Additive Manufacturing: Processing Effects on Microstructure and Material Performance: Solidification
Sponsored by: TMS: Additive Manufacturing Committee
Program Organizers: Eric Lass, University of Tennessee-Knoxville; Joy Gockel, Wright State University; Emma White, DECHEMA Forschungsinstitut; Richard Fonda, Naval Research Laboratory; Monnamme Tlotleng, University of Johannesburg; Jayme Keist, Pennsylvania State University; Hang Yu, Virginia Polytechnic Institute And State University
Tuesday 8:30 AM
February 25, 2020
Room: 6E
Location: San Diego Convention Ctr
Session Chair: Richard Fonda, Naval Research Laboratory; Amrita Basak, Pennsylvania State University
8:30 AM
Applying Computational Modeling to Non-equilibrium Solidification: Eric Heikkenen1; Sudarsanam Babu1; 1The University of Tennessee
Combining computational thermodynamic modeling, numeric heat transfer simulation, and interface response function models allows for the potential control of microstructural features and resulting mechanical properties, especially when considering rapid, non-equilibrium solidification commonly encountered in additive manufacturing. When combined with mechanical testing and metallography, modeling and simulation results can be rationalized to real world results. As an example, the yield strength of aluminum silicon alloys can be controlled through manipulating the input of energy. This technique could allow yield strength to be uniquely varied throughout an additively manufactured part. Additionally, the technique could be used to optimize process parameters to yield desired microstructures while limiting potentially deleterious phases such as delta ferrite in additively manufactured steels.
8:50 AM
Phase Field Modeling of Alloy Microstructure Formation in Rapidly Solidifying Melt Pools: Joel Berry1; Aurelien Perron1; Jean-Luc Fattebert2; Saad Khairallah1; Joseph McKeown1; Manyalibo Matthews1; 1Lawrence Livermore National Laboratory; 2Oak Ridge National Laboratory
The ability to tailor and spatially grade material properties during manufacturing opens a vast design space and flexibility in component optimization with respect to size, weight, shape, etc. Laser-based additive manufacturing (AM) of metal alloys offers the potential for spatial control of microstructure and thus material properties, but requires quantitative relations between laser beam characteristics and resultant metal microstructure. Toward this aim, we quantitatively simulate crystal growth kinetics and microstructure formation in metal alloy melt pools using CALPHAD-informed phase field simulations with thermal profile input from high-fidelity multiphysics simulations. Solid phase growth mode (planar, cellular, dendritic), compositional segregation, and characteristic microstructural length scales are mapped as functions of external process parameters and compared with experimental observations and measurements. Transfer of these results to laser powder-bed fusion AM with spatial microstructural control will be discussed. Prepared by LLNL under Contract DE-AC52-07NA27344 and supported by the LDRD Program, project tracking code 18-SI-003.
9:10 AM
Phase-field Solidification Texture Model for Understanding the Microstructure in L-PBF Process: Kamalnath Kadirvel1; Guilherme Abreu Faria1; Xuesong Gao1; Antonio Rameriz1; Wei Zhang1; Yunzhi Wang1; 1Ohio State University
Laser-Powder Bed Fusion (L-PBF) is a commonly used method in metal additive-manufacturing (AM). One of the key microstructural features, which affects the mechanical property of the AM product, is the solidification grain texture. We have developed a phase-field model (PFM) which is coupled with a heat-flux model to predict the grain texture in the L-PBF process. Our PFM incorporates the solidification at the melt pool interface, anisotropic mobility of the solid-liquid interface, re-solidification due to multiple laser passes and possible grain-growth near the melt pool. Temperature profile calculated from AM processing parameters such as laser beam power and beam velocity were used as input to the PFM simulations. The simulated texture was compared with EBSD characterization of an AM build IN718 Ni-based superalloy. The model was used to study the effect of different laser scan patterns on the solidification texture.
9:30 AM
Phase Field Simulation of Solidification Behavior of AlSi10Mg Alloys Manufactured Through Direct Metal Laser Sintering: Hossein Azizi1; Alireza Ebrahimi1; Nana Ofori-Opoku2; Michael Greenwood3; Nikoas Provatas4; Mohsen Mohammadi1; 1University of New Brunswick; 2Canadian Nuclear Laboratories; 3Natural Resources of Canada; 4McGill University
In this work we numerically investigate the effect of building direction on the solidification behaviour and microstructure evolution of direct metal laser sintered (DMLS) AlSi10Mg. The building direction, as previously proved in experimental studies, can influence the solidification behavior and promote morphological transitions in cellular dendritic microstructures such as columnar-to-equiaxed transition (CET). We develop a thermal model to systemically address the impact of laser processing conditions, as well as building direction on time-dependent solidification parameters including pulling velocity, thermal gradients, and cooling rates of the molten pool during DMLS of AlSi10Mg alloy. We then study the microstructure evolution of DLMS-AlSi10Mg for horizontal and vertical building directions. The present model includes a heterogenous nucleation of inoculant particles that triggers the CET and its results are consistent with the predictions of a previously developed model. In addition, we compare our findings with experimental observations to ensure the accuracy of our results.
