Dissertation
Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Metallographic microstructure and properties of the (metal )

Numerical Simulation of Dendritic Growth of NI-CU Binary Single-phase Alloys Using a Phase-field Method

Author YuanHai
Tutor XueXiang
School Harbin Institute of Technology
Course Materials Processing Engineering
Keywords Solidification Microstructure Phase-field method Dendrite growth Numerical Simulation
CLC TG113
Type Master's thesis
Year 2010
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Numerical simulation of microstructure of metallic materials development and application of great significance, but also the computer used in the field of materials science major development directions. Numerical Simulation of Microstructure main methods: deterministic methods, stochastic methods and phase field method. Where the phase-field method is used to describe the non-equilibrium state in the complex evolution of the phase interface powerful tool, no need to track complex solid-liquid interface, you can achieve analog metal dendrite growth during solidification of complex topography, is currently solidification simulation development in the area. In this paper, phase-field method for alloy dendrite growth during solidification was simulated, in-depth study of the solidification process of dendritic growth mechanism for the eventual realization of the mechanical properties of castings forecast has laid a good foundation. Based on a uniform grid finite difference equations, when used in a double mesh grid method. Numerical calculation, in order to avoid restrictions on the time step, the temperature control equation is used alternating direction implicit method (ADI algorithm); and the use of narrow-band solid-liquid interface method and the solute diffusion layer boundary method captures two methods jointly optimize phase-field model numerical algorithm, greatly reducing the computation to improve the computational efficiency. In isothermal solidification conditions, simulated Ni-Cu binary alloy solidification process equiaxed dendrite growth and evolution; reproduced equiaxed dendritic growth of lateral branches competitive growth, maturation process and solute segregation. Neumann boundary conditions using temperature alloy dendritic growth of non-isothermal simulations to study the undercooling on dendrite growth simulation effects with decreasing temperature, the faster the growth of dendrites, secondary dendrite Crystal arm more developed dendritic segregation of solute more serious, but when the temperature dropped to a critical temperature 1569K, the micro-segregation decreased rapidly. Unlike the simulation results of multi-grain single grain dendrite contact with each other after the receipt of dendrite growth inhibition, bend, dendrite longer symmetrical, continuous nucleation model of multi-grain simulation results with the real situation is more approximation. Directed planar interface under the initial instability occurs, dendrite formation, cellular spacing gradually adjusted, the final stable growth cellular spacing is approximately 1.8μm. With the initial temperature decreases gradually from the interface to the cellular dendrite columnar crystal planar interface and then evolve.

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