Articles de revues : « Phase transformation interfaces »

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Farahani, Hussein, Gerrit Zijlstra, Maria Giuseppina Mecozzi, Václav Ocelík, Jeff Th M. De Hosson et Sybrand van der Zwaag. « In Situ High-Temperature EBSD and 3D Phase Field Studies of the Austenite–Ferrite Transformation in a Medium Mn Steel ». Microscopy and Microanalysis 25, n^o 3 (12 avril 2019) : 639–55. http://dx.doi.org/10.1017/s143192761900031x.

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AbstractIn this research, in situ high-temperature electron backscattered diffraction (EBSD) mapping is applied to record and analyze the migration of the α/γ interfaces during cyclic austenite–ferrite phase transformations in a medium manganese steel. The experimental study is supplemented with related 3D phase field (PF) simulations to better understand the 2D EBSD observations in the context of the 3D transformation events taking place below the surface. The in situ EBSD observations and PF simulations show an overall transformation behavior qualitatively similar to that measured in dilatometry. The behavior and kinetics of individual austenite–ferrite interfaces during the transformation is found to have a wide scatter around the average interface behavior deduced on the basis of the dilatometric measurements. The trajectories of selected characteristic interfaces are analyzed in detail and yield insight into the effect of local conditions in the vicinity of interfaces on their motion, as well as the misguiding effects of 2D observations of processes taking place in 3D.

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Fischer, F. D., N. K. Simha et J. Svoboda. « Kinetics of Diffusional Phase Transformation in Multicomponent Elastic-Plastic Materials ». Journal of Engineering Materials and Technology 125, n^o 3 (1 juillet 2003) : 266–76. http://dx.doi.org/10.1115/1.1586939.

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The goal of this paper is to derive a micromechanics framework to study the kinetics of transformation due to interface migration in elastic-plastic materials. Both coherent and incoherent interfaces as well as interstitial and substitutional atomic diffusion are considered, and diffusional transformations are contrasted with martensitic ones. Assuming the same dissipation for the rearrangement of all substitutional components and no dissipation due to diffusion in an interface in the case of a multicomponent diffusional transformation, we show that the chemical driving force of the interface motion is represented by the jump in the chemical potential of the lattice forming constituent. Next, the mechanical driving force is shown to have the same form for both coherent and frictionless (sliding) interfaces in an elastic-plastic material. Using micromechanics arguments we show that the dissipation and consequently the average mechanical driving force at the interface due to transformation in a microregion can be estimated in terms of the bulk fields. By combining the chemical and mechanical parts, we obtain the kinetic equation for the volume fraction of the transformed phase due to a multicomponent diffusional transformation. Finally, the communication between individual microregions and the macroscale is expressed by proper parameters and initial as well as boundary conditions. This concept can be implemented into standard frameworks of computational mechanics.

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Fang, Hui, Qianyu Tang, Qingyu Zhang, Yiming Fan, Shiyan Pan, Markus Rettenmayr et Mingfang Zhu. « Simulation of the Peritectic Phase Transition in Fe-C Alloys ». Materials 15, n^o 2 (11 janvier 2022) : 537. http://dx.doi.org/10.3390/ma15020537.

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In this work, a multi-phase cellular automaton (CA) model is extended for the quantitative simulation of peritectic phase transition. First, the effects of cooling rate/supersaturation and temperature on the peritectic transformation kinetics in Fe-C alloys are investigated by utilizing the present CA model. The CA simulations show that supersaturations in the parent phases (liquid and δ-ferrite) increase the L/γ interface growth velocity remarkably, but tinily for the δ/γ interface migration velocity. There exists a transition supersaturation for isothermal transformations, at which the growth rates of the two interfaces are equal. The transition supersaturation is found to increase with decreasing temperature. Microstructural evolution at different cooling rates during peritectic transformation is simulated using the experimental conditions. At low cooling rates, the δ/γ interface propagates at a higher velocity than the L/γ interface. At high cooling rates, however, the γ-phase grows more into the L-phase with a cellular morphology. Then, the proposed CA model is applied to simulate the microstructural evolution during peritectic reaction. It is observed that the γ-phase propagates along the L/δ interface and finally encircles the δ-phase. Meanwhile, the intervenient γ-phase grows in thickness through peritectic transformation. The CA simulations are compared reasonably well with the experimental data and analytical calculations.

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Zhang, Hongliang, Jianqi Xi, Ranran Su, Xuanxin Hu, Jun Young Kim, Shuguang Wei, Chenyu Zhang, Liqun Shi et Izabela Szlufarska. « Enhancing the phase stability of ceramics under radiation via multilayer engineering ». Science Advances 7, n^o 26 (juin 2021) : eabg7678. http://dx.doi.org/10.1126/sciadv.abg7678.

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In metallic systems, increasing the density of interfaces has been shown to be a promising strategy for annealing defects introduced during irradiation. The role of interfaces during irradiation of ceramics is more unclear because of the complex defect energy landscape that exists in these materials. Here, we report the effects of interfaces on radiation-induced phase transformation and chemical composition changes in SiC-Ti3SiC2-TiCx multilayer materials based on combined transmission electron microscopy (TEM) analysis and first-principles calculations. We found that the undesirable phase transformation of Ti3SiC2 is substantially enhanced near the SiC/Ti3SiC2 interface, and it is suppressed near the Ti3SiC2/TiC interface. The results have been explained by ab initio calculations of trends in defect segregation to the above interfaces. Our finding suggests that the phase stability of Ti3SiC2 under irradiation can be improved by adding TiCx, and it demonstrates that, in ceramics, interfaces are not necessarily beneficial to radiation resistance.

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Weatherly, G. C. « Interfaces and precipitation ». Proceedings, annual meeting, Electron Microscopy Society of America 50, n^o 1 (août 1992) : 224–25. http://dx.doi.org/10.1017/s0424820100121521.

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An important class of alloy transformation involves the precipitation of a body-centred cubic phase in a close packed cubic or hexagonal matrix (or vice-versa). In the past ten years, numerous investigations have demonstrated that the precipitate grows as a lath or needle-shaped particle, with the growth direction of the axis of the particle parallel to an invariant line of the phase transformation. Although there are an infinite number of potential invariant lines in such a transformation, commonly one observes that the growth direction is close to the common close-packed directions e.g. <110>f and <111>b, with a rational or near-rational orientation relationship between the two phases. These observations can be rationalized by invoking the geometric principles embodied in Bollmann's O-lattice theory or by appealing to the minimization of strain energy principle associated with the set(s) of misfit dislocations lying parallel to the invariant line. Figure 1 shows an example of this characteristic morphology of a lath of γ (face—centred) precipitated in a matrix of α (body-centred) in a two-phase stainless steel. The lath is bounded by well-developed facet planes_(see Fig. 1) with a growth direction about 5° from the common close packed [111]α, [101]γ directions. Sets of misfit dislocations and steps are visible at the (416)α and (275)α facet planes.

