Additive Manufacturing: Advanced Characterization with Synchrotron, Neutron, and In Situ Laboratory-scale Techniques II: High-speed X-ray Diffraction
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Fan Zhang, National Institute of Standards and Technology; Donald Brown, Los Alamos National Laboratory; Chihpin Chuang, Argonne National Laboratory; Joy Gockel, Colorado School Of Mines; Sneha Prabha Narra, Carnegie Mellon University; Tao Sun, Northwestern University
Monday 8:30 AM
February 28, 2022
Room: 258A
Location: Anaheim Convention Center
Session Chair: Andrew Chuang, Argonne National Laboratory; Fan Zhang, National Institute of Standards and Technology
8:30 AM Introductory Comments
8:40 AM Invited
In Situ X-ray Diffraction and Visualization of Laser Melting and Subsequent Phase Evolution: Anthony Rollett1; 1Carnegie Mellon University
In situ x-ray experiments at modern light sources have provided many insights into materials aspects of laser-based additive manufacturing. Visualization of the melting process has demonstrated the importance of metal vaporization for, e.g., driving keyhole development, porosity formation, spatter, hot cracking and absorptivity. Related to the scientific impact has been the importance of the new understanding on process control: the laser light intensity is directly related to spot size, which then controls the intensity of keyholing. Absorptivity directly influences the extent of melting, which in turn affects melt pool overlap and whether or not lack of fusion porosity occurs. Post-solidification, in situ diffraction experiments reveal phase evolution. Stainless steel (316) is found to solidify as ferrite before transforming (partially) to austenite [CHECK J’s paper]. Alloy 718 precipitates carbides and Laves phase but not other commonly observed phases. At high enough cooling rates, Ti-6Al-4V transforms martensitically.
9:10 AM
Study of Solidification Behavior in Laser Additive Manufacturing Using Synchrotron X-ray Diffraction: Adrita Dass1; Atieh Moridi1; 1Cornell University
Understanding the dynamic solidification behavior during metal additive manufacturing (AM) is essential as it directly influences final microstructures, defects and therefore mechanical properties of the part. Novel in-operando x-ray experiments at different spatial and temporal resolutions provide an unprecedented opportunity to develop a new understanding of the underlying physics of the AM process and solidification in cooling rates applicable to beam-based AM. Here we demonstrate a novel approach using synchrotron x-ray diffraction to link the ‘mushy zone’ during solidification and solidification parameters for Inconel 625. Using this approach, we calculate the melt pool and mushy zone dimensions, along with real-time thermal gradient, cooling rate and solidification front velocity, all by virtue of tracking real-time changes in lattice parameters. We also estimate the dendritic arm spacings and the grain structure expected in the part. Results are corroborated with microscopy analysis of the printed structures.
9:30 AM Invited
NOW ON-DEMAND ONLY - Unveiling Phase Transformation Dynamics of Metals under Additive Manufacturing Conditions by In-situ High-speed X-ray Diffraction: Lianyi Chen1; 1University of Wisconsin-Madison
The lack of understanding of the phase transformation dynamics of metals under additive manufacturing conditions is currently a bottleneck for establishing the relationships between processing condition and microstructure in fusion-based additive manufacturing of metals. Here, I will present our research on revealing phase transformation dynamics during laser melting by in-situ high-speed, high-energy synchrotron x-ray diffraction, with a focus on a precipitation hardening martensite stainless steel, 17-4 PH. We revealed the phase evolution (types of phases, relative fraction of phases) as a function of time in 17-4 PH during laser melting, which helped us to understand the complex microstructures observed in the as-printed 17-4 PH. I will also discuss the design of a 17-4 PH alloy, guided by the revealed phase transformation dynamics, to achieve desired fully martensitic structure across a wide range of cooling rates for additive manufacturing.
