Additive Manufacturing of Metals: Applications of Solidification Fundamentals: Solidification of Advanced Materials III
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Solidification Committee
Program Organizers: Wenda Tan, The University of Michigan; Alex Plotkowski, Oak Ridge National Laboratory; Lang Yuan, University of South Carolina; Lianyi Chen, University of Wisconsin-Madison
Thursday 2:00 PM
March 23, 2023
Room: 21
Location: SDCC
Session Chair: Alex Plotkowski, Oak Ridge National Laboratory
2:00 PM
The Effect of Thermoelectric Magnetohydrodynamics on Microstructure Evolution in Additive Manufacturing: Andrew Kao1; Xianqiang Fan2; Catherine Tonry1; Peter Soar1; Peter Lee2; Koulis Pericleous1; 1University of Greenwich; 2UCL
Melt pools formed in laser additive manufacturing (AM) are subject to large thermal gradients, resulting in the formation of thermoelectric currents. These currents interact with magnetic fields generating a Lorentz force which drives fluid flow. This phenomenon, known as Thermoelectric Magnetohydrodynamics (TEMHD) significantly impacts the melt pool morphology and microstructural evolution. TESA (ThermoElectric Solidification Algorithm) is a bespoke, parallel multi-scale code that solves rapid microstructure solidification with fluid flow and thermoelectric currents, capable of capturing the fully coupled process over multiple layers. The system is highly dependent on the orientation and strength of the magnetic field with competition between Marangoni flow and TEMHD resulting in control of the depth, width and potential deflections of the melt pool. This leads to significant changes in the microstructure including modification to the melt pool boundary layer and epitaxial growth. The numerical predictions compare favourably to Xray synchrotron experiments.
2:20 PM
Phase Transformation Dynamics Guided Alloy Development for Additive Manufacturing: Qilin Guo1; Minglei Qu1; Chihpin Andrew Chuang2; Lianghua Xiong3; Ali Nabaa1; Zachary Young1; Yang Ren2; Peter Kenesei2; Fan Zhang4; Lianyi Chen1; 1University of Wisconsin Madison; 2Argonne National Laboratory; 3Missouri University of Science and Technology; 4National Institute of Standards and Technology
Fusion-based additive manufacturing technologies enable the fabrication of geometrically and compositionally complex parts unachievable by conventional manufacturing methods. However, the non-uniform and far-from-equilibrium heating/cooling conditions pose a significant challenge to consistently obtaining desirable phases in the as-printed parts. Here we report a martensite stainless steel development guided by phase transformation dynamics during solidification revealed by in-situ high-speed, high-energy, high-resolution X-ray diffraction. This developed stainless steel consistently forms desired fully martensitic structure across a wide range of cooling rates (102–107 ℃/s), which enables direct printing of parts with fully martensitic structure. The as-printed material exhibits a yield strength comparable to its wrought counterpart after precipitation-hardening heat-treatment. The as-printed property is attributed to the fully martensitic structure and the fine precipitates formed during the intrinsic heat-treatment in additive manufacturing. The phase transformation dynamics guided alloy development strategy demonstrated here opens the path for developing reliable, high-performance alloys specific for additive manufacturing.
2:40 PM
Solidification Cracking Behaviour of AA 6061 Aluminium Alloy with Heated Substrate in Laser Powder Bed Fusion Additive Manufacturing: Sivaji Karna1; Rimah Al-Aridi1; Tianyu Zhang1; Timothy Krentz2; Dale Hitchcock2; Andrew Gross1; Lang Yuan1; 1University of South Carolina; 2Savannah River National Laboratory
Solidification cracking that occurs while printing AA 6061 aluminium alloy with laser powder bed fusion significantly limits printing of this otherwise popular alloy. Cubic samples were printed with varying laser power, scanning speed, and hatch spacing to investigate the process-structure relationship for solidification cracking. Best conditions were selected based on the relative density and the effect of a heated substrate was investigated. The cracks and as-built microstructures were characterized by optical and scanning electron microscopy. The number of cracks and crack morphology are quantified under all conditions. A relative density of higher than 99% was achieved with room temperature substrate, however, cracks along grain boundaries were observed in all samples. Significantly fewer cracks (< 0.5 %) were observed with specimens printed on a heated substrate. A correlation between process conditions and the formation of solidification cracks was established, and minimization of solidification cracking is discussed in terms of solidification fundamentals.