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Zhang, Hengzhong, et Jillian F. Banfield. « Phase transformation of nanocrystalline anatase-to-rutile via combined interface and surface nucleation ». Journal of Materials Research 15, n^o 2 (février 2000) : 437–48. http://dx.doi.org/10.1557/jmr.2000.0067.

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The kinetics of phase transformation of nanocrystalline anatase samples was studied using x-ray diffraction at temperatures ranging from 600 to 1150 °C. Kinetic data were analyzed with an interface nucleation model and a newly proposed kinetic model for combined interface and surface nucleation. Results revealed that the activation energy of nucleation is size dependent. In anatase samples with denser particle packing, rutile nucleates primarily at interfaces between contacting anatase particles. In anatase samples with less dense particle packing, rutile nucleates at both interfaces and free surfaces of anatase particles. The predominant nucleation mode may change from interface nucleation at low temperatures to surface nucleation at intermediate temperatures and to bulk nucleation at very high temperatures. Alumina particles dispersed among the anatase particles can effectively reduce the probability of interface nucleation at all temperatures.

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Zhang, Wen-Zheng. « Reproducible Orientation Relationships Developed from Phase Transformations—Role of Interfaces ». Crystals 10, n^o 11 (16 novembre 2020) : 1042. http://dx.doi.org/10.3390/cryst10111042.

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The orientation relationship (OR) between phases related by a phase transformation is often reproducible. This study interprets and predicts the reproducible ORs with a two-stage approach. The initial OR formed at the nucleation stage tends to allow a periodic structure of a preferred state to form in the interface. A matching correspondence of either a one-to-one or n-to-m nature can be specified in the periodic structure. An initial OR will become the final reproducible OR if there is no misfit. Otherwise, a reproducible OR developed at the growth stage tends to permit a singular dislocation structure to form in an interface where the preferred state must be sustained locally. The actual change in the OR is subject to the given material system and the phase-transformation condition. Various singular dislocation structures and their constraints on the ORs are analyzed, with thermodynamics and kinetics applied conceptually. The resulting ORs can be specified by following one or more Δg parallelism rules. A set of workable steps is provided to facilitate the interpretation of observed reproducible ORs. Some unsolved problems are identified, which call for further studies that can quantitatively combine the thermodynamics, kinetics and crystallography of phase transformations.

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Howe, James M. « Atomic Structure, Composition, Mechanisms and Dynamics of Transformation Interfaces in Diffusional Phase Transformations ». Materials Transactions, JIM 39, n^o 1 (1998) : 3–23. http://dx.doi.org/10.2320/matertrans1989.39.3.

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Rettenmayr, Markus, Oleg Kashin et Stephanie Lippmann. « Simulation of Liquid Film Migration during Melting ». Materials Science Forum 790-791 (mai 2014) : 127–32. http://dx.doi.org/10.4028/www.scientific.net/msf.790-791.127.

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Melting of a single-phase polycrystalline material is known to start by the formation of liquid films at the surface and at grain boundaries. The internal liquid films are not necessarily quiescent, but can migrate to avoid/reduce supersaturation in the solid phase. The migration is discussed in the literature to be governed by coherency strains of the solid/liquid interface, by concentration gradients in the liquid or by concentration gradients in the solid phase. A phase transformation model for diffusional phase transformations considering interface thermodynamics (possible deviations from local deviations) has been put up to describe the migration of the solid/liquid (trailing) and the liquid/solid (leading) interfaces of the liquid film. New experimental results on melting in a temperature gradient in combination with simulation calculations reveal that concentration fluctuations in the liquid phase trigger the liquid film migration and determine the migration direction, until after a short time in the order of microseconds the process is governed by diffusion in the solid phase.

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Zhang, J. X., et H. Q. Ye. « Deformation-induced α2 ↔ γ phase transformation in a Ti–48Al–2Cr alloy ». Journal of Materials Research 15, n^o 10 (octobre 2000) : 2145–50. http://dx.doi.org/10.1557/jmr.2000.0309.

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The structure of γ–α2 interfaces in deformed Ti–48Al–2Cr alloy was analyzed by high-resolution transmission electron microscopy (HREM) and image simulations. Growth of γ–TiAl plate in α2–Ti3Al phase was found to be a result of a ledge mechanism consisting of Shockley partial dislocations on alternate (0001)α2 planes. The height of the ledges was always a multiple of two (0001)α2 planes. The γ → α2 phase transformation was also an interface-related process. Large ledges of six close packed planes (111)γ high were often observed at the γ–α2 interface. Every large ledge consisted of six Shockley partial dislocations that originated from the γ–a2 interfacial lattice misfit. The movement of these partial dislocations accomplished the transformation of γ → α2 phase. Comparing the experimental and simulated HREM image, it was found that atomic reordering appears during the deformation-induced γ↔α2 transformation.

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Liu, Binbin, Zhu Zhu, Caiyun Liu, Yao Wang et Feng Ye. « Effect of Inserted Ti Layers on the Phase Transformation of Al/Ni Multilayer Foils ». Coatings 12, n^o 4 (26 mars 2022) : 453. http://dx.doi.org/10.3390/coatings12040453.

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The thin Ti layers were inserted in the interfaces of base Al/Ni multilayer foils to form the Al/Ti/Ni/Ti (ATNT) foils through magnetron deposition. Al and Ni were determined in the as-deposited foils, while the absence of Ti was due to the strongly textured polycrystalline structure. TEM analysis implied an asymmetric interface structure between the Ni/Ti/Al interfaces and Al/Ti/Ni interfaces. After annealing at 473 K and 573 K for 3 h, the phase composition was the same as the initial state, which changed to be Al3Ni2, Ni3(AlTi), Ni and a small amount of Al3Ti when the treating temperature reached 673 K. Further increasing the annealing temperature to 773 K and 873 K leads to the appearance of stable AlNi. The obtained results implied that the inserted Ti layers impeded atomic interdiffusion and the formation of Al3Ni at the early stage, but had less impact on the final products. This further indicated that adding the inserted transition layer provides a reference to balance the storage stability and reaction performance of Al/Ni foils with regard to the applications.

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Fleck, Michael, Felix Schleifer et Patrick Zimbrod. « Frictionless Motion of Diffuse Interfaces by Sharp Phase-Field Modeling ». Crystals 12, n^o 10 (21 octobre 2022) : 1496. http://dx.doi.org/10.3390/cryst12101496.

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Diffuse interface descriptions offer many advantages for the modeling of microstructure evolution. However, the numerical representation of moving diffuse interfaces on discrete numerical grids involves spurious grid friction, which limits the overall performance of the model in many respects. Interestingly, this intricate and detrimental effect can be overcome in finite difference (FD) and fast Fourier transformation (FFT)-based implementations by employing the so-called sharp phase-field method (SPFM). The key idea is to restore the discretization-induced broken translational invariance (TI) in the discrete phase-field equation by using analytic properties of the equilibrium interface profile. We prove that this method can indeed eliminate spurious grid friction in the three-dimensional space. Focusing on homogeneous driving forces, we quantitatively evaluate the impact of spurious grid friction on the overall operational performance of different phase-field models. We show that the SPFM provides superior degrees of interface isotropy with respect to energy and kinetics. The latter property enables the frictionless motion of arbitrarily oriented diffuse interfaces on a fixed 3D grid.

