite stabilizing character of Cr and the presence of sigma (s) phase.The Fe-Ni diagram clearly shows the strong ...

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“…This recrystallization resistance is important for the performance of this steel as a cladding material for fast breeder nuclear reactors. [4][5][6] The transmission electron micrograph of Fig. 6 illustrates the softening by recovery and the appearance of sub-grains at 800°C in this steel.…”

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confidence: 94%

“…1.4970 steel has an extremely low M d temperature and deformation induced martensite has never been detected. [4][5][6] An explanation for such a behaviour is that nickel has an accentuated effect in increasing the SFE, 44) and in suppressing the formation of DIM. 22) With respect to the increase in aЈ-martensite formation with the increase in strain rate 11,24) it is important to mention that the sample or test sample temperature can increase during deformation.…”

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confidence: 99%

Annealing of Cold-worked Austenitic Stainless Steels.

2003

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This article reviews the phenomena involved during the annealing of cold worked austenitic stainless steels. Initially the cold worked state is discussed, with special emphasis on the formation of deformation induced martensites. Following, the phenomena of martensite reversion, recovery, recrystallization and grain growth are discussed. The interactions between primary recrystallization and precipitation and between precipitate dissolution and secondary recrystallization are dealt with in detail. Finally, the textures resulting from hot and cold working, and from primary and secondary recrystallization, are presented.KEY WORDS: austenitic stainless steels; work hardening; recovery; recrystallization; grain growth; texture.cold working can be correlated to a lower SFE. 39) Deformation twinning is also dependent on SFE and grain size. Low SFE and large grain size favor deformation twinning. Recent work 40) has shown that deformation twin initiation requires a critical deformation (critical dislocation density). The SFE has an indirect effect by increasing dislocation density and strain hardening in low-SFE fcc metals and alloys. 40) Another aspect that must be remembered is that SFE of the ASSs increases with deformation temperature. 41) In summary, depending on the value of the SFE, two different microstructures may be observed in the cold worked ASSs: for a high SFE, a cellular dislocation distribution without DIM and, for a low SFE, a planar dislocation distribution containing DIM. It is worthy of note that deformation bands can be found in both.In terms of recrystallization, the lower is the SFE, keeping all others variables constant, the larger will be the stored energy during deformation and the corresponding driving force for recrystallization. This subject will be discussed later on in greater detail.ASSs are commonly considered to be materials having a low SFE. Actually the SFE of this class of steels are within quite a large range. [42][43][44][45][46][47] Fig. 2(b)). Several interesting features can observed in this figure. Microstructural analysis using optical microscopy, as shown in Fig. 2(a) for a high SFE ASS, does not allow differentiation between high and low SFE austenitic stainless steels after cold working. Furthermore, at the transmission electron microscopy scale deformation bands may be seen eventually (compare Figs. 2(b) and 2(c)). Monteiro and Kestenbach 49) using transmission electron microscopy observed that dislocation substructure is orientation sensitive, i.e., individual grains develop different substructures, according to their specific orientation and the orientation of their neighbours.As previously mentioned, two types of martensite may occur in the ASSs, namely: aЈ-(bcc, ferromagnetic) and e-(hcp, paramagnetic). The typical lattice parameters are: a aЈ ϭ0.2872 nm and a e ϭ0.2532 nm; c e ϭ0.4114 nm Assuming 50) a g ϭ0.3585 nm, we may conclude that the g→aЈ transformation leads to volume increase of about ISIJ International, Vol. 43 (2003) where the contents are in wt%. Since ...

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Microstructural evolution of a Titanium-stabilized 15Cr-15Ni steel

Cited by 69 publications

References 20 publications

Defect evolution in steels: Insights from positron studies

Defect evolution in steels: Insights from positron studies

Decomposition of Austenite in Austenitic Stainless Steels

Annealing of Cold-worked Austenitic Stainless Steels.

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