3:00 PM
Solidification Mechanisms during Selective Laser Melting of Binary Ni-Cu, Ni-Al and Ni-Zr Alloys: Clara Galera-Rueda1; María Teresa Pérez-Prado2; Javier Llorca1; 1IMDEA Materials Institute & Technical University of Madrid; 2IMDEA Materials Institute
Alloying additions play a critical role on the development of microstructures during selective laser melting (SLM). Most of the work on SLM has been carried out in multicomponent alloys and there is limited information about the influence of each alloying element on the solidification processes. Powders of pure Ni and three binary alloys (Ni-10%wt. Al, Ni-20%wt. Cu, and Ni-7%wt. Zr) were prepared by atomization to manufacture samples by SLM. It was found that the addition of Cu to Ni results in grain growth and texture strengthening; the addition of Al to Ni leads also to grain growth and to a change in the dominant texture component, which is related to the precipitation of Ni3Al. Finally, the intense segregation of Ni5Zr in Ni-Zr leads to a refined isotropic microstructure. The mechanisms responsible for this behavior are discussed and their influence on the nucleation of defects (pores, cracks) is analyzed.
3:20 PM
Solidification Microstructure in Invar-Cu Intrinsic Nanocomposites by Selective Laser Melting: Haobo Wang1; Prosenjit Biswas1; Ji Ma1; Jerrold Floro1; 1University of Virginia
This research ultimately aims to develop thermally stable, precision reflector optics made from Invar-Cu alloys by laser powder bed fusion. The goal is to manipulate the solidification microstructure to obtain an appropriate composite microstructure that simultaneously provides low thermal expansion (based on Invar) and good thermal conductivity (based on Cu). Ideally, we seek to achieve an oriented Invar cellular matrix with a percolating intercellular Cu network that acts as thermal conduction channels throughout the build volume. In the initial research phase, the relationship between the laser scan parameters and the microstructure was studied by writing single melt tracks on arc-melted Invar-Cu boules. The resultant solidification microstructure and composition were characterized throughout melt-pool cross-sections. The deleterious effects of keyholing will be discussed. Microstructures will subsequently be connected to simulated thermal histories (temperature gradient & interface velocity) to construct a processing diagram. Support by the II-VI Foundation is gratefully acknowledged.
3:40 PM Break
3:55 PM
The Effect of Solidification Pathway on Grain Boundary Fractality: Akane Wakai1; Amlan Das2; Atieh Moridi1; 1Cornell University; 2Cornell High Energy Synchrotron Source
Austenitic stainless steels 304L and 316L were additive manufactured under the same processing conditions to reveal two distinctive microstructures. The chemical composition, and more specifically the ratio of ferrite-stabilizing constituents to austenite-stabilizing constituents, determines the solidification pathway (ferrite-to-austenite solidification for 304L and primary austenite solidification for 316L). Despite the same processing conditions for both materials, the resulting grain morphology for 304L is particularly unique. There are three aspects to its complex microstructure: (1) the presence of hierarchical grain substructures; (2) there is a wide range of grain size spanning nearly two orders of magnitude; and (3) the grain boundaries are rough and convoluted, resembling a fractal object. The intermediate phase in 304L, ferrite, is responsible for the peculiar grain morphology. Operando X-ray diffraction studies at Cornell High Energy Synchrotron Source substantiate the solidification pathways. The findings from the study open a new avenue for grain boundary engineering using additive manufacturing.
