Materials Design and Processing Optimization for Advanced Manufacturing: From Fundamentals to Application: Materials Design and Processing Optimization: Session VII
Sponsored by: TMS Structural Materials Division, TMS: Alloy Phases Committee
Program Organizers: Wei Xiong, University of Pittsburgh; Dana Frankel; Gregory Olson, Massachusetts Institute of Technology

Thursday 8:30 AM
March 3, 2022
Room: 253B
Location: Anaheim Convention Center

Session Chair: Victoria Miller, University of Florida; Yan Li, Dartmouth College

8:30 AM  Invited
Role of Interstitial and Minor Alloying Element Additions on Microstructural Evolution in Additively Manufactured Materials: Todd Palmer1; 1Pennsylvania State University
    Metal powders are the primary feedstock for fusion-based and solid state additive manufacturing processes and are prone to the pick-up of interstitial and minor alloying elements. While the primary alloying elements typically fall within acceptable ranges, minor alloying elements, such as nitrogen and oxygen, are typically not monitored. These elements impact the phases formed and microstructural evolution in a range of stainless steels and nickel base alloys in both the as-deposited and post-processed conditions. High oxygen levels in stainless steels lead to the formation of oxygen-rich inclusions originating in the powder and impacting microstructural formation, mechanical properties, and corrosion behavior in additively manufactured materials. In solid solution strengthened nickel base alloys, high nitrogen levels drive the formation of nitride-based phases in the as deposited condition and persist through post-processing. These phases differ from those expected based in wrought materials and drive significant changes in the microstructural evolution and resulting properties.

8:55 AM  
Solidification Behavior of Additively Manufactured Martensitic Precipitation-hardenable Stainless Steels: Melanie Buziak1; Eric Lass1; 1University of Tennessee Knoxville
    The solidification conditions found during additive manufacturing (AM) of metallic alloys leads to compositional heterogeneity, non-equilibrium phase formation, and disparate microstructure that produces material properties unlike those of their wrought counterparts. This is particularly apparent in martensitic precipitation-hardenable stainless steels (PH-SS), where small variations in solidification conditions leads to changes in primary solidification phase (austenite or δ-ferrite), a transition from columnar to equiaxed grain morphology, and different solid-state transformations caused by the variable material composition and cyclic heating/cooling cycles of AM. This work aims to understand the mechanisms of the solidification behavior of laser-powder-bed-fusion (L-PBF) PH-SS through the investigation of powder feedstock chemistry and manipulation of processing parameters. Laser energy density and normalized enthalpy have been found to have an effect on the as-built microstructure and properties. The role of processing parameters on the solidification behavior is explored to gain greater control of the processing-structure-properties relationship of martensitic PH-SS.

9:15 AM  
Healing Damage in Friction Stir Processed Mg2Si Reinforced Al Alloy: Mariia Arseenko1; Florent Hannard1; Lipeng Ding2; Ankush Kashiwar1; Elie Paccou3; Lv Zhao4; Grzegorz Pyka1; Hosni Idrissi1; Williams Lefebvre3; Julie Villanova5; Eric Maire6; Julie Gheysen1; Aude Simar1; 1Universite Catholique De Louvain; 2Nanjing Tech University; 3Université de Rouen; 4Huazhong University of Science and Technology; 5ESRF; 6INSA Lyon
    During service life of Al alloys, damage occurs due to the presence of large intermetallic particles. Damage healing is a new paradigm to extend materials lifetime. In the present work, a new class of healable Al-0.5Mg2Si alloy is produced by Friction Stir Processing (FSP). In-situ tensile Scanning Electron Microscopy (SEM) tests have shown that sacrificial healable particles change damage mechanism by breaking first, while Fe-rich intermetallics are mostly remaining intact. The pre-damaged samples produced by a micro-tensile machine were further investigated by in-situ heating TEM including EDX analysis and automatic crystallographic orientation in TEM as well as atom probe tomography (APT) in order to track healing evolution of damaged particles and reveal healing mechanism. In situ X-Ray nano holotomography experiment carried out at ESRF with a pixel size of 35 nm provided additional statistical data on the healing ability of the bulk material after heating for various times at 400°C.

9:35 AM  
Material Flow Behavior Prediction of Additive Friction Stir Deposition Using Smoothed Particle Hydrodynamics: George Stubblefield1; Kirk Fraser2; Thomas Robinson3; Ning Zhu3; Ryan Kinser3; James Tew3; Bret Cordle3; James Jordon3; Paul Allison3; 1The Engineer Research and Development Center; 2National Research Council Canada; 3The University of Alabama
    In this study, particle tracking in smoothed particle hydrodynamics (SPH) simulations of additive friction stir depositions (AFS-D) were conducted in-order to elucidate deposition mechanics. The SPH model was validated using experimental depositions of two feedstock varieties, including anodized AA6061-T6 feedstock and AA6061-T6 copper wire core feedstock, to represent flow behavior from different regions of the feedstock. The experimental results revealed that the anodized oxides on the outside of the feedstock flowed to the retreating side, whereas the copper wire in the center of the feedstock migrated to the advancing side. Particle tracking results from the SPH simulations showed that, in general, particle movement is limited to directly beneath the feedstock. The rotational, radial, and traverse flow interactions visualized by AFS-D simulations explained the advancing and retreating side biases experienced by the internal copper wire and surface oxides on the anodized feedstock.