Additive Manufacturing of Metals: Applications of Solidification Fundamentals: Solidification Structure and Defects
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Solidification Committee
Program Organizers: Alex Plotkowski, Oak Ridge National Laboratory; Lang Yuan, University of South Carolina; Kevin Chaput, Northrop Grumman; Mohsen Asle Zaeem, Colorado School of Mines; Wenda Tan, The University of Michigan; Lianyi Chen, University of Wisconsin-Madison
Tuesday 2:00 PM
March 16, 2021
Room: RM 4
Location: TMS2021 Virtual
2:00 PM
A Phase-field Study of Epitaxial Effect on Solidification Microstructure in Metal Additive Manufacturing: Jiwon Park1; Joo-Hee Kang1; Chang-Seok Oh1; 1Korea Institute of Materials Science
In this work, the epitaxial effect on the microstructure evolution under rapid solidification condition of additively manufactured AlSi10Mg alloy was investigated with phase-field simulation and electron backscatter diffraction analysis (EBSD). In order to perform the quantitative modeling, phase-field simulations were set from the crystallographic information observed in EBSD and directly compared to the orientation maps. Phase-field simulation successfully demonstrated the microstructural evolution when the appropriate interface anisotropy model is chosen in 3-dimensional simulation. The resulting microstructure was primarily determined by the local thermal gradient and cooling rates. Due to the epitaxial effect from partially melted, previously deposited layer, kinked grain structure across several melt-pool boundaries were observed along the building direction.
2:20 PM
Composition and Equilibrium Phase Diagram Feature Effects on the Printability of Alloys: Raiyan Seede1; Xueqin Huang1; Bing Zhang1; Austin Whitt1; Alaa Elwany1; Raymouno Arroyave1; Ibrahim Karaman1; 1Texas A&M University
Additive manufacturing (AM) has gained considerable academic and industrial interest due to its ability to produce parts with complex geometries with the potential for local microstructural control. However, due to the complexity and inadequacy in current knowledge of solidification processes, optimization of materials and process parameters for AM is an arduous task. This work sheds light on the effects of alloying composition and equilibrium phase diagram features on the solidification microstructures in four binary nickel-based alloys. These alloys are selected to quantify the effects of varying solidification temperature ranges, thermophysical properties, and solidification conditions on resultant microstructures in single tracks and bulk parts. A processing map is constructed for each of these alloys in order to determine how their material properties affect the printability of the alloys. This knowledge will be vital in optimizing alloy chemistry and process parameters for the complex solidification mechanisms in AM processes.
2:40 PM
Influence of Process Parameters on the Microstructure Evolution and Mechanical Properties of Additively Manufactured 316L Stainless Steel: Ankur Kumar Agrawal1; Dan Thoma1; 1University of Wisconsin Madison
In SLM techniques, processing parameters like laser power and scanning speed affects the spatial and temporal solidification condition (cooling rate and thermal gradient) and melt pool geometry. The aim of the work is to investigate and build a coherent relationship between the processing parameters and as-fabricated microstructural features. High-throughput experimentation on hundreds of specimens was carried out to rapidly identify a processing window. Within the processing window, microstructural investigation at different length scales (i.e., grains size and morphology, texture, primary dendrite arm spacing, and melt pool geometry analysis) were analyzed on different specimens. Finer grain size and dendritic spacing, more random texture, and shallower melt pool was obtained at lower energy density values. A model is proposed to explain the dependence of microstructure on the melt pool geometry and the solidification conditions. Finally, mechanical properties to these specimens were evaluated using the hardness and compression test.
3:00 PM
LPBF Processing of the Al-Ni Eutectic Alloy: Experiments and Phase Field Simulations: Guillaume Boussinot1; Markus Apel1; Markus Döring2; 1Access e.V.; 2LPT University Erlangen
We study experimentally and using phase field simulations the Laser Powder Bed Fusion (LPBF) processing of the eutectic Al-Ni alloy. Varying the alloy composition, we investigate the mechanisms leading to a coupled two-phases eutectic solidification or to a single phase solidification. While at low cooling rates the eutectic solidification has been the subject of an extensive work since the 90's, we find new phenomena arising at the large cooling rates that are typical for additive manufacturing and especially for LPBF. These new phenomena are, in line with the strongly out-of-equilibrium regime identified in our previous publication [Phys. Rev. Applied 11, 014025 (2019)], the expression of a eutectic Peclet number (eutectic spacing over diffusion length) and of a dendritic Peclet number (tip radius over diffusion length) of order unity.