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Shen, X. P., B. N. Yao, Z. R. Liu, D. Legut, H. J. Zhang et R. F. Zhang. « Mechanistic insights into interface-facilitated dislocation nucleation and phase transformation at semicoherent bimetal interfaces ». International Journal of Plasticity 146 (novembre 2021) : 103105. http://dx.doi.org/10.1016/j.ijplas.2021.103105.

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Li, Xianchao. « Secondary-phase Transformation of Duplex Stainless Steels during Industrial Manufacturing ». Journal of Physics : Conference Series 2541, n^o 1 (1 juillet 2023) : 012030. http://dx.doi.org/10.1088/1742-6596/2541/1/012030.

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Abstract A new type of lean S32205 duplex stainless steel was studied on its secondary phase formation during industrial manufacturing. Different from the common S32205 duplex stainless steels, such lean S32205 duplex stainless steels contain more carbon and nitrogen elements, which promotes the formation of Cr2N and Cr23C6 secondary precipitations. The secondary-phase transformation is preferred at boundaries, either in the ferrite phase or at interphase interfaces after rolling, and even a few secondary precipitates can be found at the as-cast ferrite grain interiors as well. The influence of the secondary phase transformations on pitting resistance and hot ductility was investigated.

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Спивак, Л. В., В. С. Кирчанов et Н. Е. Щепина. « Полиморфные превращения в йодидном титане ». Физика твердого тела 64, n^o 11 (2022) : 1820. http://dx.doi.org/10.21883/ftt.2022.11.53341.400.

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Based on the analysis of differential scanning calorimetry data, the possibility of classifying the observed endothermic or exothermic transformations as phase transformations of the first oder is considered. Two approaches have been implemented. The first is based on the correspondence between the temperatures of the maximum conversion rate and the temperatures of the extrema on the second derivative of the differential scanning calorimetry signal with respect to temperature. In the second approach, the phase transformation is considered as a kind of kinetic reaction of a chemical process with the determination of some parameters included in the kinetic equations. In this case, the order parameter of such reaction n is obtained from the analysis of the differential scanning calorimetry signal shape in the region of phase transformation registration temperatures. Using the example of experiments carried out during thermal cycling of titanium iodide samples, it is shown that both the first and second approaches make it possible to fairly adequately attribute the processes that cause calorimetric effects on the dependences of differential scanning calorimetry to first-order phase transitions. In particular, the obtained results of differential scanning calorimetry during heating and cooling of iodide titanium show that polymorphic transformations in it are realized by various mechanisms depending on the rate of thermal cycling and the thermal history of the metal.

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Morrissey, K. J. « Interface structures in polycrystalline ceramic materials ». Proceedings, annual meeting, Electron Microscopy Society of America 44 (août 1986) : 468–71. http://dx.doi.org/10.1017/s0424820100143900.

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Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.

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Nigro, C. F., C. Bjerkén et Y. Mellbin. « Phase-field modelling : effect of an interface crack on precipitation kinetics in a multi-phase microstructure ». International Journal of Fracture 227, n^o 2 (17 janvier 2021) : 219–41. http://dx.doi.org/10.1007/s10704-020-00510-x.

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AbstractPremature failures in metals can arise from the local reduction of the fracture toughness when brittle phases precipitate. Precipitation can be enhanced at the grain and phase boundaries and be promoted by stress concentration causing a shift of the terminal solid solubility. This paper provides the description of a model to predict stress-induced precipitation along phase interfaces in one-phase and two-phase metals. A phase-field approach is employed to describe the microstructural evolution. The combination between the system expansion caused by phase transformation, the stress field and the energy of the phase boundary is included in the model as the driving force for precipitate growth. In this study, the stress induced by an opening interface crack is modelled through the use of linear elastic fracture mechanics and the phase boundary energy by a single parameter in the Landau potential. The results of the simulations for a hydrogenated ($$\alpha +\beta $$ α + β ) titanium alloy display the formation of a precipitate, which overall decelerates in time. Outside the phase boundary, the precipitate mainly grows by following the isostress contours. In the phase boundary, the hydride grows faster and is elongated. Between the phase boundary and its surrounding, the matrix/hydride interface is smoothened. The present approach allows capturing crack-induced precipitation at phase interfaces with numerical efficiency by solving one equation only. The present model can be applied to other multi-phase metals and precipitates through the use of their physical properties and can also contribute to the efficiency of multi-scale crack propagation schemes.

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John, P. K., A. C. Rastogi, B. Y. Tong, X. W. Wu et S. K. Wong. « Phase transformations at a nickel–silicon interface under transient annealing ». Canadian Journal of Physics 65, n^o 8 (1 août 1987) : 1037–43. http://dx.doi.org/10.1139/p87-170.

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We use intense incoherent light pulses of ~60 μs duration to induce reactions at a Ni–Si interface. Changes in morphology, composition, and electrical characteristics of the interfaces are studied. The diagnostics include scanning electron microscopy, Auger spectroscopy, X-ray analysis, and diffusion analysis. After annealing for a total of ~1 ms, the Si surface is found to support an intermixed and disordered Ni–Si layer consisting of mixed islands and flat structures. On further irradiation, after a certain threshold Ni density is reached in the Si, silicide growth takes place at the interface through an amorphous-to-crystalline transformation of this intermixed layer. The first phase to nucleate is mononickel silicide with a (200) orientation. This is attributed to kinetic effects, which optimize the heat of formation in the presence of excess Si.

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Lei, Ruo Shan, Shi Qing Xu, Ming Pu Wang, Ye Jun Li et Wei Hong Qi. « Size and Interface Coherency Dependent Phase Transformation of Niobium Nanoparticles Embedded in Copper Matrix by Mechanical Alloying ». Advanced Materials Research 602-604 (décembre 2012) : 243–48. http://dx.doi.org/10.4028/www.scientific.net/amr.602-604.243.

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The object of this work is to investigate the interface and size effects on the structural phase transition of Nb nanoparticles (NPs) embedded in Cu matrix. By means of X-ray diffraction analysis and high-resolution transmission electron microscopy observation, it is found that higher coherency of the Cu/Nb interface benefits the occurrence of phase transition in Nb NPs with larger sizes. The sufficient conditions for the transition are: (1) the size of Nb NPs should be smaller than 8 nm; (2) the Cu/Nb interfaces should be semi-coherent or coherent. The experimental results are consistent with the predictions of Bond Energy model.