9:50 AM Cancelled
Multiscale Modeling of Metal Additive Manufacturing: Linking of Continuum Scale CFD and Mesoscale Phase-field Models: Patrick O'Toole1; Milan Patel2; Paulus Lahur1; Dayalan Gunasegaram1; Anthony Murphy1; Ivan Cole2; Chao Tamg3; Ming Gan3; Chee Wong3; 1CSIRO; 2RMIT University; 3Nanyang Technological University
We present results from a simulation of the Selective Laser Melting (SLM) process of AlSi10Mg alloy where the temperature histories output by a continuum scale computational fluid dynamics (CFD) model was used as input for a mesoscale phase field (PF) model that simulated microstructure evolution. We also discuss the features of a novel linkage scheme that was developed using an open-source CFD library and an open-source PF library. This scheme facilitated the efficient transfer of information from the higher scale to the lower scale with an acceptable loss in resolution. In doing so, it overcame some critical barriers to multiscale modeling which prevented software codes at different scales from communicating with each other effectively owing to their use, through necessity, of unique discretization and solution schemes.
10:10 AM Break
10:30 AM
Integrated Simulation Framework for Additively Manufactured Metallic Alloys: Rongpei Shi1; Saad Khairallah1; Tae Wook Heo1; Tien Roehling1; John Roehling1; Joseph Mckeown1; Manyalibo Matthews1; 1Lawrence Livermore National Laboratory
To accelerate the establishment of fundamental understanding of the additive manufacturing (AM) process and its influence on microstructural evolution and related properties of metallic alloys, we develop a multiphysics and multiscale modeling framework that integrates: (1) a high-fidelity powder-scale three dimensional simulation of transient heat transfer and melt flow dynamics, (2) cellular automaton simulation of solidification grain structure and texture, (3) phase-field modeling of precipitation and dissolution of second-phase precipitate during repeated thermal cycles, and (4) microstructure based mesoscopic elastic response calculation. We demonstrate the application of the integrated framework in: (1) laser beam shaping for solidification grain structure (i.e., columnar vs equiaxed grains) control during laser powder bed fusion (LPBF) AM of 316L-stainless steel; and (2) in situ selective large-area diode surface heating for both solidification grain structure and solid-state second-phase precipitate microstructure control during LPBF AM of Ti-6Al-4V.
10:50 AM
Directional Solidification Microstructure of Inconel 718 Manufactured by Electron Beam Additive Manufacturing: Changwoo Lee1; Byoung Soo Lee1; Hyung Giun Kim1; Gun Hee Kim1; 1Ki Tech
Directional solidification microstructure (DSM) of Inconel 718, manufactured by electron beam (EB) additive manufacturing (AM) processing, was studied. DSM was controlled by focus offset current during the EB processing, and the properties of building product were evaluated in various processing conditions. Comparing to other recent reports about Inconel EM products, the building product has not only the highest level tensile strength about 1300 MPa at room temperature but also the highest level of elongation of about 25%. It is related to precipitation and grain direction. The precipitation size was increased with an increased focus offset current, and very good directional microstructure could be obtained in optimum focus offset condition. These DSM had an excellent effect on creep property, and the creep lifetime increased about 4 times comparing aged wrought product.
11:10 AM
Microstructural Evolution of Additively Manufactured Inconel 718: Laura Farris1; E. Lee1; Judy Schneider1; 1University of Alabama in Huntsville
Inconel 718 (IN718) is a precipitation strengthened, nickel-based superalloy that is used in the Additive Manufacturing (AM) of low volume, complex parts. Rapid melting, solidification, and reheating during AM process exposes the material to non-equilibrium conditions affecting the phases formed. During solidification, the Niobium (Nb) can segregate into carbide, Laves or δ phases leaving an insufficient amount of Nb necessary for the formation of strengthening phases (g’ and g”). Knowledge of initial phase formation and their critical temperatures is essential to optimize heat treatment cycles that will resolutionize solidification phases and promote strengthening during aging treatments. Various experimental characterization techniques are used in this study to evaluate phases formed in IN718 fabricated by powder bed fusion (PBF) for both as-build and post heat-treated conditions. Critical equilibrium temperatures for secondary phase formation are computationally modeled and compared to experimental results. The current model only focuses on thermodynamic equilibrium and does not include kinetics of change.
11:30 AM
Solidification and Grain Formation During Additive Manufacturing Process: A Grandpotential Based Phase Field Study: Sudipta Biswas1; Larry Aagesen1; 1Idaho National Laboratory
Solidification play a significant role in dictating the microstructure formation during the additive manufacturing processes. Depending on the process conditions, it determines the formation of the grain structure that govern the properties and performance of the final manufactured components. Hence, understanding the solidification and associated microstructural evolution during additive manufacturing is of immense importance. The current work aims at capturing the morphological alterations a material undergoes during the laser additive manufacturing process. To this end, a grandpotential based phase field model has been implemented using a multiphysics framework. The model captures the effect of solute concentration as well as temperature during solidification of an alloy system. The model has been verified with observations made in existing literatures. The model also demonstrates how the process conditions influence the material morphology during the additive manufacturing process. It effects the formation of columnar, cellular, or equiaxed grains and transition between the said structures.