Additive Manufacturing Benchmarks 2022 (AM-Bench 2022): Materials I: Phase Evolution
Program Organizers: Brandon Lane, National Institute of Standards and Technology; Lyle Levine, National Institute of Standards and Technology
Monday 1:30 PM
August 15, 2022
Room: Regency Ballroom III & IV
Location: Hyatt Regency Bethesda
Session Chair: Anthony Rollett, Carnegie Mellon University
1:30 PM Invited
Predicting Material Behavior with Improved Solidification Models for the AM Process Window: Adam Hope1; Kaisheng Wu1; Jan Julin2; Johan Jeppsson2; Paul Mason1; 1Thermo-Calc Software Inc; 2Thermo-Calc Software AB
Predicting localized material properties in additive manufacturing relies on linking chemistry and processing conditions to microstructure in ICME frameworks. In earlier work, using CALPHAD thermodynamics and the Scheil Gulliver equation to generate composition and temperature dependent data for latent heat and heat capacity has been shown to improve the accuracy of finite element simulations to predict the size, shape, and temperature of the laser melt pool. However, rapid solidification, typical of AM processes, can lead to solute trapping, where solute may be incorporated into the solid phase at a concentration significantly different from that predicted by equilibrium thermodynamics. To account for this effect, solute trapping models by Aziz and Kaplan have been incorporated into the CALPHAD/Scheil methodology. A case study is presented to show how this can lead to better microstructure prediction in Alloy 718 and the effect of solute trapping on thermophysical properties to improve finite element modeling.
2:00 PM Invited
Stable Nitride Precipitation in Additively Manufactured Nickel Superalloys: James Zuback1; 1National Institute of Standards and Technology
With negligible quantities of nitrogen, wrought and welded solid solution strengthened nickel superalloys usually contain carbides and topologically close-packed phases. However, appreciable nitrogen levels, along with alloy chemistry, can drive the precipitation of a range of unanticipated nitrides in additively manufactured Inconel 625. Metal nitrides (MN), Z-phase (CrNbN), and η-nitrides (M6N) were characterized in Inconel 625 containing relatively low Fe and Ti, and high Si. Conversely, only MN nitrides existed in a similar Inconel 625 alloy with elevated mass fractions of Ti and Fe. These various phases were not fully predicted using state-of-the-art computational thermodynamic tools and databases, indicating a sparsity of data for nickel superalloys. Even after hot isostatic pressing, many nitrides persisted and only experienced slight changes in composition and lattice parameters in both materials. The stability of these nitrides presents a potential pathway for achieving enhanced high temperature and creep properties within this and similar alloy systems.
2:30 PM Invited
Role of Composition in High Temperature Heat-treatment Response of Additively Manufactured 17-4 PH Stainless Steel: Derek Shaffer1; Todd Palmer1; 1Pennsylvania State University
Precipitation hardening (PH) stainless steels processed using additive manufacturing (AM) display variations in heat treatment responses and mechanical properties. These variations have been primarily attributed to changes in interstitial element compositions within the allowable ranges. With AM processing of these alloys, composition variations of both interstitial and primary alloying elements combined with microstructures that differ from wrought, impact the thermodynamic stability of important phases such as copper, austenite, delta-ferrite, nitrides, and oxides. This work aims to connect compositional changes in interstitial alloying elements like nitrogen and oxygen as well as other primary elements in AM PH stainless steels to microstructures after hot isostatic pressing (HIP) and solution heat-treatments. A predictable, high temperature heat-treatment response can be established by investigating key aspects of solutionizing and HIP such as the thermodynamic stability of delta-ferrite and copper as well as the influence high temperature phases like nitrides and oxides.
3:00 PM Break