The inherent tensile strength of iron

Clatterbuck, D. M.; Chrzan, D. C.; Morris, J. W.

doi:10.1080/095008302317262642

Cited by 50 publications

(30 citation statements)

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“…The extremum of the total energy for the fcc structure is dictated by the symmetry. 73,74,16,30 When performing uniaxial tensile deformation along the ͓001͔ axis of the other materials shown in Table III, no highersymmetry structure is encountered along the tensile part of the deformation path and, therefore, it is not surprising that the values of th /E 001 are considerably different from 0.08 in many cases. From this point of view, it is rather astonishing that th /E 001 ϭ0.078, 0.079, and 0.092 for MoSi 2 , WSi 2 , and TiC, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…In the case of Si atoms, the information about the number and kind of atoms in the coordination spheres is accompanied by the symbols used in Fig. 2͑e͒ for corresponding interatomic bond 30,51 That is, for the bcc metals, the tensile test corresponds to the relaxed Bain's path connecting the bcc and fcc structures and the parameters of the sinusoid are determined by the Young modulus E 001 at low strains ͑curvature͒ and by the structural energy difference between the relaxed fcc and bcc structures, set at the strain corresponding to the relaxed fcc structure ͑this structural energy difference is roughly proportional to E 001 , similarly as the tetragonal shear modulus CЈ is linearly related to the unrelaxed structural energy difference between the bcc and fcc structures 72 ͒. The extremum of the total energy for the fcc structure is dictated by the symmetry.…”

Section: Resultsmentioning

confidence: 99%

“…First calculations have been made without relaxations of the dimensions of a loaded crystal in the directions perpendicular to the loading axis 11 or for unrelaxed shear. 12,13 Relaxed calculations have been performed for TiC, 14,15 tungsten, 16 -18 copper, [19][20][21][22] NiAl, 19,23 aluminum, 24,[20][21][22] ␤-SiC, 25 diamond, 26,27 Si, 27,28 Ge, 27 TiN and HfC, 15 iron, [29][30][31] Mo and Nb, 32 and ␤-Si 3 N 4 . 33 Some calculations have been done for nanowires ͓amorphous Si ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

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Ab initiostudy of the ideal tensile strength and mechanical stability of transition-metal disilicides

2003

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The ideal tensile test in transition metal disilicides MoSi 2 and WSi 2 with a C11 b structure is simulated by ab initio electronic structure calculations using the full-potential linearized augmented plane wave method. The theoretical tensile strength for [001] loading is determined for both disilicides and compared with that of other materials. A full relaxation of all external and one internal structural parameter is performed, and the influence of each relaxation process on energetics and strength of materials studied is investigated. Differences in the behavior of various interatomic bonds including tension-compression asymmetry are analyzed and their origin in connection with the changes of the internal structural parameter is traced. For comparison, the response of bonds in MoSi and CoSi with B2 structure to the [001] loading is also studied. The ideal tensile test in transition metal disilicides MoSi 2 and WSi 2 with a C11 b structure is simulated by ab initio electronic structure calculations using the full-potential linearized augmented plane wave method. The theoretical tensile strength for ͓001͔ loading is determined for both disilicides and compared with that of other materials. A full relaxation of all external and one internal structural parameter is performed, and the influence of each relaxation process on energetics and strength of materials studied is investigated. Differences in the behavior of various interatomic bonds including tension-compression asymmetry are analyzed and their origin in connection with the changes of the internal structural parameter is traced. For comparison, the response of bonds in MoSi and CoSi with B2 structure to the ͓001͔ loading is also studied.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ab initiostudy of the ideal tensile strength and mechanical stability of transition-metal disilicides

2003

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“…In fact, it must do so. It can be shown that the stress developed by the transformation strain of the most favorably oriented martensite lath 10) exceeds the ideal strength of iron, 16) so dislocations or twins would form spontaneously if they did not develop in the normal course of the transformation.…”