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Sun, Jianguo. « 3-D crosswell transmissions : Paraxial ray solutions and reciprocity paradox ». GEOPHYSICS 60, n^o 3 (mai 1995) : 810–20. http://dx.doi.org/10.1190/1.1443819.

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Transmission of seismic waves through a 3-D earth model is of fundamental importance in seismology. If the model consists of many layers separated by curved interfaces, the only feasible solution to the transmitted waves is the one given by the geometrical optics approximation. Transmitted rays, transmitted wavefield, and the first Fresnel zone associated with a transmission point can be expressed by four 2 × 2 constant matrices constituting the 4 × 4 linearized ray transformation matrix. Generally, the ray transformation matrix can be constructed by dynamic ray tracing. However, if the layers are homogeneous, it can be formulated in closed form by using elementary vector calculus and coordinate transformations. Using the symplecticity of the ray transformation matrix, transmissions in opposite directions can be formulated by the ray transformation matrix for only one direction, and a reciprocity relation can be established. After the decomposition theorem for the ray transformation matrix, the transmitted wavefield in a model with many curved interfaces can be computed in a cascaded way. Using the [Formula: see text]‐matrix decomposition theorem, the normalized geometrical spreading factor can be expressed by means of the area of the first Fresnel zone of a transmission point. If seismic waves propagate through a locally spherical interface, the reciprocity relation may not hold. Using ray theory, this fact is shown by formulating the transmitted wavefield with the two principal radii of curvature of the transmitted wavefront at the transmission point under consideration. Using wave theory, this fact is shown by analyzing the Debye integral with the method of stationary phase.

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Gao, F., R. Devanathan, Y. Zhang, M. Posselt et W. J. Weber. « Atomic-level simulation of epitaxial recrystallization and phase transformation in SiC ». Journal of Materials Research 21, n^o 6 (1 juin 2006) : 1420–26. http://dx.doi.org/10.1557/jmr.2006.0176.

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A nano-sized amorphous layer embedded in an atomic simulation cell was used to study the amorphous-to-crystalline (a-c) transition and subsequent phase transformation by molecular-dynamics computer simulations in 3C–SiC. The recovery of bond defects at the interfaces is an important process driving the initial epitaxial recrystallization of the amorphous layer, which is hindered by the nucleation of a polycrystalline 2H–SiC phase. The kink sites and triple junctions formed at the interfaces between 2H– and 3C–SiC provide low-energy paths for 2H–SiC atoms to transform to 3C–SiC atoms. The spectrum of activation energies associated with these processes ranges from below 0.8 eV to about 1.9 eV.

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Asada, Takashi, Hiroyuki Kato et Kazuaki Sasaki. « 507 Phase-field model of transformation interfaces in stress-induced martensite ». Proceedings of Conference of Hokkaido Branch 2010.49 (2010) : 123–24. http://dx.doi.org/10.1299/jsmehokkaido.2010.49.123.

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Perkins, Jeff, M. H. Wu et K. Adachi. « Interfaces and substructures in copper-based shape memory alloys ». Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988) : 786–87. http://dx.doi.org/10.1017/s0424820100105990.

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The delineation of interfaces and substructures by conventional transmission electron microscopy is reviewed for three different transformations of interest in copper-based shape memory alloys.The first case considers the interfacial structure of martensite plate boundaries in a Cu-14.6Zn-16.1Al (atomic %) alloy. The detailed structure of such interfaces is important to their relative mobility in shape memory alloys. One-dimensional lattice images such as seen in Fig. 1 help to model the effect of substructural features in the martensite on the atomistic structure and so the mobility of such boundaries1. In the example shown, the presence of very thin structural faults with a 2H structure are detected within an otherwise 18R martensite plate.The second case describes the interaction of the state of parent phase order with the structure of bainite plates formed upon isothermal aging at 150-350 C in a Cu-27Zn-4Al (weight %) alloy . Two types of atomic ordering occur in the parent phase and tend to be inherited by the bainite transformation product.

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Lei, Yimin, Jie Sun, Hongwei Liu, Xuan Cheng, Fuyi Chen et Zongwen Liu. « Predictable and controllable dual-phase interfaces in TiO2(B)/anatase nanofibers ». Nanoscale 6, n^o 23 (2014) : 14237–43. http://dx.doi.org/10.1039/c4nr04613g.

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The TiO₂(B)/anatase interfaces were predicted successfully with a method with high practicality. The related phase transformation mechanism was also interpreted based on the predicted results.

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Goetz, Morgan, Moukrane Dehmas, Benoît Appolaire, Elisabeth Aeby-Gautier, Sandra Andrieu et Thomas Billot. « Decomposition of the β phase at intermediate temperature in β-metastable Ti-5553 alloy ». MATEC Web of Conferences 321 (2020) : 12024. http://dx.doi.org/10.1051/matecconf/202032112024.

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The present contribution focuses on the nature of the β → α transformation in Ti-5333 alloy at intermediate temperatures. It is indeed still unclear whether this transformation is only controlled by bulk diffusion or whether interfacial kinetics may play a role. To address this issue, we have combined SEM and STEM-EDX to measure the concentrations of Al, Cr, Mo, V and Fe in α intragranular precipitates as well as in the abutting β matrix, paying a particular attention to the concentrations at flat interfaces corresponding to the precipitates habit planes. The comparison with Calphad calculations suggests that interfaces are not at equilibrium during the thickening of the plates.

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Kraus, S. « HREM Studies of Interfaces in Zr02/Al203 Ceramics ». Proceedings, annual meeting, Electron Microscopy Society of America 43 (août 1985) : 218–19. http://dx.doi.org/10.1017/s0424820100118011.

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Because of its unusual mechanical and electrolytic properties, zirconia (Zr02) finds a wide variety of uses, such as refractories, oxygen sensors, heaters and extrusion dies. Zr02 exists in three polymorphic forms; the high temperature phase is cubic and is isostructural with CaF2 (fluorite); below 2350°C (in pure ZrO2 ), a tetragonally-distorted version of the fluorite structure exists. At still lower temperature, the tetragonal form (t-Zr02) transforms martensitically to a monoclinic structure (m-Zr02). This t→m transformation gives rise to the phenomenon of transformation toughening in ZrO2 -containing-ceramics, and thus provides ceramics with potential for high

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Gu, Su Yi, et Ji Hua Zhang. « Antiferromagnetic Transition and Martensite Transformation in γ-Mn-Fe Alloys ». Advanced Materials Research 146-147 (octobre 2010) : 916–19. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.916.

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The detailed investigation of internal friction and relative dynamic modulus has been carried out for the γ-MnFe alloys with 61.4at%~86.4at%Mn in the temperature range from -50 to 250 using LMR by means of force vibration method. The internal friction was found to exhibit in turn three peaks from higher temperature to the lower temperature on the internal friction-temperature curves. They are PA,PM and PT progressively. It can be concluded that PA may be connected with the stress-induced motion of magnetic domain. The PM was suggested to be originated from the stress-induced movement of interfaces between the fcc and fct phases. The PT is due to a relaxation process associated with the movement of the {101}-twin boundaries in the fct phase or fcc antiferromagnetic phase.

