Papers by Keyword: Microstructure Simulation

Abstract: To obtain an A356 aluminum alloy casting with a uniform structure and no internal shrinkage defects, ProCAST software is used to set different filling and solidification process parameters for an A356 aluminum alloy casting with large wall thickness differences, And multiple simulations are conducted to obtain optimized casting process; then, based on the process, the microstructure of the thickest and thinnest part of the casting are simulated. The size, morphology, and distribution of the simulated microstructure of the thinnest part and the thickest part of the casting are very similar. The simulated microstructure is similar to that of the actual casting. This shows that castings with uniform structure and no internal shrinkage defects can be obtained through the optimized casting process .

Abstract: Semi-solid aluminum slurries have globular grains, different from traditional dendritic solidification microstructures. The mechanism responsible for the formation of these globular grains is still in dispute. Some researchers suggest that the globular grains are formed by fractured dendrites, while others report it is due to copious nucleation. This study will model the growth of the α-Al phase during the production of semi-solid slurries using the swirled equilibrium enthalpy device (SEED) process, where liquid alloy with a low superheat is poured into a steel crucible and swirled within the semi-solid region. Experimental observations have shown that the final microstructure of the slurry produced by the SEED process is relatively non-uniform, with large dendrites at surface and fine spherical particles at the center. Open source code for the phase field method has been adopted to simulate the different microstructural evolution for semi-solid alloy 357.0. The effect of localized temperatures under isothermal condition on the morphology of the α-Al particles has been investigated according to the special conditions of the SEED process. In addition, suggestions for modifying the slurry production to achieve more uniform microstructure are discussed.

Abstract: Turbine disc is the key component of aviation engine, its performance is important to ensure the reliability and safety of the whole aviation engine. In this paper, forging forming of GH4169 alloy turbine disks of certain type aero-engine are discsimulated by DEFORM-3D soft system,these forming methods include next three kinds: common hot die forging, isothermal forging and composite sheath hot die forging.The influences of various forging ways on turbine disk forging quality and the used die are analyzed in order to find the most suitable way of forging. The forging defects in the forging process are analyzed . For basically eliminating these defects, the forging process of superalloy turbine disk are optimized based on the most economical and simple principles and some useful methds are gained，which will provide a reference to actual superalloy turbine disk forging process.

Abstract: The microstructure and material properties of AZ31 magnesium alloy are very sensitive to process parameters, which directly determine the service properties. To explore and understand the deformation behavior and the optimization of the deformation process, the microstructure evolution during equal channel angular pressing was predicted by using the DEFORM-3D software package at different temperature. To verify the finite element simulation results, the microstructure across the transverse direction of the billet was measured. The results show that the effects strain and deformation temperatures on the microstructure evolution of AZ31 magnesium during ECAP process are significant, and a good agreement between the predicted and experimental results was obtained, which confirmed that the derived dynamic recrystallization mathematical models can be successfully incorporated into the finite element model to predict the microstructure evolution of ECAP process for AZ31 magnesium.

Abstract: Constitutive equations and dynamic recrystallization (DRX) model of GH4169 alloy were investigated using compression tests with temperature 940(°C)-1060(°C) and strain rate 0.001(s-1)-0.1(s-1). A coupled numerical simulation between thermal-mechanical and microstructure evolution was realized through embedding the developed user subroutines into the FEM software DEFORM-3D system. The simulated results show that higher speed of upper die is useful to the DRX but much higher and lower speed of upper die go against improving the finer and uniform of grain size in the blade. Furthermore, the grains are finer and uniform in the blade body compared with those of blade rabbet and damper platform. The experimental results of microstructure under the same forging condition were studied and the average grain degrees in the blade are over 9. The calculated results of microstructure have a good agreement with the measured value from experimental data and the prediction error is less than 7.0%. Therefore, the DRX model and developed program is reliable to optimize and improve the parameters in the blade finish forging.

Abstract: Today almost all steel production fields use process models on the basis of analytic and numeric simulations. Planning and implementation of modern production in plants strategies can no longer be imagined without simulations in almost all fields of long and flat steel production. For the plant engineering and construction industry, planning of transformation processes and rolling mills can hardly be imagined without the use of modern simulation technology. The possibilities range from the simulation of material transformation behavior to the whole rolling process, extending to the load effected on units and plants as well as the projection of microstructure and material properties when applying different rolling technologies. Thus simulation models increasingly contribute to support future-oriented process development and material related optimization.

Abstract: Based on the microstructure results of Monte Carlo simulation, a three-dimensional grid model is built up, and imported into the finite element software with C++ language to analyze the mechanical properties of ceramic tool material. The stress field and residual stress of single-phase and multiphase ceramics have been analyzed by the computer simulation technology.

Abstract: Phase-field method can be used to describe the complicated morphologies of crystal growth without explicitly tracking the complex phase boundaries. The conformation of volume free energy is very important for microstructure simulation with phase-field method. However, the conformation of volume free energy is still correspondingly simple and ideal at present. In this paper, a new conformation method of free energy is mentioned. Free energy of each phase at appointed states is calculated by Thermo-Calc software. In order to avoided calculation, free energy of each phase is fitted by multiple-point function according to sub- regular solution model. It is obtained that the free energy data and phase graph data of α phase, θ phase and L phase in the extension, temperature (791-841) K and component (0-35)Cu(at.%) with Al-Cu eutectic alloy. The new phase model is also founded, and used to calculate microstructure evolution of Al-Cu eutectic alloy.

Abstract: Aluminum casting is widely used in aeronautical, automobile and other industries nowadays. The Cellular Automaton (CA) method was modified to simulate the microstructure evolution of Al alloy casting. Simulated program code was developed and applied into Al casting production. A nucleation model was investigated based upon the experimental data. The solute diffusion in the liquid and solid phases was also considered in developing a grain growth model. With the developed models, not only grain structure but also dendritic microstructure can be predicted during the solidification process. The microstructure simulation of the Al alloy turbine wheel was studied in detail.

Abstract: A cellular automaton (CA) based model for two-dimensional simulation of the grain morphology of high pressure die casting magnesium alloy was developed. The heterogeneous nucleation, the solute redistribution both in liquid and solid, the interface curvature and the growth anisotropy during solidification were also considered in the model. By fitting the curve of grain density distribution, parameters of continuous nucleation equation based on Gaussian distribution were calculated. The microstructure simulation of step-shape die castings of AM50 magnesium alloy was studied. The metallographic microstructure of the castings at the surface and center of three steps with different initial die temperature was investigated. The simulation results were compared with the experimental results and they were in good agreement on average grain size.