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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 paper, the coarsening mechanism of equiaxed grains in the semisolid state of aluminum 7075 alloy, treated via strain induced melting activation process, was investigated.
Abstract: In the present study, the coarsening mechanism of equiaxed grains in the semisolid state of aluminum 7075 alloy, treated via strain induced melting activation process, was investigated. The kinetics of equiaxed grain growth in the semisolid state of the experimental alloy was determined. The results revealed that when the holding temperature increased, the coarsening rate constant (K) showed a precipitously increasing character in the range of 590–610 °C. This was attributed to the extensive effect of the coalescence mechanism on the grain growth at the high solid fractions. By further increasing the holding temperature to 620 and 625 °C (increasing the liquid fraction), the effect of coalescence on the grain growth appeared to be weakened, that is, although there was a slight decrease at 620 °C, a gently increasing character could be generally supposed. Severe segregation of Zn and Cu alloying elements at grain boundaries and intragranular droplets was detected at 620 and 625 °C after 15 and 10 min, respectively.
52 citations
TL;DR: In this paper, the hot-flow behavior of Inconel 718 subjected to delta processing (DP) was analyzed, where a classic dynamic recrystallization (DRX) behavior was observed in the flow curves, which is typical of low medium stacking fault energy (SFE) alloys.
52 citations
TL;DR: In this article, the influence of Yb 3+ content on structural evolution and fluorescence properties of oxyfluoride glass ceramics containing LaF 3 nano-crystals was systematically investigated.
52 citations
25 Jan 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the TTP diagram for the Fe 2 Nb-Laves phase of stainless steel is presented, showing that at about 600°C nucleation takes place on dislocations but above 750°C, grain boundary nucleation is dominant.
Abstract: Electrolytic extraction followed by XRD analysis of precipitates after isothermal annealing of an AISI 441 ferritic stainless steel between 600 and 850 °C produced the time–temperature–precipitation (TTP) diagram for the Fe 2 Nb-Laves phase. The TTP diagram shows two classical C noses, the first one between 750 and 825 °C and the second one, estimated to be close to 650–675 °C. TEM analyses show two independent nucleation mechanisms, i.e. at about 600 °C nucleation takes place on dislocations but above 750 °C, grain boundary nucleation is dominant. The measured solvus temperature of 875 °C for Fe 2 Nb in this steel is 50 °C higher than predicted by Thermo-Calc ® . Kinetic modelling at 800 °C agreed well with the experimental results for a surface energy of 0.435 J m −2 and an initial particle center-to-center separation distance on grain boundaries of about 0.2 μm.
52 citations
TL;DR: In this article, a single stage polymorphic-type transformation of the amorphous phase forming a Ti2CuNi crystalline phase was observed, and the activation energy for such a single-stage crystallization was determined by Kissinger analysis.
Abstract: Crystallization behavior of the Ti50Ni25Cu25 alloy was studied by means of scanning and isothermal differential calorimetry, X-ray diffraction, conventional and high-resolution transmission electron microscopy. A single stage polymorphic-type transformation of the amorphous phase forming a Ti2CuNi crystalline phase was observed. The activation energy for such a single stage crystallization of the amorphous phase was determined by Kissinger analysis. Kinetics of the crystallization was analyzed on the basis of Johnson-Mehl-Avrami equation and discussed regarding to the value of Avrami exponent obtained. Relatively high average value of Avrami exponent of 5.5 at the range from 702 to 709 K suggests nucleation with an increasing nucleation rate.
52 citations