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Liu, Guo-Liang, Mei-Li Ding, Kun Zhang, Dan-Dan Qu, Yang Meng, Geng-Xing Luo et Shan-Wu Yang. « Microstructural and Interfacial Characterization of Ti–V Diffusion Bonding Zones ». Metals 12, n^o 12 (26 novembre 2022) : 2032. http://dx.doi.org/10.3390/met12122032.

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Ti and V were bonded together and subjected to high-temperature treatment at 1000 or 1100 °C for 16 h to study the microstructural evolution and interfacial behavior of Ti–V diffusion interfaces. The samples were prepared by electro-polishing and analyzed using scanning electron microscopy, electron probe microanalysis, electron back-scattered diffraction, and nano-indentation. The results indicated that Ti–V diffusion bonding interfaces comprises a martensite Ti zone, a body-center-cubic Ti (β-Ti) zone, and a V-based alloy zone. They are divided by two composition interfaces with V contents of ~13.5% and ~46%. The original interface between the pure Ti and the V alloy substrate falls within the β-Ti zone. The observation of acicular-martensite rather than lath-martensite is due to the distortion caused by the β-to-α phase transformation in the adjacent pure Ti. The recrystallization of β-Ti is distributed along the interface direction. The hardness varies across the Ti–V interface bonding zones with the maximum value of 7.9 GPa.

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Galenko, P. K., I. G. Nizovtseva, K. Reuther et M. Rettenmayr. « Kinetic transition in the order–disorder transformation at a solid/liquid interface ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 376, n^o 2113 (8 janvier 2018) : 20170207. http://dx.doi.org/10.1098/rsta.2017.0207.

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Phase-field analysis for the kinetic transition in an ordered crystal structure growing from an undercooled liquid is carried out. The results are interpreted on the basis of analytical and numerical solutions of equations describing the dynamics of the phase field, the long-range order parameter as well as the atomic diffusion within the crystal/liquid interface and in the bulk crystal. As an example, the growth of a binary A 50 B 50 crystal is described, and critical undercoolings at characteristic changes of growth velocity and the long-range order parameter are defined. For rapidly growing crystals, analogies and qualitative differences are found in comparison with known non-equilibrium effects, particularly solute trapping and disorder trapping. The results and model predictions are compared qualitatively with results of the theory of kinetic phase transitions (Chernov 1968 Sov. Phys. JETP 26 , 1182–1190) and with experimental data obtained for rapid dendritic solidification of congruently melting alloy with order–disorder transition (Hartmann et al. 2009 Europhys. Lett. 87 , 40007 ( doi:10.1209/0295-5075/87/40007 )). This article is part of the theme issue ‘From atomistic interfaces to dendritic patterns’.

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Carter, C. Barry, et Lisa A. Tietz. « Interfaces in high-Tc superconducting oxides ». Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 août 1989) : 178–79. http://dx.doi.org/10.1017/s0424820100152860.

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Interfaces in high-Tc superconducting oxides are influential during both the processing of bulk materials and the growth of thin epitactically aligned layers. In the first case, the formation of the superconducting phase involves the movement of phase boundaries during the solid-state reaction, while in the second, the phase boundary is formed as the superconducting material grows on the single-crystal substrate. Having formed the superconducting material, the superconducting phase will, in general, contain a large number of grain boundaries varying from the simple twin boundaries which can be produced during the cubic-to-tetragonal transformation, to low-angle grain boundaries, special high-angle grain boundaries, other high-angle grain boundaries and phase boundaries due to incomplete or on-going solid-state reactions. During the course of this presentation, recent results on these topics will be reviewed, paying particular attention to the more widely studied material, YBa2Cu3O6+x.The importance of grain boundaries in high-Tc superconducting oxides has been firmly established by the systematic analysis of Dimos et al who have shown that the misorientation of the grains in layers of YBa2Cu3O6+x which had been grown on polycrystalline SrTiO3 substrate varies with the relative misorientation between the grains.

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Шеляков, А. В., Н. Н. Ситников, И. А. Хабибуллина, Р. В. Сундеев et О. Н. Севрюков. « Особенности кристаллизации аморфных сплавов TiNiCu с высоким содержанием меди ». Физика твердого тела 62, n^o 6 (2020) : 829. http://dx.doi.org/10.21883/ftt.2020.06.49332.31m.

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Alloys of the quasi-binary TiNi – TiCu system with a copper content of 25, 30, 35, and 40 at. % were obtained by planar flow casting technique at a cooling rate of 10^6 K/s in the form of ribbons 30–50 μm thick and 10–20 mm wide. The structure and phase transformations in the alloys were studied using electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry. It was found that in the initial state, the alloys with 25 and 30 at.% Cu have an amorphous-crystalline structure, undergoing a one-stage polymorphic crystallization of the amorphous state on heating in a calorimeter with the formation of austenite B2 phase, which on cooling to room temperature proceeds to orthorhombic B19 phase due to the martensitic transformation. It is shown that the alloys with 35 and 40 at.% Cu at quenching become amorphous, and upon heating, two-stage crystallization occurs (primary and eutectic) with the formation of a two-phase structure - the tetragonal B11 (TiCu) phase with a small fraction of B2 phase. Moreover, an increase in the copper content leads to a decrease in the onset temperature of crystallization.

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Мусабиров, И. И., И. М. Сафаров, Р. М. Галеев, Р. А. Гайсин, В. В. Коледов et Р. Р. Мулюков. « Анизотропия термического расширения поликристаллического сплава системы Ni-Mn-Ga, подвергнутого пластической деформации ковкой ». Физика твердого тела 60, n^o 6 (2018) : 1051. http://dx.doi.org/10.21883/ftt.2018.06.45975.28m.

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AbstractThe formation of a sharp crystallographic texture in a Ni–Mn–Ga Heusler alloy by the multiple isothermal forging has been studied. An analysis of the thermal expansion near the martensitic transformation temperatures in the as-cast and forged states of the alloy shows that the thermomechanical treatment leads to an increase in the anisotropy of the sample geometric size changing during the phase transformation, which favors an increase in the functional characteristics of the alloy. The structural studies show that the alloy structure after multiple isothermal forging has the bimodal distribution of grain sizes. The formation of the bimodal structure by forging is assumed to make it possible to enhance the stability of the functional properties of the alloy during repeated cycles of the phase transformation.

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Lee, Dong Nyung, et Heung Nam Han. « Directed Growth of Ferrite in Austenite and Kurdjumov-Sachs Orientation Relationship ». Materials Science Forum 715-716 (avril 2012) : 128–33. http://dx.doi.org/10.4028/www.scientific.net/msf.715-716.128.

