Defect and Phase Transformation Pathway Engineering for Desired Microstructures: Invited Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Yufeng Zheng, University of North Texas; Rongpei Shi, Harbin Institute of Technology; Yipeng Gao, Jilin University; Timofey Frolov, Lawrence Livermore National Laboratory; Stoichko Antonov, National Energy Technology Laboratory; Jessica Krogstad, University of Illinois at Urbana-Champaign; Bin Li, University Of Nevada, Reno

Tuesday 8:30 AM
March 16, 2021
Room: RM 55
Location: TMS2021 Virtual

Session Chair: Yufeng Zheng, University of Nevada Reno; Rongpei Shi, Lawrence Livermore National Laboratory


8:30 AM  Invited
New Insights on Deformation Twinning- Mechanisms and Modeling: Huseyin Sehitoglu1; ASK Mohammed1; Orcun Celebi1; Gorkem Gengor1; Jessica Krogstad1; 1University of Illinois
    There has been considerable recent interest in twinning deformation in metals. In this presentation, some of the previous observations and models on twinning are reviewed. We present advanced models for twinning utilizing a combination of atomistic and meso-scale descriptions. We consider cubic, ordered and hcp crystals in our calculations. Some of the new developments in modeling of twinning (the role of shears, shuffles and offsets) will be reviewed and the importance of twinning in monotonic deformation and fatigue studies will be also highlighted. We show theoretically the description of the twin plane in shape memory alloys and precisely how twin migrates. We show the complex twinning modes in B2 and hcp crystals. We discuss the topic of twin-slip interactions and how these interactions result in strengthening of metals due to complex dislocation core evolution at slip-twin intersections.

8:50 AM  Invited
Phase Transformation Pathways in High Entropy Alloys or Complex Concentrated Alloys mediated by Defects: Sriswaroop Dasari1; Bharat Gwalani1; Yao-Jen Chang2; Deep Choudhuri1; Stephane Gorsse3; An-Chou Yeh2; Rajarshi Banerjee1; 1University of North Texas; 2National Tsing Hua University; 3University of Bordeaux, France
    This presentation will demonstrate the strong influence of defects, induced by thermo-mechanical processing, on the phase transformation pathway adopted for second-phase precipitation in high entropy alloys (HEAs) or complex concentrated alloys (CCAs), such as Al0.3CoCrFeNi, Al0.5Co1.5CrFeNi1.5, and Al0.3CoFeNi. A thermo-mechanical processing sequence of homogenization - cold-rolling - solution treatment, followed by a precipitation anneal at a lower temperature, results in homogeneous nanometer scale-ordered L12 (gamma prime-like) precipitates within the face-centered cubic (FCC) matrix. Contrastingly, if the cold-rolled alloys is directly annealed at the precipitation temperature, then the resulting microstructural evolution pathway changes completely, with precipitation of B2 phase, either at the grain boundaries of recrystallized FCC grains and/or on twins and deformation bands within non-recrystallized grains. These experimentally observed variations in transformation pathway have been rationalized via the competition between the thermodynamic driving force and activation barrier for second-phase nucleation in this alloy, coupled with the kinetics of the process.

9:10 AM  Invited
Microstructure and Tensile Behavior of Nanostructured Gradient TWIP Steel: Jie Ding1; Zhongxia Shang1; Jin Li1; Haiyan Wang1; Xinghang Zhang1; 1Purdue University
    Gradient structured metals have shown unique mechanical properties, such as high strength and good ductility. In this study, a gradient twinning-induced plasticity (TWIP) steel was fabricated by surface mechanical grinding treatment (SMGT). The subsequent gradient structures consist of an outermost nanolaminate layer, a layer of deformation twins mixed with shear bands, and a deformation twinned layer. Tensile studies reveal that the introduction of gradient structures increases the yield strength significantly. Deformation induced hardening reaches maxima at the interface regions between the layers, presumably due to the distinct transition of high angle grain boundaries and twin boundaries near the interfaces and the accumulation of geometrically necessary dislocations under tension. These in-depth studies provide insight into the design of high-strength, strain hardenable metallic materials with gradient structures.

