Phase field simulation of dendrite evolution during powderbased laser metal depositionстатья
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Дата последнего поиска статьи во внешних источниках: 31 июля 2019 г.
Аннотация:An algorithm for simulation of laser metal deposition (LMD) processes is developed,
which implements the concept of multi-scale modeling of crystallization. The macro-level model
takes into account the coupled dynamics of the free surface (melt-gas) and the energy and mass
transfer of the multiphase mixture, which is applied on scales of the order of a few to tens of
millimeters. The micro-level model describes the evolution of dendritic structures using the
phase-field method (PFM) at scales of the order of a few to tens of micro-meters. Wherein, the
resulting macroscopic temperature distribution in the system defines the boundary and initial
conditions of the micro-model, which, in turn, control the growth patterns and evolution of the
dendrites. In local sub-region, the evolution of the dendrite in an advantageous position was
simulated, i.e. having favorable thermodynamic conditions of its growth. Before solving the
micro-scale problem with the PFM, the 3D mesh conversion procedure to the new 2D mesh is
performed in the sub-region of interest. To do this, we select the plane in which the local
temperature gradient vector lies. The test dynamic profiles of the phase field and temperature in
different spatial regions of the formed bead are calculated. Simulations used the values of
physical quantities for iron. The results of calculations showed that the developed numerical
model qualitatively describes the physics of crystallization and the formation of dendrites in the
LMD process. The effect on the growth dynamics of dendritic structures of such PFM parameters
as thermal noise and the anisotropy amplitude is analyzed. It is shown that thermal fluctuations
strongly affect the branching of dendrites. With an increase in the fluctuation amplitude, the
phase boundary becomes unstable with the formation of secondary and tertiary branches.