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The solid phase transformation of a metastable phase into a stable phase needs the activation energy. The energy is usually supplied in the form of thermal energy. When the nucleation takes place, the strain energy may develop in the metastable matrix and the stable nucleus. The strain energy can result from differences in density of the nucleus and matrix and the lattice mismatch between the nucleus and matrix. The stable-metastable interface region has the highest strain-energy density in the maximum Youngs modulus direction of the stable phase. Accordingly, the growth rate of the stable phase is the highest in its highest Youngs modulus directions. As the transformation temperature decreases, the strain energy contribution increases and the growth rate anisotropy is likely to increase. When austenite transforms into ferrite at low temperatures, the directed growth of ferrite is observed as forms of Widmanstätten ferrite plates and acicular ferrite plates. The maximum growth direction of ferrite is along the maximum Youngs modulus direction of ferrite, <111>α, and the broad interfaces are parallel to the maximum growth direction and formed so that they minimizes the shear strain energy in the interface layer. The directed growth results in the Kurdjumov-Sachs orientation relationship between austenite and ferrite, <111>α//<110>γand {110}α//{111}γ.

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Wei, Zhao Zhao, Xiao Ma et Xin Ping Zhang. « Defect Structure and Martensitic Transformation Crystallography in Ni₂MnGa Alloy ». Materials Science Forum 687 (juin 2011) : 463–66. http://dx.doi.org/10.4028/www.scientific.net/msf.687.463.

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Ferromagnetic shape memory alloys can produce large strains in a magnetic field by twin boundary motion. The mobility of parent-martensite inter-phase interfaces and twin-twin inter-variant boundaries is closely related to their interfacial structures and the mechanism of migration, therefore a thorough understanding of its nature is of importance. A physical model of the structure of parent-martensite interface has been developed recently based on dislocation theories and topological arguments. On the basis of the topological model, the present work performs a theoretical study of the defect structure of the martensitic interface, and the transformation crystallography in Ni2MnGa alloy. The habit plane, i.e., the parent-martensite interface plane was determined to be (-0.761, -0.054, -0.646)Pfor the parent crystal index frame, and (-0.818, 0.067, -0.571)Mfor the martensite frame. The habit plane inclination angle is 5.945° and 5.953° with respect to the terrace plane in the parent and martensite crystals, respectively.

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Синицын, В. В., О. Г. Рыбченко, В. Б. Ефимов et А. А. Вирюс. « Аморфный лед средней плотности, полученный разложением водно-гелиевого геля ». Физика твердого тела 65, n^o 8 (2023) : 1307. http://dx.doi.org/10.21883/ftt.2023.08.56147.103.

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The article presents experimental studies of structural changes that occur during heating of nanosized powders of amorphous ice obtained by decay of a water-helium gel. Thermal annealing of the obtained samples was carried out by short exposures (about 15 minutes) at different temperatures in the range of 110-230K. The behavior of the amorphous phase during annealing was analyzed within the framework of its description by a mixture of amorphous ices of low and medium density (LDA and MDA, respectively). It was found that at the such description, the virgin sample was predominantly in the MDA state, while the proportion of the LDA phase was about 7 times less (MDA/LDA ≈ 7:1). It has been established that during annealing, a multistage process of structural transformations of the initial LDA + MDA sample takes place: from initial changes in the amorphous state at 110 K through crystallization of the cubic ice phase Ic with its intensive growth at a temperature of 130 K to the transformation of cubic ice into the hexagonal phase Ih in the temperature range T =135÷230K.

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Gong, C. L., F. S. Han, Z. Li et M. P. Wang. « Internal friction related to viscous motion of phase interfaces during thermoelastic martensitic transformation ». Philosophical Magazine 87, n^o 16 (juin 2007) : 2281–97. http://dx.doi.org/10.1080/14786430601156193.

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Zhang, Hairui, Cong Wang, Junqing Guo, Wuhui Li, Chu Cheng, Nan Xiang, Tao Huang, Hongzhi Niu, Deliang Zhang et Fuxiao Chen. « Phase Transformation, Microstructural Evolution and Tensile Properties of a TiH2-Based Powder Metallurgy Pure Titanium ». Metals 14, n^o 11 (25 octobre 2024) : 1218. http://dx.doi.org/10.3390/met14111218.

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Multiple phase transformations were carried out during dehydrogenation process of TiH2-based powder metallurgy. The influence of phase transformation on the microstructure is highly worthy of attention. In situ synchrotron radiation was employed to investigate the phase transformation sequence of TiH2 powder compact during the vacuum sintering process. It was found that a transformation route TiH1.971 → TiH2 + TiH + TiH0.71 + α(H) → TiH + TiH0.71 + α(H) → TiH + TiH0.71 + α(H) + β(H) → α(H) → α took place, resulting in an equiaxed microstructure. Increasing heating rate and avoiding the intense dehydrogenation to retain hydrogen-rich β (β(H)) and TiHx aciculae at the interfaces is found to be a feasible method to fabricate hierarchical α-Ti structures. A fully dense fine martensitic microstructure was produced after fast heating the TiH2 powder compact to 1100 °C and an immediate hot extrusion. Subsequently, by vacuum annealing treatment at 700 °C, composite α/βt lamellar structures were generated and a simultaneously enhanced tensile strength of 746 MPa and excellent elongation to fracture of 33.8% were achieved. It is suggested that adjusting the dehydrogenation reactions of TiH2-based powder metallurgy is conductive to generating hierarchical lamellar structures with a highly promising combination of strength and ductility for pure Ti.

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Feng, Lulu, Kaiming Wu, Feng Zhou et WeiWen Qiao. « Effect of Al on Pearlite Transformation and Spheroidization of High Carbon Steel ». Science of Advanced Materials 13, n^o 6 (1 juin 2021) : 1088–95. http://dx.doi.org/10.1166/sam.2021.4022.

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Normalizing and isothermal spheroidizing annealing tests were carried out on two types of high-carbon steel specimens with different aluminum (Al) contents. The effects of Al content on the phase transformation and spheroidization of high-carbon steel were analyzed. It was found that addition of Al element can increase the pearlitic eutectoid transition temperature of high-carbon steel, making the eutectoid point move toward the high-carbon direction, and inhibiting the precipitation of proeutectoid cementite during pearlitic transformation. The higher the Al content, the greater the undercooling degree during pearlitic transformation and the finer the pearlite lamellar spacing would be after transformation. In addition, the finer pearlite lamellar spacing allowed the test steel to achieve more phase interfaces in the same crystal range and more dislocations and other defects on the interface, thus providing more nucleation centers for lamellar cementite during isothermal spheroidizing annealing. In addition, more defects provided more diffusion channels for carbon during spheroidizing annealing and smaller interlamellar spacing to shortening the diffusion distance of carbon atoms, thus accelerating carbon diffusion rate and spheroidizing the lamellar cementite into granular one. The addition Al element can improve the machinability of steel and facilitate the commercial application of pearlitic steel.