10:00 AM Break
10:15 AM Cancelled
Application of High-speed X-ray Diffraction to Understand the Microstructure Evolution during Additive Manufacturing of Hot-work Tool Steels: Greta Lindwall1; Niklas Holländer Pettersson1; Hans-Henrik König1; A. Durga1; Chrysoula Ioannidou1; Fan Zhang2; Andrew Chihpin Chuang3; Qilin Guo4; Lianyi Chen4; Steven Van Petegem5; 1KTH Royal Institute of Technology; 2NIST; 3Argonne National Laboratory; 4University of Wisconsin; 5Paul Scherrer Institut
Laser-Powder Bed Fusion (L-PBF) enables manufacturing of complex tool geometries with improved tool performance. This has increased the interest in developing printable medium-carbon martensitic steels aimed for hot-work tooling application where the incorporation of conformal cooling channels in the tool design may prolong the tool life. A challenge for the development of these new tool steels for L-PBF is to understand their cracking susceptibility and its relation to the complex microstructure with martensite and a network of retained austenite that develops during processing. In this work, we show how we utilize high-speed X-ray diffraction methods to understand the response of tool steels under realistic L-PBF processing conditions enabled by the use of sample environments developed at SLS, PSI and APS. Focus is on the solidification behavior and austenite to martensite transformation, and how we use the acquired data for development and validation of Calphad-based models aimed for computational materials design.
10:45 AM
In-situ Temperature Quantification during Laser Powder Bed Fusion Additive Manufacturing: Rachel Lim1; Tuhin Mukherjee1; Tarasankar DebRoy1; Thien Phan2; Darren Pagan1; 1Pennsylvania State University; 2National Institute of Standards and Technology
Laser powder bed fusion additive manufacturing produces rapid changes and large gradients in temperature which in turn influence microstructural development in the material. Qualification and model validation of the process itself and resulting material produced necessitates the ability to characterize these bulk temperature fields. However, there are no proven means to directly probe material temperature in the bulk of an alloy (as opposed to the surface) while it is being processed. To address this gap in characterization capabilities, a novel means is presented to accurately extract bulk temperature metrics from in-situ synchrotron x-ray diffraction measurements to provide quantitative analysis of temperature evolution during laser powder bed fusion. Temperature metrics are determined using a supervised machine learning surrogate model trained with a combination of thermal modeling and x-ray diffraction simulation.
11:05 AM
Investigating the Ferrite-to-Austenite Solidification Competition in Stainless Steel Laser Welds with Time-resolved X-ray Diffraction: Joseph Aroh1; Seunghee Oh1; Rachel Lim2; Benjamin Gould3; Andrew Chuang3; P. Chris Pistorius1; Anthony Rollett1; 1Carnegie Mellon University; 2Pennsylvania State University; 3Argonne National Laboratory
It is generally accepted that high solidification rates result in a shift from primary ferrite to primary austenite solidification mode in stainless steels with low Cr/Ni equivalency ratios based on differences in dendrite tip growth kinetics between the two phases. This understanding was tested with high-speed synchrotron x-ray diffraction measurements during in situ laser melting and re-solidification of various stainless steels. A large-area detector was employed to capture complete Debye-Scherrer rings at a high spatiotemporal resolution allowing laser scan velocities to range from 0.01 – 0.5 m/s. The time-resolved diffraction patterns were correlated with ex situ microstructural characterization of the sectioned melt tracks to understand how the solidification sequence results in the final microstructure. This analysis is the first to directly link the in situ characterization of liquid-solid phase transformation kinetics with the various solidification microstructures that occur in laser welds as a function of both solidification rate and composition.
11:25 AM
Time-resolved Structural Characterization of Ni Alloy 718 under Laser Processing with In-situ Synchrotron X-ray Diffraction: Seunghee Oh1; Rachel Lim2; Joseph Aroh1; Benjamin Gould3; Andrew Chuang3; Robert Suter1; Anthony Rollett1; 1Carnegie Mellon University; 2Penn State University; 3Argonne National Laboratory
Laser melting is key for various additive manufacturing applications because of its superior power, speed, and process resolution. It induces strong temperature gradients, which cause rapid and unique phase evolution not measurable by traditional instruments. To study this in Ni alloy 718, we performed in-situ X-ray diffraction measurements using high-energy synchrotron x-rays and a high-speed large-area detector. The spatially and temporally resolved observation allows us to examine the microstructures and lattice parameters in resolidified and heat-affected alloy 718. The collected diffraction patterns demonstrate transient changes in phase and structure parameters of the lattices. Combined with microscopy, the deformation can be identified and quantified, which presents the most frequent deformation occurring in the lattices oriented to parallel and vertical to the laser scan direction. Additionally, the results indicate that the anisotropicity of the lattices in FCC contributes to not only the evolution in the lattice parameters but also the deformation behavior.