Solidification simulation of direct energy deposition process by multi-phase field method coupled with thermal analysis

Abstract

The multi-phase field method coupled with the thermodynamics database of calculation of phase diagrams has been successfully applied to simulation of solidification microstructure evolutions in engineering casting processes. As multi-phase field method is based on the local (quasi-)equilibrium assumption in solidification theory [1], applying this method to solidification of additive manufacturing processes is not studied enough because of extremely large cooling rate and temperature gradient conditions. On the other hand, some researchers have reported experimental observations of the columnar-to-equiaxed transition in the solidification of the additive manufacturing processes including the direct energy deposition. They suggest that the local (quasi-)equilibrium assumption can be applied to solidification of additive manufacturing processes [2]. In this study, solidification microstructures of titanium alloys in direct energy deposition are calculated by multi-phase field method. Temperature distributions obtained by thermal analyses using finite element method are adapted to multi-phase field method. The microstructure evolution of columnar-to-equiaxed transition is confirmed. The results are summarized in a solidification map for direct energy deposition process conditions.

Non- and Quasi-Equilibrium Multi-Phase Field Methods Coupled with CALPHAD Database for Rapid-Solidification Microstructural Evolution in Laser Powder Bed Additive Manufacturing Condition

“…Many Finite Element Method (FEM) analyses have been performed to show the temporal temperature distributions around a moving laser spot [8][9][10]. Furthermore, Computational Fluid Dynamics (CFD) analyses have been performed to obtain not only the temperature distribution but also the fluid flow in the melt pool by considering the free surface affected by Marangoni convection.…”

Preface for MMM 2018 focus issue

“…The present focus issue contains 25 original peer-reviewed papers, which show the very broad range of scales covered by the researches presented in MMM 2018. The major contributions are related to the Phase Field method [1-10] and Molecular Dynamics simulations [11][12][13][14] with the potential generation process [15], which have resolved the large-scaled crystallization [8,9], grain boundary migration [12], yielding of metals [16], and processing [3,5]. These fundamental phenomena need the huge length and time-scales.…”