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The theory of transformations in metals and alloys
01 Jan 1965-
TL;DR: In this paper, the authors present a general introduction to the theory of transformation kinetics of real metals, including the formation and evolution of martensitic transformations, as well as a theory of dislocations.
Abstract: Part I General introduction. Formal geometry of crystal lattices. The theory of reaction rates. The thermodynamics of irreversable processes. The structure of real metals. Solids solutions. The theory of dislocations. Polycrystalline aggregates. Diffusion in the solid state. The classical theory of nucleation. Theory of thermally activated growth. Formal theory of transformation kinetics. Part II Growth from the vapour phase. Solidification and melting. Polymorphic Changes. Precipitation from supersaturated solid solution. Eutectoidal transformations. Order-disorder transformations. Recovery recrystalisation and grain growth. Deformation twinning. Characteristics of martensic transformations. Crystallography of martensitic transformations. Kinetics of martensitic transformations. Rapid solidification. Bainite steels. Shape memory alloys.
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TL;DR: In this article, the role of surface energy in determining twin width near an austenite was studied, and it was shown that there are two distinct regimes, depending on the relative values of the elastic moduli, surface energy density and grain size.
Abstract: We study the role of surface energy in determining twin width near an austenite—twinned-martensite interface. We find that there are two distinct regimes, depending on the relative values of the elastic moduli, surface energy density and grain size. In the first regime the twin width w is constant, of order L 1/2, where L is the grain size. In the other regime the twin width is not constant; rather, it varies as l 2/3, where l is the distance to the austenite. Most prior analyses have captured only the first regime, and it seems to be the one most commonly observed. However, twin branching consistent with our second regime has been observed in some materials.
237 citations
01 May 1972
TL;DR: In this article, it was shown that the Widmanstatten morphology of upper bainite is inessential to the classification of a eutectoid structure as bainitic ferrite with respect to carbon.
Abstract: The authors debate three topics central to the controversies which have enveloped the bainite reaction ever since it was first recognized as a distinctive mode of austenite decomposition. These include: “what is bainite?”, “the growth mechanism of the ferritic component of bainite”, and “the sources of bainitic carbide precipitation.” RFH concludes that bainite is the product of a shear transformation. Individual bainite plates are suggested to grow substantially more rapidly than volume diffusion-control allows, but a constraint such as the build-up of volume strain energy limits the extent of their growth. This mechanism of growth ensures extensive supersaturation of bainitic ferrite with respect to carbon. Whether or not carbides precipitate in association with bainite plates and whether the carbide is cementite ore, however, is a complex question in competitive reaction kinetics. New experimental evidence is presented to demonstrate thate carbide precipitated in lower bainite dissolves upon heating above the kinetic-B
stemperature in an alloy steel containing 1.5 pct Si. This result is taken to support the existence of the metastable eutectoid reactionγ ⇌ α + e atca 350°C. HIA and KRK define bainite as the product of a nonlamellar eutectoid reaction. On this view, carbide precipitation thus plays an essential, rather than an ancillary role. Development of the Widmanstatten morphology by the ferritic component of bainite is shown to be inessential to the classification of a eutectoid structure as bainite. When this morphology is present, however, it is concluded to grow by the ledge mechanism, without the participation of shear, at rates of the order of or less than those allowed by volume diffusion-control. New experimental evidence is presented to show that the lengthening and thickening kinetics of individual plates within sheaves of upper bainite are consistent with this description. The results of a new calculation indicate that the initial carbon content of bainite plates lies between theα/α + Fe3C) and the extrapolatedα/(α+ γ) phase boundaries, in agreement with expectation from the ledge mechanism of growth.
236 citations
TL;DR: In this paper, the interplay of diffusion and aggregation was studied by Monte Carlo simulations, and it was shown that reactive metals do not have any long-range mobility and are effective diffusion barriers, whereas isolated atoms of less reactive metals diffuse deep into polymers at elevated temperatures.
Abstract: First information on metal diffusion in polymers resulted from surface spectroscopies which mainly provided insight into chemical interactions of metals at polymer surfaces and into their growth mode. Medium energy ion scattering, electron microscopy, atomic force microscopy, and second-harmonic generation revealed a strong tendency of metals of low and intermediate reactivity to form clusters when deposited onto polymers. The interplay of diffusion and aggregation was also studied by Monte Carlo simulations. Metal diffusivities were obtained from radiotracer and Rutherford backscattering measurements. The available results show that reactive metals do not have any long-range mobility and are effective diffusion barriers. In contrast, isolated atoms of less reactive metals diffuse deep into polymers at elevated temperatures. However, the very pronounced aggregation tendency of these metals effectively impedes diffusion unless they are deposited at rates of the order of monolayers per minute or lower. Nevertheless, traces of noble metals always diffuse into polymers during the early stages of metal deposition, whereas no significant diffusion occurs from a continuous metal film. Even noble metal diffusivities are many orders of magnitude smaller than diffusivities of non-reactive gas molecules and largely decoupled from polymer dynamics. This is attributed to a pronounced reduction in the local chain mobility near metal atoms, e.g., by temporary metal-atom-induced crosslinking.
235 citations
TL;DR: In this paper, it has been shown that the contraction of a mortar caused by air entrainment offsets the thermal expansion mismatch stress sufficiently to prevent cracking, and the magnitude of the contraction in air-entrained mortar is shown to account for a reduction of salt scaling damage.
235 citations
TL;DR: In this article, the CO/Pt(100) system was investigated and the mechanism of the adsorbate-induced Pt phase transition was explained, where the CO molecules occupied on top adsorption sites.
Abstract: It is known that clean Pt(100) normally exists in a reconstructed (‘‘hex’’) phase, that a metastable clean unreconstructed phase [the (1×1)] can be prepared, and that during adsorption of CO the hex→(1×1) transition occurs. In this and the following paper, we describe an investigation of the CO/Pt(100) system which clarifies the mechanism of this adsorbate‐induced Pt phase transition. The experimental techniques included fast video‐LEED techniques, thermal desorption spectroscopy, electron energy loss spectroscopy, and work function measurements. Adsorption of CO at low temperature (T≲400 K) is discussed in this paper. CO on (1×1)‐Pt forms a c(2×2) overlayer near and at the ideal coverage of θ=0.5, in which the CO molecules occupy on‐top adsorption sites. Repulsive CO–CO interactions cause this structure to form. CO adsorption on hex‐Pt proceeds via formation of small areas with the same local structure, a c(2×2) layer of CO on (1×1)‐Pt, even when the total coverage of CO is low (0.05<θ<0.5). This compari...
234 citations