4:15 PM
Layer-wise Optimization of Powder-bed Fusion Parameters Using Machine Learning Models in Metal Additive Manufacturing: Najmeh Samadiani1; Dayalan Gunasegaram1; 1Commonwealth Scientific and Industrial Research Organisation (CSIRO)
The ability to control the formation of defects and anomalies in metal parts during their building using powder bed fusion (PBF) additive manufacturing (AM) processes is a critical strength that can make these technologies more attractive to the industry. The required knowledge is presently generated through dozens of trial and error experiments; these inform the selection of the initial values of process parameters and their change during the build process. Machine learning (ML) models present an alternative to the time-consuming and expensive trial and error process. By analyzing vast amounts of data efficiently, they uncover critical relationships between process parameters that may be hidden from human analysis. Significantly, these models can be used for new parts that have not been made before. We discuss the various ML models that may help optimize process parameters to mitigate defects and anomalies in both laser-beam and electron-beam processes.
4:35 PM Cancelled
Microstructure and Hardness Evolutions of Stainless Steel 316L and Nimonic 90 Bimetallic Components along the Build Direction: Samia Razzaq1; Bosheng Dong2; Zengxi Pan2; Huijun Li2; Simon Ringer1; Xiaozhou Liao1; 1University of Sydney; 2University of Wollongong
Joining dissimilar materials using conventional welding and joining techniques could be challenging due to the formation of brittle intermetallic compounds during solidification, which deteriorates the mechanical properties at the bimetallic interface. Additive manufacturing is a promising technique to overcome this problem as additive manufacturing can alter the composition at the interface to prevent the formation of harmful intermetallic compounds during dissimilar metal joining. In this study, a structural component with stainless steel 316L and nimonic 90 dissimilar materials is manufactured using the wire arc additive manufacturing technique with the dissimilar metal interface parallel to the build direction. The microstructural evolution at the interface along the build direction is investigated using electron microscopy. Vickers hardness testing is conducted to explore the hardness along the build direction at the materials interface. The relationship between local microstructure and hardness is presented. This work is a part of MURI and AUSMURI collaborative research.
4:55 PM
Using Defects as ‘Fossil Records’ in Metallic Parts Produced with Electron Beam Powder Bed AM: Katie O'Donnell1; Amamchukwu Ilogebe1; Maria Quintana1; Peter Collins1; 1Iowa State University
Defects in additive manufacturing are typically considered to be deleterious features and the literature has focused on the intent of reducing or eliminating defects from final parts, either during the actual additive process or with post-processing methods. However, defects can serve as microstructural informants or ‘fossil records’, recording evidence of physical phenomena at play during additive manufacturing processes. Such records help fill knowledge gaps that still exist. Analysis of a variety of defects in electron beam melted Ti-6Al-4V, Inconel 738, and Haynes 282 parts using compositional, crystallographic, and microstructural characterization methods can reveal key information about timeline and cause-effect of formation of different types of defects, including lack-of-fusion defects, solute segregation and aluminum vaporization, nonmetallic inclusions, and columnar grain growth changes, among others. The effect of different scan strategies and geometries on the resulting defect formation and retention has been studied for these three alloys. MURI and AUSMURI Collaborative Research.
5:15 PM
Temporal Transients of Plastic Strain Partitioning between Alpha and Beta Phases in Ti6Al4V during Thermo-mechanical Gyrations: Sabina Kumar1; Kate Shanks2; Dieter Ishiem3; Sudarsanam Babu1; 1University of Tennessee Knoxville; 2FAST Beamline, CHESS; 3NUCAPT, Northwestern University
Spatial and temporal thermal gradients are expected to induce stresses above and below the yield stress of the phases, leading to plastic instabilities. Plastic straining at high temperatures is expected to change relative phase fractions and local constitutive properties. Although the role of thermal signatures can be rationalized based on nucleation and growth of the product/parent phase under non-isothermal conditions, all the above work have not considered the role of thermo-mechanical gyrations. The current work pertains to the history-dependent dynamic interactions of phase transformations and deformation characteristics. A time-resolved study of the partitioning and accumulation of plastic strains between the alpha and beta phases is studied with in-situ high energy X-ray experiments conducted at CHESS. Atom Probe analysis indicated changes in the concentration of Al and V across the interface. Results were evaluated with DICTRA to rationalize the thermodynamics equilibrium kinetics of the interface under complex thermo-mechanical reversals.