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Yanar, C., J. M. K. Wiezorek, V. Radmilovic et W. A. Soffa. « Characterization of Interphase Interfaces Developed During the Ordering Transformation (ε (A3) →τ (L10)) In Manganese-Aluminum Alloys ». Microscopy and Microanalysis 6, S2 (août 2000) : 364–65. http://dx.doi.org/10.1017/s1431927600034310.

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Alloys based on the ferromagnetic τ-phase, which may be established in the Mn-Al system for near equiatomic composition [1], exhibit high magnetocrystalline anisotropy and coercivity and are of interest for advanced permanent magnet applications [2], Their technologically important properties depend strongly on the microstructure and defect structure development associated with the transformation from the disordered hexagonal (A3) ε-phase to the ordered tetragonal (L10) τ-phase. The structure, morphology and chemistry of the (ε/τ) interphase interfaces have been studied by methods of optical and electron microscopy (OM, SEM and TEM) in order to determine the nature of this technically important and scientifically interesting phase transformation. The optimization of processing-property relationships for this class of ferromagnetic materials requires a detailed understanding of the mechanisms facilitating the ordering process.The τ-phase nucleates at prior ε-grain boundaries (ε-GB) and exhibits a serrated, faceted growth morphology (FIG. l).

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Chen, Qing, Anders Engström, Lars Höglund, Henrik Strandlund et Bo Sundman. « Thermo-Calc Program Interface and Their Applications - Direct Insertion of Thermodynamic and Kinetic Data into Modelling of Materials Processing, Structure and Property ». Materials Science Forum 475-479 (janvier 2005) : 3145–48. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.3145.

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Thermodynamic and kinetic data are generally essential for quantitative modeling of materials processing, structure, and property. Thermo-Calc program interfaces, including TQ, TCAPI, and TC MATLAB Toolbox, provides a hierarchy of APIs for application programmers to access thermodynamic and kinetic data via the kernel of Thermo-Calc and DICTRA, the most widely used software and database system for multi-component phase equilibrium and phase transformation calculations. With these program interfaces, variation of thermodynamic and kinetic properties can be directly obtained in real time as the local temperature, pressure, or composition changes. The structure and usage of the Thermo-Calc program interfaces will be introduced in this article. Successful application examples will be illustrated.

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Santofimia, M. J., John G. Speer, Lie Zhao et Jilt Sietsma. « Model for the Annealing of Partial Martensite-Austenite Microstructures in Steels ». Solid State Phenomena 172-174 (juin 2011) : 567–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.567.

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The microstructure formed in a steel after a partial martensitic transformation contains martensite-austenite assemblies with similar chemical composition in the two phases. In the absence of carbide precipitation, further annealing or tempering of this microstructure is believed to promote carbon partitioning from the martensite to the austenite. Experimental observations suggest that this carbon diffusion might take place in combination with migration of martensite-austenite interfaces. In this work, the effect of the martensite and austenite dimensions on the interaction between the carbon partitioning from martensite to austenite and the interface migration during annealing of martensite-austenite microstructures is analyzed. With that aim, simulations have been done by using a model in which the chemical potentials of carbon in martensite and austenite are assumed to be the same at the interface and motion of the phase interface is occurring when an appropriate driving force is present. Carbide precipitation is precluded in the model, and three different assumptions about interface mobility are considered, ranging from a completely immobile interface to the relatively high mobility of an incoherent ferrite–austenite interface.

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Римский, Г. С., К. И. Янушкевич, Н. М. Белозорева, Д. П. Козленко et А. В. Руткаускас. « Кристаллическая структура и магнитные характеристики твердых растворов Mn-=SUB=-1-x-=/SUB=-Fe-=SUB=-x-=/SUB=-NiGe ». Физика твердого тела 63, n^o 3 (2021) : 393. http://dx.doi.org/10.21883/ftt.2021.03.50593.208.

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Substitutional solid solutions Mn1-xFexNiGe (0.05≤x≤1.00) were synthesized. The crystal structure in the temperature range of 20 - 300 K has been studied by X-ray and neutron diffraction. At T = 200 K, a phase transformation from a hexagonal structure of the Ni2In type to an orthorhombic structure (S.G. Pnma) has been observed. The magnetic properties of these compounds were also investigated in the temperature range of 5 - 300 K and external magnetic fields up to 10 T. The temperature of the "magnetic order - magnetic disorder" phase transformation was found to decrease from 272 to 132 K with an increase in concentration x from 5 to 30 mol%.

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Polatidis, Efthymios, Nikolay Zotov et Eric J. Mittemeijer. « Stress-induced phase transformations in thermally cycled superelastic NiTi alloys : in situ X-ray diffraction studies ». Powder Diffraction 30, S1 (9 mars 2015) : S76—S82. http://dx.doi.org/10.1017/s0885715614001456.

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In situ laboratory-based and in situ synchrotron X-ray diffraction techniques were employed to study quantitatively the strain-induced austenite-to-martensite (A–M) transformation in thermally cycled (TC) superelastic NiTi alloys. The propagation of the A–M interfaces and the evolution of the microstructure were traced during uniaxial tensile loading. It was shown that the TC material exhibits localized transformation via the propagation of transformation bands. The amount of the martensite phase depends approximately linearly on the applied strain. Analysis of the broadening of the austenite diffraction lines indicates the presence of highly deformed austenite grains within the transformation bands. Analysis of the austenite diffraction-line shifts indicates that the overall lattice strain in the (retained) austenite in the transformation bands differs from that of the austenite in the adjacent untransformed regions.

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Johnson, Nathan S., Donald W. Brown, John S. Carpenter, Behnam Amin-Ahmadi, Craig A. Brice, Branden B. Kappes et Aaron P. Stebner. « The roles of kinematic constraint and diffusion in non-equilibrium solid state phase transformations of Ti-6Al-4V ». Applied Physics Letters 120, n^o 17 (25 avril 2022) : 171901. http://dx.doi.org/10.1063/5.0084229.

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A solid state phase transformation of Ti-6Al-4V was studied using high speed in situ x-ray diffraction measurements made during rapid cooling of a cold metal transfer arc weld bead deposited onto a water cooled substrate. Analysis of body centered cubic (BCC) and hexagonal close packed (HCP) lattices revealed an abrupt, nonlinear shift in the lattice parameters of both phases just after the HCP phase had nucleated. Postmortem transmission electron microscopy confirmed that V diffusion was mostly suppressed during cooling. Together, these results indicate that at this cooling rate of approximately 104 K/s, which is representative of cooling rates of many additive manufacturing and welding processes, kinematic coherency of the BCC–HCP interfaces gives rise to the anomalous lattice expansion and contraction behaviors of both phases during the initial nucleation and growth stages of (mostly) martensitic transformation from BCC to HCP; the role of diffusion in such lattice anomalies is shown to be minimal.

