High Performance Steels: Modeling and Computation in Steels Research
Sponsored by: TMS Structural Materials Division, TMS: Steels Committee
Program Organizers: Ana Araujo, Vesuvius USA; C. Tasan, Massachusetts Institute of Technology; Jonah Kleem-Toole, Colorado School of Mines; Louis Hector, General Motors Global Technical Center; Tilmann Hickel, Bam Federal Institute For Materials Research And Testing; Benjamin Adam, Oregon State University

Wednesday 8:30 AM
March 2, 2022
Room: 252C
Location: Anaheim Convention Center

Session Chair: Allie Glover, Los Alamos National Laboratory; Chris Finfrock, Colorado School of Mines

8:30 AM
First Principles Calculations of Structural Point-defect Calculations in Austenitic Stainless Steels: Edwin Antillon¹; Noam Bernstein¹; Michelle Johannes¹; ¹Naval Research Laboratory
    We present first principles density functional theory calculations of atomic properties relevant to material strength of paramagnetic austenitic steel alloys. While paramagnetism manifests itself as a macroscopically non-magnetic phenomenon, significant deviation from experiment can result when calculating properties using nonmagnetic calculations. In this work we calculate elastic and point-defect properties using a magnetic sampling method via spin-polarized density functional theory to approximate the paramagnetic state by averaging over several static disordered magnetic configurations. The calculated values are used to evaluate parameters relevant to solid-solution strengthening and vacancy mediated diffusivity in 316 alloys or similar steel alloys.

8:55 AM
ICME Design of β-NiAl + Cu + VC Triple Nano-precipitate Strengthened Austenitic Steel: Colin Stewart¹; Paul Lambert²; Richard Fonda¹; Keith Knipling¹; Patrick Callahan¹; ¹US Naval Research Laboratory; ²US Naval Surface Warfare Center, Carderock Division
    A novel series of precipitate-strengthened FCC Austenitic steels stabilized by Mn additions has been developed via an integrated computational materials engineering (ICME) approach, achieving impressive hardness values over 500 HV, for an estimated yield strength of ~170 KSI. Investigation of this system has identified three nano-scale phases upon ageing, without prior rolling steps: (i) insoluble Cu (FCC) particles; (ii) ordered intermetallic β-NiAl (B2) precipitates; and small amounts of (iii) M₂₃C₆. Additional compositional modifications guided by ICME have been undertaken to stabilize nano-scale VC particles at a higher phase fraction, and in place of, M₂₃C₆. These VC particles have enabled an expanded range of age hardening heat treatments, as well as multiple possible interactions between β-NiAl + Cu + VC phases in this new alloy. The ability to tailor precipitate interactions though multi-step heat treatments, as characterized via microindentation and atom probe tomography (APT), will be discussed.

9:20 AM
Modeling Liquid Metal Embrittlement Cracks in Cross-tension Spot Weld Testing for Advanced High Strength Steels: Kayla Molnar¹; Matthew Zappulla¹; Kip Findley²; ¹Los Alamos National Laboratory; ²Colorado School of Mines
    While there are many studies to eliminate liquid metal embrittlement (LME) in 3rd generation steels, few studies investigate the influence of LME cracks on mechanical performance. Finite Element modeling was used to examine von Mises stresses at the LME crack tip and weld edge for a 3D cross-tension test. The objective was to identify a crack length and geometry at which the crack tip stress is higher than the weld edge stress, implying the crack degrades mechanical properties and changes the failure mode. Four parametric studies were conducted for each of the crack variables: center angle, arc angle, crack angle and crack length. Cross-tension samples of galvanized TRIP1180 steel, with shoulder LME cracks of various lengths (350 – 1400 μm), were tested quasi-statically for comparison. The results from the models support findings from previous literature and the experimental testing performed, where cracks larger than 1000 μm exhibited significant mechanical degradation.

9:45 AM
Using Computer Vision to Predict Mechanical Properties of High Temperature Alloys: Nan Gao¹; Zongrui Pei²; Youhai Wen²; Michael Gao²; Elizabeth Holm¹; ¹Carnegie Mellon University; ²NETL
    Microstructures governed by their chemical compositions and processing methods affect materials properties. Exploring the linkage between microstructure and properties is especially important to material design of high performance alloys. Microstructures are usually characterized by visual inspection and metallographic measurements. Although morphology information can be captured and observed, the rich, multiscale microstructural feature data contained in a typical micrograph is rarely fully quantified or exploited. In this research, pre-trained convolutional deep neural networks (CNNs) are used to extract information from the microstructures, and regression models are optimized to predict mechanical properties based on characteristic features that exist at a hierarchy of length scales. The yield stress of steel alloys is predicted with good fidelity, and links to microstructural features that influence mechanical response are made. We find that computer vision and machine learning are promising tools for connecting microstructure to properties.

10:10 AM Break

10:25 AM
Computational Design of a High Strength High Toughness Fully-austenitic TRIP Steel: Amit Behera¹; Dana Frankel¹; Fan Meng¹; Peter Jacobson¹; Greg Olson¹; ¹QuesTek Innovations LLC
    QuesTek Innovations LLC utilized its Integrated Computational Materials Engineering (ICME) tools and expertise to design and develop a next generation fully-austenitic TRIP steel aiming at high yield strength, high toughness, and good weldability. Using a systems-based approach focusing on process-structure-property relationships, a cost-effective fully-austenitic TRIP steel composition with optimized homogenization and annealing heat treatment cycle was designed. The designed steel was predicted to have high strength due to gamma-prime precipitation in the austenite matrix and improved toughness due to transformation induced plasticity (TRIP) effect along with achieving other key design criteria such as to avoid formation of detrimental secondary phases, good weldability, avoid excessive grain coarsening. Results from experimental prototyping of the designed steel, its microstructural characterization and mechanical property testing will be discussed. The calibration and validation of developed models to predict the microstructural features and mechanical properties using the experimental results will also be reviewed.

10:50 AM
Properties and Performance of Fe-Mn-Al-C Alloys as a Function of Composition: Krista Limmer¹; Daniel Field¹; Katherine Sebeck²; ¹DEVCOM Army Research Laboratory; ²DEVCOM Ground Vehicle Systems Center
    A series of Fe-Mn-Al-C alloys were produced and evaluated in order to determine the effect of composition variation on resulting properties and performance. Whereas past studies have examined the sensitivity of mechanical properties to changing a single element in the composition in these alloys, this study evaluated covariance of the major elements: Mn, Al, and C. The wrought plates were produced by two vendors according to a 2ł factorial design of experiments that were all expected to be age hardenable through precipitation of κ-carbide. Properties and performance will be discussed in terms of composition, microstructure, and plate quality.