Einfluß der α‐γ‐Umwandlung eines irreversiblen Nickelstahls auf Kristallorientierung und Zugfestigkeit

Wassermann, Günter

doi:10.1002/srin.193300427

Cited by 108 publications

(38 citation statements)

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“…15) Bos and coworkers 16) estimated the interface velocity during the fccto-bcc phase transformation in pure iron in the range of 200-700 m/s using the Johnson-Oh potential. 17) In addition, we have investigated the kinetics of the fcc-bcc heterointerface during the fcc-to-bcc phase transformation with respect to ORs ranging from Nishiyama-Wasserman (N-W) OR 18,19) to Kurdjumow-Sachs (K-S) OR 20) using the Finnis-Sinclair potential 21) and revealed that there are two different propagation behaviors of the heterointerface: a planar propagation for the heterointerface with the N-W or near N-W ORs and a fast needlelike growth after initial planar growth for the heterointerface with the K-S or near K-S ORs. 22,23) The aforementioned MD simulations have captured the kinetics of the heterointerface during unidirectional transformation from the fcc to bcc phase at least qualitatively.…”

Section: Introductionmentioning

confidence: 99%

A Molecular Dynamics Study of Bidirectional Phase Transformation between bcc and fcc Iron

et al. 2011

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Bidirectional phase transformation between bcc and fcc iron is investigated by molecular dynamics simulation using the Finnis-Sinclair potential with a cutoff function in the atomic charge density. It is confirmed that the influence distance (i.e., cutoff distance) of the atomic charge density affects the relative stability between the bcc and fcc phases at high temperature: the bcc is stable at a long cutoff distance and the fcc is stable at a short cutoff distance. Hence, the bidirectional phase transformation across the A3 point comes true by changing the cutoff distance at the A3 point. The propagation of an fcc-bcc heterointerface with a Nishiyama-Wassermann orientation relationship is then examined by relaxation of an fcc-bcc biphasic system at various temperatures. The fcc-to-bcc phase transformation is observed below the A3 point, whereas the heterointerface does not move to any direction at the A3 point. On the other hand, the bcc-to-fcc phase transformation is observed above the A3 point, which has not been successful in previous studies using the original Finnis-Sinclair potential.

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Section: Introductionmentioning

confidence: 99%

A Molecular Dynamics Study of Bidirectional Phase Transformation between bcc and fcc Iron

et al. 2011

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“…Since a bct (body-centered tetragonal)-bcc (body-centered cubic) transformation was proposed as a possible path of the fcc (face-centered cubic)-bcc martensitic transformation by Bain and Dunkiri in 1924, 1) such Bain deformation paths have been widely studied [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] from both experimental and theoretical approaches. For example, transmission electron micrograph images provide much information such as the preferential orientation relationship (OR) 3) and the atomic arrangement 4) at the austenite-martensite interface of iron-based alloys.…”

Section: Introductionmentioning

confidence: 99%

“…Besides iron-based alloys, the structural patterns in the fcc-bcc heterointerface of copper-iron, copper-vanadium 5) and copper-chromium 6) have been studied. In addition, electron backscatter diffraction analysis enables us to accurately determine the orientation relationship of such heterointerfaces, 7) and revealed that close-packed plane of martensite or bainite is not parallel to that of austenite, unlike the Nishiyama-Wasserman (N-W) 8,9) and Kurdjumow-Sachs (K-S) 10) ORs, which are the experimentally commonly observed orientations. Recently, the in situ martensitic phase transformation of iron revealed by four-dimensional electron microscopy 11) has been reported.…”

Section: Introductionmentioning

confidence: 99%

Orientation Relationship in Fcc–Bcc Phase Transformation Kinetics of Iron: a Molecular Dynamics Study

2010

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The kinetics of the (110) bcc //(111) fcc heterointerface of iron during the fcc-bcc phase transformation has been investigated by molecular dynamics simulation. The various orientation relationships (ORs) between Nishiyama-Wasserman (N-W) and Kurdjumow-Sachs (K-S) ORs, which are experimentally observed, were examined. The planar propagation of the fcc-bcc heterointerface was observed in the case of the N-W and near N-W ORs, whereas a fast needlelike growth after initial planar growth was observed in the case of the K-S and near K-S ORs. The transformation started from the matching area of the fcc and bcc lattice and followed the Bain transformation path. It was confirmed that the difference in the matching area of the fcc and bcc lattices at the interface between the N-W and K-S ORs causes the two different propagation behaviors. In addition, the distribution of the atomic stress in the system during phase transformation was examined. The residual atomic stress was distributed toward the [010] bcc direction after the transformation in the case of the N-W OR. The change in the direction of the Bain deformation path during phase transformation caused a fast needlelike growth after the initial planar propagation in the case of the K-S OR.

