An analytical solidification model for the columnar-to-equiaxed transition (CET) in rapid solidification was used to assess the microstructure variation within the melt-pool. The minimum value for the overall combined error, between the calculated values with the HTS_FD model and measured values for both the width and height of the melt-pool, was attained for a surface tension coefficient of -0.75e-4 N/m. Two sensitivity studies were conducted by varying the evaporation flux and the surface tension coefficient at fixed laser absorptivities of 0.5 and 0.3, respectively. For the keyhole regime case, numerical simulation results indicate that the melt-pool shape was typical to that of the conduction case with very large deviations from the measured melt-pool depths.
In order to validate Truchas for STLF and LPBFAM modeling, experimental data, which was obtained at GE Global Research (GEGR) for liquid pool shape and microstructure, were compared with those from numerical simulation results.
The results show that the more » fluid flow affects the solidification and ensuing microstructure in STLF. This study is one the first attempt to understand the effect of the fluid flow on microstructure in STLF and LPBFAM. In the HTS_FD model, the fluid flow was considered to be laminar while the molten alloy surface is assumed to be flat and non-deformable. In order to assess the effect of the fluid dynamics on the solidification and ensuing microstructure, a heat transfer-and-solidification-only (HTS) model and a fully coupled heat-transfer-solidification and fluid-dynamics (HTS-FD) model were considered. Multi-physics simulations were conducted using Truchas for STLF by considering heat transfer, phase-change, fluid dynamics, surface tension phenomena, and evaporation. As a critical step towards fully LPBFAM modeling, modeling of single-track laser fusion (STLF) were conducted. In this project, a multi-physics model was developed on a highly parallel open-source code, Truchas, with the ultimate goal of providing experimentally validated process maps for tailoring microstructure to achieve desired performance for LPBFAM. At present, the cost and time associated with LPBFAM process development is very high due to a lack of fundamental process understanding. The proposed algorithm also has a higher convergence speed in achieving optimal blank.The Laser Powder Bed Fusion Additive Manufacturing (LPBFAM) is one of the most important processes for the production of lightweight, cost-effective, complex, and high-performance enduse parts. Because in other algorithms presented in the articles, if the appropriate initial guess is not selected, the algorithm will not converge to the answer.
The results showed that the proposed algorithm is sufficiently robust against the initial guesses for the blank, which is an advantage of the present algorithm over those from other algorithms. Next, an example problem was solved, and the results are compared with other studies.
A computer program was developed to automatically run these iterations to study the features of the proposed algorithm. The present study implements a similar approach and presents a new algorithm to make geometrical corrections to the external boundaries of a blank, as well as its internal boundaries, in several iterations. Therefore, the general solution to such problems is to use iterative methods based on numerical simulation. The deep drawing process is highly nonlinear due to the large deformation, plastic deformation of the material and the contact phenomenon. In the deep drawing process, the optimal design of the initial blank shape has many advantages such as reducing the cost of production and waste and improving the quality of the process and thickness distribution.