- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Microstructure modelling of laser metal powder directed energy deposition of Alloy 718
摘要： A multi-component and multi-phase-field modelling approach, combined with transformation kinetics modelling, was used to model microstructure evolution during laser metal powder directed energy deposition of Alloy 718 and subsequent heat treatments. Experimental temperature measurements were utilised to predict microstructural evolution during successive addition of layers. Segregation of alloying elements as well as formation of Laves and δ phase was specifically modelled. The predicted elemental concentrations were then used in transformation kinetics to estimate changes in Continuous Cooling Transformation (CCT) and Time Temperature Transformation (TTT) diagrams for Alloy 718. Modelling results showed good agreement with experimentally observed phase evolution within the microstructure. The results indicate that the approach can be a valuable tool, both for improving process understanding and for process development including subsequent heat treatment.
关键词： Modelling,Heat Treatment,Phase-field,Thermal Cycle,DED
更新于2025-11-21 11:18:25
-
A non-isothermal phase-field model for piezo–ferroelectric materials
摘要： We propose a model for the study of piezo–ferroelectric materials, based on the Ginzburg–Landau approach to the ferroelectric transition, in which the inelastic deformation is a direct function of the ferroelectric polarization. The non-isothermal effects related to the phase change and other dissipative phenomena are considered by a suitable energy balance equation, according to the restrictions of the second principle. The hysteresis phenomena for polarization and inelastic strain are considered from both the energetic perspective of the vector Ginzburg–Landau equation and the dissipation-dominated perspective of the rate-independent evolutionary equations.
关键词： Ferroelectric,Phase field,Ferroelastic,Non-isothermal model,Hysteresis
更新于2025-09-23 15:22:29
-
Phase field modeling of grain boundary migration and preferential grain growth driven by electric current stressing
摘要： A phase field model incorporating the electrostatic free energy and the grain orientation effect is developed and employed to study the grain boundary migration and preferential grain growth in widely used beta-tin (β-Sn) under electric current stressing. The directional migration of grain boundaries and the preferential growth of the grain with its orientation having low electrical resistivity along the electric current direction are theoretically clarified. In a bicrystal system containing a circular grain, the shrinkage velocity and morphology changes of grains are dominated by the competition effect between the grain boundary energy and the electrostatic free energy; in particular, the high-density electric current can induce the instability of grain morphology evolution. Moreover, grain morphology evolution leads to the change of the voltage across the β-Sn system; it is found that the voltage decreases over time in a tricrystal system, while the variation of the voltage across the bicrystal system is related to the above-mentioned competition effect. The proposed model and results provide insights into the orientation-related microstructure evolution under electric current stressing.
关键词： preferential grain growth,electric current stressing,microstructure evolution,grain boundary migration,beta-tin,phase field model
更新于2025-09-23 15:21:21
-
Computational study of nonlinear dielectric composites with field-induced antiferroelectric-ferroelectric phase transition
摘要： Electric field-induced antiferroelectric-ferroelectric phase transition and the associated nonlinear dielectric behavior in particulate composites are investigated for achieving a high dielectric capacity. A phenomenological thermodynamic model based on the Landau theory is first developed to discuss the generic phenomena of a temperature-electric field phase diagram, coexistence of antiferroelectric and ferroelectric phases, field-induced antiferroelectric-ferroelectric phase transition, and nonlinear dielectric behavior. The model is then used to carry out the phase field simulation of particulate nonlinear dielectric composites. It is found that the composites exhibit nonlinear dielectric behaviors, and the depolarization field in the composites helps reduce the dielectric hysteresis and enhance the reversibility of antiferroelectric-ferroelectric phase transitions, which are desired for energy storage applications. The simulations also reveal the underlying domain-level mechanisms for nucleation and growth processes of the phase transitions. It is shown that the macroscopic properties of the composites sensitively depend on the directional alignment of the antiferroelectric filler particles, and thus the filler morphology is an effective control variable in designing nonlinear dielectric composites.
关键词： phase field simulation,energy storage,nonlinear dielectric composites,Landau theory,antiferroelectric-ferroelectric phase transition
更新于2025-09-23 15:21:01
-
Simulation-assisted analysis of microstructural evolution of Tia??6Ala??4V during laser powder bed fusion
摘要： A combination of a Multi-Phase Field model and an Orientation Field is proposed to describe the microstructure evolution induced by laser–material interaction in Laser Powder Bed Fusion (LPBF). The relevant phase transformations are covered by nucleation and growth processes driven by free enthalpy. An empiric correction is applied to the phase-field approach to reduce the grid resolution required for the numerical simulation. This contribution focuses on the LPBF processing of the titanium alloy Ti–6Al–4V. Particularly, the transition between β-titanium and melt is emphasized. The results are discussed and compared to measurements. A numerical correction can be applied to the MPF model to avoid a mesh introduct anisotopy in the crystal growth. The simulation shows the β-phase crystal growth with the (1 0 0) direction into the melt. The model for the phase transformation from β-phase to α-phase agrees with the XRD measurements.