9:30 AM  Invited
Kinetic Monte Carlo Simulations of Solute Clustering in Multicomponent Al Alloys: Mingfei Zhang1; Zhucong Xi1; Louis Hector Jr.1; Chaoming Yang1; Liang Qi1; 1University of Michigan
    High-strength multicomponent aluminum (Al) alloys have significant formability limitations due to fast precipitate kinetics at room temperature (natural aging) associated with the nucleation and growth of solute clusters and Guinier-Preston (GP) zones. Slowing the natural aging is crucial to expand the time window between alloy manufacturing and mechanical forming of these Al alloys at room temperature. Intending to understand and slow the precipitate kinetics, we developed a kinetic Monte Carlo (kMC) simulation framework to study the nucleation and growth of solute clusters in multicomponent Al alloys. Our kMC method includes an artificial neural network (ANN) model trained by many (>1000) first-principles DFT calculations to predict vacancy migration barriers in Al-Mg-Zn alloys accurately. This ANN has demonstrated that the widely used linear relations between the thermodynamic driving forces and the migration barriers are inaccurate for Al-Mg-Zn alloys. This discovery will have a profound impact on studies of multicomponent alloy kinetics.

9:50 AM  Invited
Grain Boundary Segregation in Immiscible Alloys: Anisotropy and Trijunction Effects: Anne Barnett1; Michael Cox1; Derek Moore1; Maher Alghalayini1; Chris Barr2; Khalid Hattar2; Brad Boyce2; Fadi Abdeljawad1; 1Clemson University; 2Sandia National Laboratories
    Nearly all structural and functional materials are multicomponent polycrystalline systems. In these materials, the interaction of elemental species with grain boundaries (GBs) greatly influences many of their observable properties. In this talk, we present results from atomistic simulations and mesoscale phase field models highlighting the role of GB solute segregation in microstructure development and evolution in immiscible alloys. It is found that the interplay between GB solute segregation and bulk thermodynamics determines the extent of solute partitioning between bulk grains and GBs, thus affecting the resultant microstructures. Further, simulation results supported by recent high-resolution experimental findings highlight the paramount roles of trijunction solute segregation and GB segregation anisotropy in the microstructural evolution of these materials systems. In broad terms, our results provide future avenues to explore interface segregation as a tool to design materials with tailored microstructures.

10:10 AM  Invited
Development of Superalloys Driven by Atomic-scale Interactions of Solutes with Crystal Defects: Paraskevas Kontis1; Stoichko Antonov1; Philipp Kürnsteiner1; Shyam Katnagallu2; Jaber Mianroodi1; Lola Lilensten3; 1Max-Planck-Institut für Eisenforschung GmbH; 2Karlsruhe Institute of Technology; 3CNRS - Institut de Recherche de Chimie Paris
    Solutes constantly interact with moving crystal defects generated by the plastic deformation of an alloy. These interactions are not well understood, yet they control the structural integrity of safety-critical components in e.g. aero-engines. Understanding how solutes interact with defects during service and thermomechanical processing can pave the way towards unlocking new alloy design strategies. Through systematic high resolution characterization at the near-atomic scale by electron microscopy and atom probe tomography, we provide new fundamental insights into the physical interactions of solutes with crystal defects in deformed single crystal and polycrystalline superalloys. We will present how the partitioning of solutes at defects depend on the alloy composition, type of defect and deformation conditions. Besides, we will show how these interactions affect the desired microstructure during thermomechanical processing of polycrystalline superalloys. Finally, atomistic phase field simulations reveal insights into the role of defect velocity on the partitioning of solutes partitioning at defects.

10:30 AM  Invited
Evolution of Metastable Grain Boundaries and Its Implications on Nanocrystals’ Hardness Variation: Zhitong Bai1; Glenn Balbus2; Daniel Gianola2; Yue Fan1; 1University of Michigan; 2UCSB
    Recent experiments show that nanocrystals can be rejuvenated by pulsive femtosecond laser and their hardness can be effectively tuned. However, a mechanistic understanding on such phenomenon remains unclear. Here we investigate the evolution of a multiplicity of metastable grain boundaries in Cu under fast driving conditions using atomistic modeling techniques. A universal hysteresis is observed, and the GB is driven to a higher energy state after pulsive stimuli. Using enhanced data-mining algorithm to analyze the annealing behavior of GBs at various conditions, we construct a high-resolution pixel map for GB’s energetic evolution, showing that it is divided into an ageing regime and a rejuvenating regime over the energy—temperature space. The ageing/rejuvenating origin is attributed to the energy imbalance during the interchanges between the GB’s metastable states. A self-consistent kinetic equation is derived to capture the GB’s energetic and mechanical responses to external stimuli, which can explain the experimental observation.