3:20 PM
Modeling Grain Refinement for Metallic Additive Manufacturing: Yijia Gu1; 1Missouri University of Science and Technology
Experimentally, it has been demonstrated that grain refinement is one of the most effective ways to improve manufacturability for metallic additive manufacturing (AM). However, the grain refining mechanism of AM is still largely unknown. Many fundamental questions remain to be addressed. In this work, we will employ a phase-field model and the free growth model to investigate the grain refinement for AM. Realistic solutal and thermal diffusion are coupled into the phase-field model. We will discuss the fundamentals aspects, such as the effect of dissipation of latent heat, size and distribution of inoculant particles, interface velocity, solute trapping, and cooling rate on the grain refinement during AM process. Our results will shed light on the precise control of grain structures and the designing of effective grain refiners for AM.
3:40 PM
New Composition Based Index for Solidification Cracking Resistance: Rafael Giorjao1; Benjamin Sutton1; Antonio Ramirez1; 1The Ohio State University
Defects such as solidification cracking are commonly observed in metal-based additive manufacturing processes, which critically affect their mechanical and physical properties. Computational modeling has emerged as a useful tool to assist with the exploration of solidification cracking behavior. However, the application of such tools is often limited by model complexity/availability of material-specific input parameters. Regarding this issue and the demanding need for reliable models, a simple model to explore solidification cracking resistance of alloys during additive manufacturing is presented. The presented model evaluates interdedritic liquid flow during non-equilibrium solidification, which plays a substantial role in solidification cracking resistance. The dendritic profiles were built using calculated fractions of solid from commercial thermodynamic software for different compositions. The calculated results were compared to experimental solidification cracking data and showed satisfactory agreement. It is envisaged that this new approach can aid in the design and development of alloys, specifically for additive manufacturing applications.
4:00 PM Cancelled
Phase-Field Modeling of CET During Alloy Solidification: An Insight for Additive Manufacturing: Nima Najafizadeh1; Yijia Gu1; 1University of Missouri Science and Technology
The development of grain structures during solidification is critical for several material properties. Recently, it was demonstrated that small equiaxed grains can effectively resist cracking during additive manufacturing (AM), which can potentially unlock the alloy selection limit for AM technology. In this work, a phase-field model with solute trapping will be developed to study the grain structure formation for AM. The thermal gradient, cooling rate, and size and distribution of inoculant particles will be considered. Taking inoculated aluminum alloy as an example, the columnar-to-equiaxed transition (CET) will be systematically investigated using the developed phase-field model. The results will shed light on the alloy design and microstructure control for AM.
4:20 PM
Quantifying the Influence of Local Layer Thickness on Pore Evolution during Laser Powder Fusion Using High-speed X-ray Imaging: Chu Lun Alex Leung1; Yuze Huang1; Samuel J. Clark1; Yunhui Chen1; Sebastian Marussi1; Lorna Sinclair1; Iain Todd2; Margie P. Olbinado3; Elodie Boller4; Alexander Rack4; Peter D. Lee1; 1University College London; 2University of Sheffield; 3Paul Scherrer Institute; 4European Synchrotron Radiation Facility
Laser powder bed fusion additive manufacturing (LPBF) produces complex net-shape parts from alloy powders, in a layer-by-layer manner. Synchrotron X-ray imaging studies of pore evolution to date have mostly been in single-layer tracks on substrates, missing key interactions between the laser beam and pre-existing pores and other features in prior tracks. Here, we used an in situ and operando process replicator (ISOPR) and X-ray imaging to monitor the process dynamics during a multilayer build. We quantify the changes in keyhole geometry, porosity, and remelting zone, as a function of time, layer number, and local layer thickness. Our results demonstrate that the local layer thickness strongly influences surface topology, altering remelting, and pore evolution mechanisms. We use the extracted information to build a novel physical model accounting for the effect of layer-based thickness on heat transfer mechanisms, elucidating its impact on pore formation during multilayer LPBF additive manufacturing.