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Development of the theory of rapid growth in terms of phase field model was provided for multi-grain case. The growth of polycrystalline multi-component alloying systems, which driving force regarded as the Gibbs free energy change on crystallization, was studied with the help of the model of fast phase transformations. The special attention was given to the specific rapid solidification features, affecting on the need of using both classical slow and fast variables. Finally, the evolution equations for diffusion flux and gradient flow were developed concerning multi-phase interpolation among growing poly-crystallites. In the limit of relaxation time of fast thermodynamic variables the model tends to restore the Moelan’s phase field model of anisotropic grain growth. [ABSTRACT FROM AUTHOR]

In the paper, the formation of the gradient structure of the sample from 321 stainless obtained by the electron-beam additive manufacturing method is researched. For obtaining a high-quality product by the method of additive manufacturing, it is necessary to define possible values of electron-beam 3D-printing parameters. The macrostructure images show the layers of printing, but it is difficult to differentiate the individual elements of the sample structure. Upon further investigation, differences in the microstructure in the direction of sample growth in the next layer were revealed. According to X-ray analysis, the final sample obtained by electron-beam 3D-printing is in two-phase state: α- and γ-Fe. The proportion of the α-Fe phase in the lower part of the sample is 4.2 % higher than in the upper part. This indicates a recrystallization growth of the grain structure of the material. [ABSTRACT FROM AUTHOR]

The fine-grained microstructures evolved during friction stir welding of aluminum alloys often exhibit abnormal grain growth during post-weld heat treatment. To avoid this undesirable phenomenon, a pre-strain rolling approach has been employed in the present study. The proposed method was based on the idea that the pre-strain rolling would promote recrystallization instead of the abnormal grain growth during the subsequent heat treatment. To validate this concept, the produced welds were cold rolled in two different directions—either parallel or perpendicular to the weld path—prior to the standard T6 tempering. In both cases, the pre-strain rolling was found to be effective for suppression of the abnormal grain growth. Moreover, the revealed effect was sensitive to the rolling path. Specifically, the pre-rolling along the weld line resulted in the finest final grain size in treated-treated welds. This observation was explained in the terms of relatively high Taylor factor, which enhanced recrystallization behavior during subsequent annealing. [ABSTRACT FROM AUTHOR]

The regularities of additively manufactured titanium alloy deformation behavior are investigated. It is revealed that at deformation along the direction of columnar grains growth the samples are characterized by high relative elongation and viscous dimple structure of fracture surface. At deformation across the grain growth direction, deformation and fracture occur in the same way, but the grain boundaries make an additional contribution to the failure of samples. Influence of pores on the deformation behavior and fracture formation features is not observed. [ABSTRACT FROM AUTHOR]

The Monte Carlo simulation method is now widely applied to materials science and engineering to the study of the kinetics of grain growth in two dimensions. This review Survey includes the grain growth kinetics, Grain Size and Grain Distribution by Monte Carlo simulation method. The initial distribution of orientations is chosen at random and the system evolves so as to reduce the number of nearest neighbor pairs of unlike crystallographic orientation. The temporal evolution of the microstructure is monitored to yield the time dependence of the size and shapes of the grains. A procedure incorporating the Metropolis algorithm which helps in developing the code for computer simulation is given as examples, two codes written using MATLAB software to simulate microstructure evolution using 2D ISING and POTTS Q-States Model would be demonstrated. [ABSTRACT FROM AUTHOR]

Microstructural predictions on multi-pass processes are very challenging because the grains topology evolves in a very wide range, due to the coupled action of hardening, recovery, grain growth (GG), discontinuous dynamic and post dynamic recrys-tallization (DRX and PDRX). Classical models reach their limits. More physical approaches taking into account the complexity of the topology becomes necessary. In this article, DIGIMUQ®, the first commercial full field (FF) simulation software dedicated to grain growth and recrystallization modeling will be presented. Its ability to model industrial processes will be illustrated on an industrial-like 2D plate rolling process. [ABSTRACT FROM AUTHOR]

Effect of thermal deformation regimes on the austenite grain growth is studied in the article. The austenite grain growth curve based on the experimental data is constructed. Conclusion about temperature, deformation degree and rate effect is made. [ABSTRACT FROM AUTHOR]

A novel CaO-based sorbent was found to show excellent performance as an energy storage material for a thermochemical energy storage system. The sorbent was synthesised using the Pechini method and doped with hydroxyapatite and calcium aluminate. It retained a carbonation conversion capacity of 84% over 40 calcination and carbonation cycles. The improved performance is ascribed to the prevention of grain growth and sintering by the dopants. The use of a proportion of hydroxyapatite in place of calcium aluminate in doped CaO-based sorbents could save costs due to the low price of hydroxyapatite precursors. [ABSTRACT FROM AUTHOR]

The x(NdFeO3) - 1-x(PbTiO3) where x = 0.2 solid solution was prepared using solid state reaction route. The X-ray diffraction (XRD) data reveals the single phase formation. The microstructure shows grain growth with lesser porosity. The energy dispersive analysis confirms the presence of elements in stochiometric proportion. The polarization vs. Electric field loop estabilished a ferroelectric type behavior but lossy in nature. This lossy nature may be due to the presence of large leakage current in solid solution. The Magnetization vs. Magnetic field plot exhibits a unsaturated hysteriss loop indicates that the sample is not purely ferromagnetic. [ABSTRACT FROM AUTHOR]

Synthesis of Co1-xTixFe2O4 solid solutions for 0.1≤x≤0.4 using the solid-state-reaction rate has been done. The prepared samples were characterized by using XRD (X-ray diffraction) and SEM (Scanning Electron Microscopy). Magnetic studies have been done using Vibrating Sample Magnetometer (VSM). XRD confirmed that Cobalt Ferrite spinel cubic structure in all prepared samples. The lattice parameter ‘a’ increases with increase in the concentration of Ti. SEM micrograph shows good grain growth in all samples. Magnetic Study reveals that the M-H curves of all the prepared samples taken at room temperature are very well saturated. The maximum value of remnant magnetization (Mr ∼13.9 emu/g) and saturation magnetization (Ms ∼74.4 emu/g) has been observed for x =0.2 sample. Coercivity does not show any regular variation with increase in the molar concentration of Ti in CoFe2O4 at A-site. [ABSTRACT FROM AUTHOR]

The pure and V-Nd co-doped TiO2 samples are prepared by the modified sol-gel process. The phase formation is confirmed by XRD spectrum. Phase transformation is delayed in V-Nd co-doped TiO2 (TVN) samples compared to pure TiO2. The particle size is comparatively small in TVN samples at both the temperature 450 °C and 900 °C. Hence the effect of Nd doping is dominated over V doping in both phase transformation and grain growth process of TiO2. [ABSTRACT FROM AUTHOR]

A methodology is proposed to obtain the grain growth coefficients operating during solidification of a near eutectic Al-Ni alloy from data on solid fraction evolution, latent heat of solidification and., volume grain density. These parameters are obtained using Newton Thermal Analysis (NTA), metallographic methods and the Free Growth Method (FG). In order to validate the methodology a heat transfer-solidification kinetics model was implemented. Results suggest that this methodology could be applied to obtain useful information needed to simulate grain growth during eutectic solidification. [ABSTRACT FROM AUTHOR]