Additive Manufacturing of Metals: Applications of Solidification Fundamentals: In-situ Monitoring and Sensing
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
Wednesday 8:30 AM
March 22, 2023
Room: 21
Location: SDCC
Session Chair: Lianyi Chen, University of Wisconsin-Madison; Wenda Tan, University of Michigan
8:30 AM
Rapid Characterization of Solidification Phase Transition of Additive Aluminum Alloy: Fan Zhang1; Andrew Iams1; Feng Yi1; David LaVan1; Jordan Weaver1; Brandon Lane1; Qilin Guo2; Jiandong Yuan2; Lianyi Chen2; Andrew Chuang3; Darby LaPlant4; John Martin4; 1National Institute of Standards and Technology; 2University of Wisconsin, Madison; 3Argonne National Laboratory; 4HRL Laboratory
Metal-based additive manufacturing (AM) is among the most heavily pursued advanced manufacturing technologies worldwide. Reliable data that capture the transient microstructural transformations during an AM build remain scarce, primarily due to challenges associated with rapid nonequilibrium phase transformations at extreme cooling and heating rates (up to 10^6 K/s) and repeated thermal cycling in a layer-by-layer fabrication. We performed in situ, high-speed thermal and synchrotron-based diffraction measurements on an advanced, commercially available AM aluminum alloy to provide direct and quantifiable data of the phase transitions under various AM build conditions. Our high-resolution ex-situ electron microscope measurements complemented the in situ measurements. They enabled us to understand the solidification pathway in some of the best-performing AM aluminum alloys with a bimodal grain microstructure. Our measurements also provide high-fidelity thermodynamics data for alloy design and accelerate AM aluminum and other commercially important alloys.
8:50 AM
Pore Dynamics and Formation Mechanisms during Directed Energy Deposition Additive Manufacturing: Kai Zhang1; Yunhui Chen1; Xianqiang Fan1; Sebastian Marussi1; Imogen Cowley1; Maureen Fitzpatrick2; Shishira Bhagavath1; Martyn Jones3; Chu Lun Alex Leung1; Peter Lee1; 1University College London; 2European Synchrotron Radiation Facility; 3Rolls Royce plc.
Directed energy deposition (DED) is a promising laser additive manufacturing technique to build large components and for repair applications. Porosity can limit the industrialisation of the DED process, detrimental to the mechanical performance of manufactured components. In this study, we utilised high-speed in situ synchrotron X-ray imaging to observe the pore dynamics and pore formation mechanisms. We revealed three pore behaviors and their formation mechanisms: (i) large pores are formed by pore coalescence; (ii) pores are being pushed in the melt pool by the Marangoni flow, while large pores escape periodically once they reach a critical pore size; (iii) the majority of the pores form from melting of gas atomized powders rather than previously built layers. The pore dynamics and formation mechanisms discovered here can guide to develop porosity elimination strategy in industrial practice.
9:10 AM
In-situ X-ray Characterization for Additive Manufacturing of Inoculants-treated Aluminum Alloy: Sen Liu1; Vivek Thampy2; Peiyu Quan1; Christopher Tassone2; 1Stanford University; 2SLAC National Accelerator Laboratory
Additive manufacturing of densified and defect-free Aluminum (Al) alloy faces many challenges because of its low laser absorption, high thermal conductivity, and fast cooling rate; most Al alloys are defined as highly crack sensitive with poor printability. Inoculation treatment offers a chance to solve this problem, where the inoculants are mixed into molten metals and act as heterogeneous nucleation catalysts during solidification. Equiaxed grains accommodate the solidification shrinkage allowing the production of defect-free samples. For the first time, this work will present the results of in-situ X-ray diffraction and imaging of inoculants-refined and unrefined Al6061 alloy printing at Stanford synchrotron radiation lightsource. The high-speed X-ray diffraction extracts subsurface phase transition and cooling rates from melted to solidified track. The X-ray radiography reveals the pore formation and fluid dynamics mechanism during laser melting. The effects of processing parameters and constituted composition on the phase transition and molten pool characteristics are analyzed.
9:30 AM
In-situ/Ex-situ Visualization of Microstructure Evolution in Aluminum Alloys under Additive Manufacturing Conditions: Oliver Hesmondhalgh1; Alec Saville1; Brian Rodgers1; Adriana Eres Castellanos1; Joseph McKeown2; Kester Clarke1; Alain Karma3; Amy Clarke1; 1Colorado School of Mines; 2Lawrence Livermore National Laboratory; 3Northeastern University
Additive manufacturing (AM) is highly customizable and can be used for the production of complex structures. But, 3D printed metals often contain microstructural features like coarse columnar grains that may result in anisotropic properties or metastable phases. Rapid solidification has been found to produce characteristic microstructures and metastable phases in aluminum-germanium (Al-Ge) alloys. With recent experimental advances in advanced and in-situ characterization, the visualization of solidification dynamics in metals and alloys at unprecedented length- and timescales is now possible. This work presents the in-situ characterization of microstructural evolution in Al-Ge alloys by dynamic transmission electron microscopy (DTEM). Complementary ex-situ characterization was also performed. The formation of metastable phases in Al-Ge alloys is found to be highly dependent upon the solidification conditions and local solutal conditions in the melt pool. These results provide new insights into phase stability and microstructure development with processing variations during additive manufacturing.