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“…This necessarily means that there will be 24 variants of the transformation product per austenite grain. As a corollary, simplified descriptions of the orientation relation in terms of Kurdjumov-Sachs 37) and Nishiyama-Wasserman 38,39) are imprecise in detail; thus, the latter orientation would lead to only twelve variants. As far as the author is aware, there has never been experimental confirmation that only twelve variants of martensite can form in a given austenite grain.…”

Section: Calculation Of Texture Due To Displacive Transformationsmentioning

confidence: 99%

Problems in the Calculation of Transformation Texture in Steels

Bhadeshia

2010

ISIJ Int.

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The solid-state decomposition of austenite can lead to a non-random distribution of product crystals. Methods of the quantitative characterisation of this texture are extremely advanced, and there is a deep understanding of the relationship between the texture and macroscopic properties. There remain, however, important barriers to the complete calculation of texture, some of which have not been documented in the published literature. It is the purpose of this review to focus on the difficulties in order to set the scene for further progress. The advent of electron back scatter diffraction has led to an explosion of papers on microscopic aspects of crystal orientations; some of the issues relating to this technique are also described.KEY WORDS: transformation texture; crystallography; steel; martensite; bainite. Consider first the spatial resolution. Using a step size of 2-4 nm might suggest a resolution of that order, but Fig. 1 illustrates the difficulties. The boundaries in this image appear convoluted whereas they are not in reality. The grain marked with an arrow is suggested to have a size of about 8 nm 24) but it is questionable whether this is a real grain or an artefact given the size of the surrounding black regions which are crystallographically unresolved pixels. The grain boundaries themselves appear ragged, with a roughness which is comparable to the suggested 8 nm grain. Such roughness is not likely to be real since and thin film deposition does not normally lead to a bimodal distribution in grain size. 1517Consider now the problem of angular resolution when dealing with steels. The influence of imperfections in causing a spread in orientation well beyond the stated angular resolution of the EBSD instrument is illustrated in Fig. 2(a). Instrumental resolution should be of the order of 0.5°b ut the illustrated spread in the orientation of the single grain of austenite is closer to 10°. There will then be a corresponding spread in the orientations of bainite, as illustrated in Fig. 2(b), even if there is a strictly fixed orientation relationship between the parent (g) and product (a) phases. Products which form by displacive transformations will contain excess dislocations leading to a spread in diffracted intensity. Furthermore, the contribution to the spread from different crystals of bainite or martensite will not be identical given the nonuniform distribution of dislocations, plastic accommodation and the fact that the stress state of the austenite changes as more plates of martensite form. 25) There are many publications in the literature which suggest that there is a spread in the g/a orientation relationship rather than one established by the crystallography of the phases. It is then reasonable to question whether there is a true spread in orientation relationship or one which is caused by a neglect of the fact that the austenite is not a perfect crystal. The measurements implying spread have in some cases been deduced from observations on meteorites, which cool incredibly slowly as they evo...

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Einfluß der α‐γ‐Umwandlung eines irreversiblen Nickelstahls auf Kristallorientierung und Zugfestigkeit

Abstract: Untersuchungen an Drähten aus einer Eisen‐Nickel‐Legierung mit 30 % Ni über den Einfluß der α‐γ‐Umwandlung auf die Kristallorientierung und die Zugfestigkeit sowie über die Festigkeit während der Umwandlung.

Cited by 108 publications

References 0 publications

A Molecular Dynamics Study of Bidirectional Phase Transformation between bcc and fcc Iron

A Molecular Dynamics Study of Bidirectional Phase Transformation between bcc and fcc Iron

Orientation Relationship in Fcc–Bcc Phase Transformation Kinetics of Iron: a Molecular Dynamics Study

Problems in the Calculation of Transformation Texture in Steels

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