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Johnson, Nathan S., Donald W. Brown, John S. Carpenter, Behnam Amin-Ahmadi, Craig A. Brice, Branden B. Kappes et Aaron P. Stebner. « The roles of kinematic constraint and diffusion in non-equilibrium solid state phase transformations of Ti-6Al-4V ». Applied Physics Letters 120, n^o 17 (25 avril 2022) : 171901. http://dx.doi.org/10.1063/5.0084229.

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A solid state phase transformation of Ti-6Al-4V was studied using high speed in situ x-ray diffraction measurements made during rapid cooling of a cold metal transfer arc weld bead deposited onto a water cooled substrate. Analysis of body centered cubic (BCC) and hexagonal close packed (HCP) lattices revealed an abrupt, nonlinear shift in the lattice parameters of both phases just after the HCP phase had nucleated. Postmortem transmission electron microscopy confirmed that V diffusion was mostly suppressed during cooling. Together, these results indicate that at this cooling rate of approximately 104 K/s, which is representative of cooling rates of many additive manufacturing and welding processes, kinematic coherency of the BCC–HCP interfaces gives rise to the anomalous lattice expansion and contraction behaviors of both phases during the initial nucleation and growth stages of (mostly) martensitic transformation from BCC to HCP; the role of diffusion in such lattice anomalies is shown to be minimal.

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Zheng, Yu, et Peng Xu. « Effect of Nb Content on Phase Transformation and Comprehensive Properties of TiNb Alloy Coating ». Coatings 13, n^o 7 (1 juillet 2023) : 1186. http://dx.doi.org/10.3390/coatings13071186.

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As a β phase transformation promoting element of titanium alloy, the Nb element can induce different phase transformations of the alloy, improving the comprehensive properties of the alloy. However, the research on the effect of Nb content on the properties of TiNb alloy coating during laser cladding is not comprehensive. Herein, TixNb (x = 32.5~62.5 wt.%) alloy coatings were prepared by laser cladding technology, and their mechanical properties, corrosion resistance, and biocompatibility were analyzed. The results show that the Nb element promotes the precipitation of different phase components in the phase transformation-induced coating of titanium alloy. The grain refinement during the laser cladding process effectively improves the microhardness of the TiNb alloy coating. At the same time, the wear resistance of the α″ + β dual-phase Ti32.5Nb alloy is enhanced. In addition, with the increase in Nb content, the coating exhibits better corrosion resistance. In vitro cell experiments showed that the TiNb alloy coating had excellent biocompatibility compared to the TC4 substrate. Therefore, the laser-clad TiNb alloy coating has high comprehensive performance and has reference value in the field of biological implantation.

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Suvorova E. I., Solomkin F. Yu., Arkharova N. A., Sharenkova N. V. et Isachenko G. N. « Microstructure and phase composition of an alloy of iron and chrome disilicides ». Semiconductors 56, n^o 2 (2022) : 151. http://dx.doi.org/10.21883/sc.2022.02.53041.33.

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The phase composition, microstructure, and interphase interfaces of the disordered CrSi2-FeSi2 solid solution obtained by spontaneous crystallization (before and after annealing) have been investigated by scanning, transmission electron microscopy, electron diffraction, and X-ray energy dispersive spectrometry. The as-grown samples contained the phases of CrSi2 with the P6422 hexagonal structure and FeSi2 with the P4/mmm tetragonal structure. Annealing of the samples led to the phase transformation of tetragonal FeSi2 into the orthorhombic modification Cmca. Precipitates of cubic iron monosilicide FeSi with space group P213, nano-precipitates of Si and silicon silicide Cr5Si3 with a tetragonal structure I4/mcm were observed inside the FeSi2 grains. Impurities of interstitial Cr atoms with a concentration up to 2.0 at% are found in iron (di)silicides grains in all samples. The structure of the CrSi2 phase remains unchanged after annealing; the concentration of impurity iron atoms is about 0.7 at%. Orientation relationships between the crystal lattices of the phases are established and strains due to the mismatch of the crystal lattices are determined. Keywords: chromium disilicide, iron disilicide, interphase interfaces, transmission electron microscopy, energy dispersive X-ray spectrometry.

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Suvorova, Elena I., Natalya A. Arkharova, Anna G. Ivanova, Fedor Yu Solomkin et Philippe A. Buffat. « Phases and Interfaces in the Cr–Fe–Si Ternary System : X-ray Diffraction and Electron Microscopy Study ». Inorganics 11, n^o 2 (3 février 2023) : 73. http://dx.doi.org/10.3390/inorganics11020073.

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The ternary Cr-Fe-Si system was investigated with X-ray diffraction, energy dispersive X-ray spectrometry, scanning and transmission electron microscopy, and electron diffraction. Samples melted at 1723 K were examined right after cooling or after annealing at 1073 K for 3 days to determine phases, grain sizes, and interphase interfaces. During annealing, a polymorphic transformation of the tetragonal α-FeSi2 to the orthorhombic β-FeSi2 phase occurs, while CrSi2 retains its hexagonal structure at high-temperature treatment. Thin layers of ε-FeSi with a cubic structure were observed and identified within the CrSi2 grains. Crystallographic orientation relationships are determined at the interphase interfaces. The contributions of lattice mismatch and thermal expansion coefficient misfit to deformation are discussed.

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Егоров, В. М., П. Н. Якушев, М. А. Арсентьев et А. С. Смолянский. « Влияние гамма-облучения на фазовые переходы в политетрафторэтилене, допированном диоксидом кремния растительного происхождения ». Физика твердого тела 62, n^o 8 (2020) : 1339. http://dx.doi.org/10.21883/ftt.2020.08.49624.083.

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Abstract The effect of gamma irradiation and doping with silicon dioxide on the first-order solid-state phase transition in polytetrafluoroethylene is studied by the differential scanning calorimetry method. A quantitative analysis of the profiles of the heat capacity peaks is carried out on the basis of the theory of diffuse phase transitions. It is shown that the elementary volume of the phase transformation depends on the γ irradiation and the concentration of silicon dioxide.

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Long, Xiaoyan, Yu Zhang, Dongyun Sun, Dongxin Yin, Wei Liu, Zhen Zhang, Fucheng Zhang et Yanguo Li. « Study on the Influence of Pre-Formed Phase on Accelerating Bainitic Transformation ». Coatings 13, n^o 10 (27 septembre 2023) : 1700. http://dx.doi.org/10.3390/coatings13101700.

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Bainitic transformation goes through three stages: incubation period, nucleation, and growth. The long transformation time is not conducive to industrial production, which restricts its development. Therefore, research on accelerating bainitic transformation is based on the situation of energy saving and efficiency saving. The methods to accelerate bainitic transformation include the control of alloy elements, heat treatment control, etc. This paper focuses on the influence of the pre-formed phase on the kinetics of accelerated bainite transformation. Combined with existing research and experiments, it clarifies the influence of pre-formed ferrite, pre-formed martensite, and precipitated second-phase particles on the kinetics of bainitic transformation. Moreover, it clarifies the characteristics of bainitic transformation in terms of microstructure characterization.

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