Section: The Formation Of Blocks Of Dislocated Martensitementioning

confidence: 99%

Comments on the Microstructure and Properties of Ultrafine Grained Steel

Morris

2008

ISIJ International

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The present paper addresses several connected issues that concern the mechanical properties of ultrafine grained martensitic steels. Recent research, particularly including EBSD studies, has clarified the complex microstructure of dislocated martensitic steels and shown the central importance of martensite blocks, which are subvolumes of laths that share a Bain variant of the parent austenite. The block-and-packet structure of the martensite appears well-designed to minimize the elastic energy introduced during the martensitic transformation. The martensite block is, ordinarily, the effective grain size for both strength and cleavage fracture. However, the role of the block in imparting strength is sensitive to carbon contamination of the block boundaries. To optimize strength carbon should be present; to minimize the ductile-brittle transition temperature it should be eliminated. When fine grain size produces high strength, it also causes low elongation. The elongation can be improved by including mechanisms, such as TRIP, that lower the initial work hardening rate.KEY WORDS: ultrafine-grained steel; martensitic steel; dislocated martensite microstructure; strength; toughness; ductility 1063© 2008 ISIJ Large prior austenite grains are divided into "packets" that are subdivided into "blocks" of martensite laths. When the blocks are small the laths are almost identical in their crystallography; they have the same KS variant. When the blocks are larger they are sometimes found to contain two interleaved KS variants in the specific pairs: V1-V4. V2-V5, V3-V6. When the blocks are interleaved pairs then the packets ordinarily contain three crystallographically distinct blocks, one made from each pair. When the blocks are single-variant the packets contain up to six distinct blocks so that each KS variant is represented. The Structural Composition of Blocks andPackets The microstructure that is described by Maki et al. [3][4][5][6][7][8] can be understood from the elastic theory of phase transformations.The energetic considerations that influence the choice of martensite variant can be developed as follows.9,10) The bcc structure is derived from the fcc by applying the "Bain strain" illustrated in Fig. 2. The fcc structure is compressed by about 23 % along one cube axis and expanded by about 12 % along the perpendicular axes (depending on the volume change) to create bcc. Since there are three choices for the compression axis, the transformation produces three distinct "Bain variants".Of course, a Bain strain that is imposed within the bulk of a fcc crystal would require a prohibitively high elastic energy. As has long been recognized, [11][12][13] that energy is lowered dramatically if the Bain strain is supplemented by a rotation and a small shear to bring the close-packed (011) plane of the bcc product into registry with one of the closepacked {111} planes of the fcc parent, and orient the plane so that low-index crystallographic directions in the plane are also aligned. If we choose the [110] g direction in the (1...

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“…Such crystals can be strong because, in the absence of defects, deformation must occur by the wholesale glide of planes over each other, rather than by the propagation of discontinuities such as dislocations. Micrometre sized crystals of pure iron have achieved strength levels in excess of 10 GPa (Sears et al 1954;Brenner 1956), although in principle the strength can exceed 20 GPa (Clatterbuck et al 2002). The crystals become weaker as they are made larger, because of both the thermodynamically stabilized defects and the accidents of growth.…”

Section: Introductionmentioning

confidence: 99%

Nanostructured bainite

2009

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An alloy system based on iron is described in which it has been possible to create a high density of interfaces by heat treatment alone. The resulting structure consists of a mixture of slender platelets of bainitic ferrite, just 20-40 nm in thickness, embedded in a matrix of carbon-enriched austenite. The rate at which this structure evolves is slow by conventional standards, but this permits components to be made which are large in all three dimensions, with uniform properties throughout. The fundamental mechanisms behind this novel nanostructured steel are reviewed, along with the factors determining its strength, ductility and fracture toughness. It is argued that, although reasonable toughness can be achieved in the context of strength levels exceeding 2000 MPa, the impact toughness remains poor and that it may not be possible to improve this particular parameter.

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The inherent tensile strength of iron

Cited by 50 publications

References 17 publications

Ab initiostudy of the ideal tensile strength and mechanical stability of transition-metal disilicides

Ab initiostudy of the ideal tensile strength and mechanical stability of transition-metal disilicides

Comments on the Microstructure and Properties of Ultrafine Grained Steel

Nanostructured bainite

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