9:50 AM Break
10:05 AM Invited
Phase Transformation Dynamics in Laser Additive Manufacturing of Metals: Lianghua Xiong1; Wenjun Liu2; Yang Ren3; Peter Kenesei2; Chris Benmore2; John Low2; Anping Dong1; Baode Sun1; Andrew Chuang2; 1Shanghai Jiao Tong University; 2Argonne National Laboratory; 3City University of Hong Kong
Phase transformation and resultant phase structure are essential for engineered property and performance of additively manufactured metallic components. However, rapid solidification occurring in laser additive manufacturing typically renders phase transformation far from equilibrium and inevitably challenges the prediction of complex phase structure and selection of favored phases. Here, we report phase transformation dynamics of melt pool revealed by synchrotron in-situ experiments and ab initio molecular dynamics simulation. The physics of atomic structure transition and consequent processing-structure-property relationship will be discussed. The discovery of phase transformation dynamics deepens fundamental understanding of phase structure control in the rapid solidification process of laser assisted manufacturing and formulates novel insights for alloy design of metal 3D printing.
10:25 AM
Operando Synchrotron X-ray Diffraction Reveals Stages of Directional Solidification in Additive Manufacturing: Adrita Dass1; Chenxi Tian1; Darren Pagan2; Atieh Moridi1; 1Cornell University; 2Pennsylvania State University
Directional solidification is predominantly observed in additive manufacturing (AM) of Inconel 625 and is primarily dendritic, exhibiting distinct stages including: crystallite formation; bending and rotation; fragmentation and assimilation, intra- and inter-growth; and formation of secondary phases. Previously, synchrotron imaging has been used to study these phenomena, focusing on slower time scales and lighter Al- and Ti-based alloys that provide sufficient phase contrast. However, complete examination of these processes during metal AM has not been undertaken due to challenges of achieving sufficient temporal resolution and phase contrast due to fast solidification dynamics. Instead, our approach of using synchrotron x-ray diffraction alleviates some of these challenges and enables new understanding of the solidification dynamics during AM. Specifically, thermo-mechanical and microstructural information such as the evolution of lattice strain and crystallographic texture, not possible with other techniques, are measured in situ. Electron microscopy supports conclusions derived from the phenomena observed in situ.
10:45 AM
Automatic Melt Pool Segmentation and Tracking in the X-ray Image Sequence: Maede Maftouni1; Bo Shen1; Andrew Law1; Rongxuan Wang1; Zhenyu Kong1; 1Virginia Tech
The melt pool is the region of the superheated melted metal generated by laser irradiation on the powder bed surface, whose shape and evolution monitoring plays a critical role in unveiling the manufactured part's microstructural characteristics. Yet, melt pool boundary detection from in-situ X-ray images is challenged by the high noise level, brightness fluctuations, and lack of a sharp image boundary between the melted and unmelted hot metal regions. Here, we present a novel and robust-to-noise computer vision model that automates the melt pool segmentation and tracking in the X-ray image sequences to facilitate the melting process inspection and laser parameter calibration. This work is the first to use the video object segmentation deep learning methodology for melt pool segmentation, with an improved melt pool detection performance over the baseline edge detection techniques.
11:05 AM
Solidification Modes during Additive Manufacturing Thermal Conditions Revealed by High-speed X-ray Diffraction: Hans-Henrik Konig1; Niklas Holländer Pettersson1; A Durga1; Steven Van Petegem2; Daniel Grolimund2; Andrew Chihpin Chuang3; Qilin Guo4; Lianyi Chen4; Christos Oikonomou5; Fan Zhang5; Greta Lindwall1; 1KTH Royal Institute of Technology; 2Paul Scherrer Institute; 3Argonne National Laboratory; 4University of Wisconsin-Madison; 5Uddeholm AB
Laser-Powder Bed Fusion (L-PBF) enables manufacturing of complex tool geometries with improved tool performance. During L-PBF high thermal gradients and high solidification velocities occur and determine the solidification mode. To study the impact of the thermal gradients and solidification velocities on the solidification mode in a hot-work tool steel, we used two synchrotron-based, high-speed X-ray diffraction setups. Primary δ-ferrite is observed at a cooling rate of 2.12 × 104 K/s, and at a higher cooling rate of 1.5 × 106 K/s, δ-ferrite is suppressed, and primary austenite is observed. The thermal conditions during the experiments are linked to a solidification model, that is based on the dendrite growth model by Kurz-Giovanola-Trivedi (KGT). The modelling results predict the experimental observations. This work shows how in-situ XRD measurements can be applied to understand the microstructure evolution and to validate computational thermodynamics and kinetics models, facilitating alloy and parameter development for AM processes.
11:25 AM
Operando Tomography during Laser-based Powder Bed Fusion - Towards 4D Imaging of Melt Pool Dynamics: Malgorzata Makowska1; 1Paul Scherrer Institut
Optimization of the properties of Laser Powder Bed Fusion (LPBF) -manufactured ceramic parts requires an insight into formation mechanisms of structural defects. The results of the first operando tomographic microscopy during LPBF of ceramics, using an in-house built LPBF setup at the Tomcat beamline of SLS (Paul Scherrer Institute) will be presented. The 3D imaging experiments were performed using a high speed tomography setup and a miniaturized LBPF machine allowing for the laser scanning during high-speed rotation of the sample stage. Time-resolved 3D imaging with acquisition rate of 100 tomograms per second provided direct insight into the phenomena not accessible in 3D with other techniques, in particular, the melt pool dynamics, crack and porosity formation mechanisms. The achieved information provides understanding of underlying processes, but is also crucial for the development and verification of models used for the LPBF process simulations, which can be extended to other materials.