关键词： Simulation,Orientation field method,Phase-field method,Selective laser melting,Volume of the fluid method,Laser powder bed fusion
更新于2025-09-23 15:19:57
-
Phase-field modeling of domain evolution in ferroelectric materials in the presence of defects
摘要： The properties of ferroelectric devices are strongly influenced, besides crystallographic features, by defects in the material. To study this effect, a fully coupled electromechanical phase-field model for 2D ferroelectric volume elements has been developed and implemented in a Finite Element code. Different kinds of defects were considered: holes, point charges and polarization pinning in single crystals, as well as grain boundaries in polycrystals, without and with additional dielectric interphase. The impact of the various types of defects on the domain configuration and the overall coercive field strength is discussed in detail. It can be seen that defects lead to nucleation of new domains. Compared to the energy barrier for switching in an ideal single crystal, the overall coercive field strength is significantly reduced towards realistic values as they are found in ferroelectric devices. Also the simulated hysteresis loops show a more realistic shape in the presence of defects.
关键词： polycrystalline ferroelectric,phase-field modeling,microstructural defects
更新于2025-09-19 17:15:36
-
Investigation on Ti-6Al-4V Microstructure Evolution in Selective Laser Melting
摘要： Selective laser melting (SLM) is an advanced additive manufacturing technique that can produce complex and accurate metal samples. Since the process performs local high heat input during a very short interaction time, the physical parameters in the solidification are difficult to measure experimentally. In this work, the microstructure evolution of Ti-6Al-4V alloy in additive manufacturing was studied. With the increase of scanning speed, the cooling rate and the temperature gradient of molten pool position increased, which was attributed to the gradual decrease of energy density. The phase-field simulation resulted in the overall microstructure morphology of columnar crystals owing to the very large temperature gradient and cooling rate obtained from the temperature field. Microsegregation was observed during dendritic formation, and the solute was enriched in the liquid phase near the dendritic tip and between the dendritic arms due to the lower equilibrium distribution coefficient. The scanning speed had an effect on the dendrite spacing.
关键词： phase field,microstructure,SLM,simulation
更新于2025-09-19 17:13:59
-
Coupled phase‐field modeling of domain and fracture evolution in anisotropic ferroelectric ceramics
摘要： The contribution presents a material model for the simulation of domain and fracture evolution in ferroelectric ceramics. Ferroelectric domains and cracks are modeled by using a phase field. While for the modeling of the ferroelectric domains we consider the vectorial electric polarization as order parameter, the modeling of cracks is based on a scalar damage variable. In the present contribution, we discuss the evolution of domains and cracks in an anisotropic ferroelectric solid.
关键词： domain evolution,ferroelectric ceramics,fracture evolution,phase-field modeling,anisotropy
更新于2025-09-16 10:30:52
-
Process-Structure-Properties-Performance Modeling for Selective Laser Melting
摘要： Selective laser melting (SLM) is a promising manufacturing technique where the part design, from performance and properties process control and alloying, can be accelerated with integrated computational materials engineering (ICME). This paper demonstrates a process-structure-properties-performance modeling framework for SLM. For powder-bed scale melt pool modeling, we present a diffuse-interface multiphase computational fluid dynamics model which couples Navier–Stokes, Cahn–Hilliard, and heat-transfer equations. A computationally efficient large-scale heat-transfer model is used to describe the temperature evolution in larger volumes. Phase field modeling is used to demonstrate how epitaxial growth of Ti-6-4 can be interrupted with inoculants to obtain an equiaxed polycrystalline structure. These structures are enriched with a synthetic lath martensite substructure, and their micromechanical response are investigated with a crystal plasticity model. The fatigue performance of these structures are analyzed, with spherical porelike defects and high-aspect-ratio cracklike defects incorporated, and a cycle-amplitude fatigue graph is produced to quantify the fatigue behavior of the structures. The simulated fatigue life presents trends consistent with the literature in terms of high cycle and low cycle fatigue, and the role of defects in dominating the respective performance of the produced SLM structures. The proposed ICME workflow emphasizes the possibilities arising from the vast design space exploitable with respect to manufacturing systems, powders, respective alloy chemistries, and microstructures. By digitalizing the whole workflow and enabling a thorough and detailed virtual evaluation of the causal relationships, the promise of product-targeted materials and solutions for metal additive manufacturing becomes closer to practical engineering application.
关键词： heat-transfer modeling,additive manufacturing,phase field modeling,integrated computational materials engineering,crystal plasticity,selective laser melting,micromechanical modeling
更新于2025-09-16 10:30:52
-
Understanding and predicting geometrical constraint ferroelectric charged domain walls in a BiFeO <sub/>3</sub> island via phase-field simulations
摘要： It has been known that ferroelectric charged domain walls (CDWs), which break the polarization continuity, may be electrically active with an elevated conductivity. However, the bound charge at CDWs may render them energetically unstable, and thus, forming CDWs naturally and manipulating them electrically is still challenging. Here, we theoretically utilize phase-field simulations to design spontaneously generated CDWs with center-type quad-domains in a single square-shaped BiFeO3 nanoisland. It is shown that the stability of the spontaneously emerging head-to-head domain walls with center-convergent quad-domains is mainly determined by three contributions, namely, the geometrical constraint from approximately 45°-tilted bottom edges, the electric boundary condition, and the necessary screening free charges to compensate head-to-head domain walls. It is demonstrated that the center-convergent quad-domains with head-to-head CDWs can be electrically switched to the center-divergent one with tail-to-tail CDWs, providing guidance for achieving ferroelectric domain-wall-based nanodevices with low-power dissipation.
关键词： phase-field simulations,electric boundary condition,ferroelectric charged domain walls,BiFeO3,screening free charges,geometrical constraint
更新于2025-09-10 09:29:36