Papers by Keyword: Phase Field Model

Abstract: This study leverages artificial intelligence (AI) to advance materials science, focusing on microstructural evolution in binary alloys during spinodal decomposition. Following the formulation of Zhu et al., we explore the microstructure evolution during interface-controlled spinodal decomposition. A comprehensive dataset captures the dynamic microstructural changes, highlighting the model's efficiency in analyzing complex data. The innovative use of an Autoencoder- ConvLSTM model enables precise, low-error microstructural transformation predictions, demonstrating AI’s potential in materials science research. This work provides a deeper understanding of material behaviors and offers new research directions.

Abstract: As an increasingly mature additive manufacturing technology for metal materials, Selective Laser Melting (SLM) technology has become a hot topic in many application fields. However, due to the fast-moving velocity and small scale of the laser beam in the SLM process, it is very difficult to directly observe the microstructural changes in the SLM additive manufacturing process. In this study, a macro-micro coupled simulation model of Inconel 718 SLM process was established to study the solidification behavior of the molten pool. The macro temperature field is obtained by the finite difference method based on the birth and death grid algorithm. The local temperature intercepted from the macro temperature field is employed as the input condition for phase field microstructure calculation. Dendrite morphology, intercellular spacing, and microsegregation are simulated under the coupled model. The result shows that the solidification structure of IN718 alloy in the micro molten pool formed by SLM grows in the form of a non-flat interface. The primary dendrite spacing predicted by the simulation is in good agreement with Hunt model at the initial stage of solidification. The solute trapping caused by non-equilibrium solidification makes dendrites dissolve more Nb, resulting in microsegregation.

Abstract: In this work, the utilization of a phase-field ductile fracture model in the failure analysis of advanced steels is investigated. The importance of advanced steels is potentially proven, for instance in automotive industry, due to its light weight, which entails the crucial role of fracture analysis in these structures. A third generation advanced high strength USS CR980XG3™️ AHSS material is considered to perform fracture analyses. For this purpose, the necessary data regarding the stress distribution and fracture patterns from digital image correlation tests are utilized for subsequent numerical experimentations.A recent phase-field model of ductile fracture is employed herein for the analysis of crack advance in this class of materials. The significance of the choice of material properties using this model is shown through the analysis of an experimental fracture benchmark called Shear Fracture specimen, through assessment of crack evolution and force diagrams.

Abstract: Effects of the electric inclusion in ferroelectrics on the stress and electric field concentration and polarization switching are investigated based on a phase field approach containing the time-dependent Ginzburg-Landau equation. To capture a clear physical picture with the simulation, the crack medium in the electric inclusion is taken into account explicitly as a crack fluid medium as water, oil or air in region. The simulations exhibit a macroscopic electric field concentration in the electric inclusion filled with air, and a significant influence on the domain evolution from the micro perspective, while the electric inclusion filled with water have little influence. The numerical calculations indicated that, when the dielectric constant inside the flaw are much smaller than the dielectric constant of the ferroelectric matrix, the electric field inside the crack medium are enhanced much higher than the applied electric loading. The result implies the domain evolution takes place with the minimization of total free energy, which involves the high electric field energy derived from the electric inclusion. Therefore, the crack fluid medium in ferroelectric plays in importation role in the effect on the non-uniform distribution of the stress and electric field.

Abstract: Heteroepitaxially grown multilayered thin film structures have been attracted of great interest due to its potential applications in photovoltaic/light emitting/electronics devices. The thin film morphology plays an important role in enhancing its related physical properties. It is not easy to simulate the multi-layered thin film structures due to the influence of the interface/surface fluctuation. However, the phase field method, based on thermodynamics and Cahn-Hilliard diffusion model, can predict the thin film morphologies without tracking the interfaces. In this paper, a new phase field model was developed for predicting multi-layer structures with multi-order parameters. The morphologies with strain distributions of the quantum wells, quantum dots and buffer layers structures were investigated in the current study. We found that the strain distribution has a strong effect on the suface/interface morphologies in the multilayered structures. Some simulation results are consistent with experimental observations.

Abstract: The phase field models have been built to study the influence of the nonuniform grain boundary energy for abnormal growth of grains in the AZ31 magnesium alloy in the real time and space. The simulated results show that if the grains of a certain orientation with low grain boundary energy in the AZ31 Mg alloy, abnormal grain growth will occur after annealing treatment, and only if the local low grain boundary energy is less than 0.98σ_0, can the certain grains grow abnormally in the microstructure.

Abstract: Environmentally-assisted material degradation involves mass transport and mechanical processes interacting in the material. A well-known example is hydrogen-induced stress-corrosion cracking. One major challenge within this scope is the quantification of the coupling mechanisms in question. The computational modeling of environmentally-assisted cracks is the key objective ofthis investigation and realised within the theory of gradient-extended dissipative continua with length-scales. The modeling of sharp crack discontinuities is replaced by a diffusive crack model based onthe introduction of a crack phase-field to maintain the evolution of complex crack topologies. Withina thermodynamical framework allowing for mechanical and mass transport processes the crack phase-field is capable to model crack initiation and propagation bythe finite element method. As complexcrack situations such as crack initiation, curvilinear crack patterns and crack branching are usuallyhard to realise with sharp crack models, they can be assessedwithout the requirement of a predefinedcrack path within this method. The numerical modeling of a showcase demonstrates a crack initiationas well as a crack propagation situation with respect to the determination of stress-intensity factors; acrack deviation situation with a curvilinear crack path is modeled by the introduction of a geometricalperturbation and a locally enhanced species concentration

Abstract: Since the growth velocity can be comparable with or even larger than the solute diffusion velocity in the bulk phases, modeling of rapid solidification with non-equilibrium solute diffusion becomes quite an important topic. In this paper, an effective mobility approach was proposed to derive the current phase field model (PFM). In contrast with the previous PFMs that were derived by the so-called kinetic energy approach, diffusionless solidification happens not only in the bulk phases but also inside the interface when the growth velocity is equal to the solute diffusion velocity in liquid. A good agreement between the model predictions and experimental results is obtained for rapid solidification of Si-9at.%As alloy.

Abstract: The microstructure evolution during the directional solidification of Al-Cu alloy is simulated using a phase field model. The transformation from liquid to solid phase is a non-equilibrium process with three regions (liquid, solid and interface) involved. Phase field model is defined for each of the three regions. The evolution of each phase is calculated by a set of phase field equations, whereas the solute in those regions is calculated by a concentration equation. In this work, the phase field model which is generally valid for most kinds of transitions between phases, it is applied to the directional solidification problem. Numerical results for the morphological evolution of columnar dendrite in Al-Cu alloy are in agreement with experimental observations found in the literature. The growth velocity of the dendrite tip and the concentration profile in the solid, interface and liquid region were calculated.

Abstract: Numerical simulations of foam structure formation and destruction process were demonstrated using a phase field model. Two types of additional terms to control the cell size were introduced to the conventional multi-phase field model; one is to maintain the initial cell size, and the other is to adjust the size of neighboring cells to be equalized to each other. As a result, different types of foam structures were obtained according to the introduced effect of the extra terms. Destruction process was also simulated under simple assumptions; instantaneous bursts of cell wall occur intermittently at random sites, and the cell coarsening is accelerated when a certain time has passed. The intended variation was successfully observed, and the effectiveness of the model was confirmed.