Additive Manufacturing Modeling and Simulation: AM Materials, Processes, and Mechanics: Additive Manufacturing Modeling and Simulation - Microstructure Evolution
Sponsored by: TMS Additive Manufacturing Committee
Program Organizers: Jing Zhang, Indiana University – Purdue University Indianapolis; Brandon McWilliams, US Army Research Laboratory; Li Ma, Johns Hopkins University Applied Physics Laboratory; Yeon-Gil Jung, Korea Institute of Ceramic Engineering & Technology
Monday 8:00 AM
November 2, 2020
Room: Virtual Meeting Room 2
Location: MS&T Virtual
Session Chair: Jing Zhang, Indiana University - Purdue University Indianapolis; Brandon McWilliams, CCDC Army Research Laboratory; Li Ma, Johns Hopkins University Applied Physics Laboratory; Yeon-Gil Jung, Changwon National University
8:00 AM Keynote
A Discrete Dendrite Dynamics Model for Fast Epitaxial Columnar Grain Growth in Metal Additive Manufacturing: Santanu Paul1; Yunhao Zhao1; Soumya Sridar1; Wei Xiong1; Michael Klecka2; Albert To1; 1University of Pittsburgh; 2United Technologies Research Center
In this work, an efficient model called Discrete Dendrite Dynamics (DDD) is proposed to simulate the competitive growth of epitaxial columnar dendritic grains. The proposed model tracks the dynamic changes in the dendrites emanating from discrete points along the solid/liquid interface of a quasi-steady melt pool. Additionally, the branching mechanism due to change in the primary dendrite growth direction is also included in the model. The model is extended to predict the microstructure of large 3D parts and experimentally validated by comparing the simulation results for Laser Powder Bed Fusion (LPBF) and Wire-Arc Additive Manufacturing (WAAM) processes. The microstructure and pole figures are predicted for Inconel 718 samples produced by LPBF and Inconel 740H samples produced by WAAM processes. A good match between the prediction and experiments is observed for the microstructure and pole figures for both the LPBF and WAAM processes.
8:40 AM Invited
Cellular Automata Modeling of Microstructure Resulting from Novel Scan Patterns in Selective Laser Melting: Matthew Rolchigo1; Benjamin Stump2; Alex Plotkowski2; James Belak1; 1Lawrence Livermore National Laboratory; 2Oak Ridge National Laboratory
Cellular automata (CA) methods have successfully modeled grain characteristics and texture development during traditional linear scan patterns during Additive processing. This work focuses on solidification resulting from both linear and more complex scan patterns, such as multi-spot scans, often used in attempts to control columnar grain growth. Using temperature data calculated using the CFD software OpenFOAM, along with the GPU-accelerated ExaCA code for solidification modeling, we examine texture development and competitive nucleation and growth using a variety of novel scan patterns. The CA model ability to predict experimental microstructural trends, and its potential future use in conjunction with melt pool modeling for engineering scan patterns for desired grain structures will also be discussed. *Work performed under auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344, and supported by ECP (17-SC-20-SC), a collaborative effort of U.S. DOE Office of Science and NNSA.
9:00 AM Invited
Transient Evolution of Columnar Dendrites during Additive Manufacturing – Implications for Process Simulations: Bala Radhakrishnan1; Younggil Song1; Alex Plotkowski1; Gerald Knapp1; John Turner1; 1Oak Ridge National Laboratory
During additive manufacturing of structural alloys, columnar dendritic microstructures are formed under certain temperature gradients (G) and growth rates (R). Whenever a new layer of liquid metal begins to solidify on top of a substrate, formation of a constitutionally undercooled region ahead of the solid-liquid (s-l) interface through solute enrichment to attain a steady-state value of R for a given G, as defined in analytical models, is not attained instantaneously. We demonstrate through phase field simulations in a Ni-Fe-Nb alloy that the non-steady state portion of the evolution could become significant enough to introduce potential errors when a steady state approximation is assumed in simulating the microstructure evolution. The implications for predictive processing-microstructure simulations during additive manufacturing are discussed. Research supported by the Department of Energy's Exascale Computing project at the Oak Ridge National Laboratory under contract DE-AC05-00OR22725. The simulations were performed using the Oak Ridge Leadership Class computing facilities.
9:20 AM
Phase Field Simulations of Solid-state Precipitation in AM-processed 625 and 718 Alloys during Post-process Annealing: Bala Radhakrishnan1; Younggil Song1; Sarma Gorti1; Steve DeWitt1; John Turner1; Lyle Levine2; Ranadip Acharya3; William Tredway3; Amrita Basak4; Tanjheel Mahdi4; 1Oak Ridge National Laboratory; 2National Institute of Standards and Technology; 3United Technologies Research Corporation; 4Pennsylvania State University
We present large scale, phase field simulations of microstructure evolution during post-processing of 718 and 625 alloys produced by laser powder bed fusion additive manufacturing. The simulations capture the effect of micro segregation of alloying elements on the growth kinetics and morphology of co-precipitating phases - gamma', gamma" and delta as a function of annealing schedule. The simulations will also capture the effect of partial dissolution of the Laves phase in the as-solidified microstructure on the precipitation structure during subsequent aging. The objective of the simulations is to optimize the post-process heat treatment in these alloys to meet target properties. The simulation results are validated using results of advanced characterization performed on the AM-processed materials. Research supported by the Department of Energy's HPC4EI program and the Exascale Computing project at the Oak Ridge National Laboratory. The simulations were performed using the Oak Ridge Leadership Class computing facilities.
9:40 AM
Modeling Hot Cracking in Metal Additive Manufacturing: Eric Clough1; Brennan Yahata1; Mark O'Masta2; Hunter Martin2; Matt Begley3; 1University of California, Santa Barbara / HRL Laboratories; 2HRL Laboratories; 3University of California, Santa Barbara
Additive manufacturing has the potential to drastically alter the design and fabrication of metal parts by enabling complex geometries, and eliminating the need to develop expensive tooling. Unfortunately, the alloys that are currently printable via additive manufacturing preclude many engineering-relevant structural metals. A key reason that many of these structural metals are deemed unprintable is their tendency to crack while solidifying and cooling. Solidification conditions that tend to form crack-susceptible microstructures, combined with a limited ability to add filler-metal to compensate for solidification shrinkage, pose a significant challenge in additive manufacturing of alloys prone to hot cracking.In this seminar we will present a multi-physics framework for simulating hot cracking accounting for fluid flow, solid mechanics, interfacial phenomena, and phase transformations. Through improved understanding of the mechanics of hot cracking, we aim to develop general concepts for mitigating hot cracks via optimal processing parameter selection and simulation-informed alloy design.