Phase Transformations and Microstructural Evolution: General Topic I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Rongpei Shi, Harbin Institute of Technology; Yipeng Gao, Jilin University; Fadi Abdeljawad, Lehigh University; Bharat Gwalani, North Carolina State Universtiy; Qi An, Iowa State University; Eric Lass, University of Tennessee-Knoxville; Huajing Song, Los Alamos National Laboratory
Thursday 8:30 AM
March 18, 2021
Room: RM 57
Location: TMS2021 Virtual
Session Chair: Qi An, University of Nevada, Reno
8:30 AM
About the Plasticity of Cobalt upon Phase Transformation: A High Temperature Nanoindentation Study: Verena Maier-Kiener1; Johann Kappacher1; Helmut Clemens1; 1Montanuniversitaet Leoben
The plastic deformation behavior of technically pure cobalt with a phase transformation temperature around 710K was investigated in the low temperature hexagonal closed packed and high temperature face centered cubic phase by means of high temperature nanoindentation techniques. Strain-rate jump tests were executed up to 873K to determine strain rate sensitivity, activation volume and activation energy of plastic deformation for identification of the rate-controlling deformation mechanism. From room temperature up to 473K the deformation behavior of the hexagonal phase was found to be controlled by dislocation segments overcoming the Peierls-Nabarro barrier to slip on the basal plane. Deformation twinning was apparent in the hexagonal phase, with rising activity as temperatures increase. The thermal activation of cross-slip leads to reduced twinning actions between 500K and 710K. In the high temperature cubic phase obstacle controlled dislocation glide was found to be the rate controlling mechanism and no deformation twinning was observed.
8:50 AM
Atomistic Modeling of the Twinning fcc/bcc Phase Transformation in Binary Systems: Quasi-particle Approach and Experiment: Gilles Demange1; Helena Zapolsky2; Kaixuan Chen3; Renaud Patte1; Zidong Wang3; Pavel Korzhavyi4; 1CNRS-University Of Rouen Normandy; 2Cnrs-University Of Rouen Normandy; 3University of Science and Technology Beijing; 4 KTH - Royal Institute of Technology
Mechanical properties of metallic alloys strongly depend on their microstructure. In particular, the structure and morphology of precipitates lead to distinct strengthening effects. Recently, it was shown that on the proper range of temperatures, in the fcc CuFeCo system, a twin-like microstructure is formed within Iron rich precipitates. In this work, we applied the quasi-particle approach (QA) [1], recently derived from the continuous atomic density functional approach, to elucidate this phenomenon during casting and aging process. The twinning structure with Kurdjumov-Sachs orientation relationship, twin boundary structure, and fcc-bcc interface structure and propagation mode could be assessed thanks to large scale simulations. [1] Lavrskyi, M., et al., npj Computational Materials, 2, 15013, (2016).
9:10 AM
Data Assimilation-based Approach to Estimate Grain Boundary Properties Using Phase-field Grain Growth Simulations: Eisuke Miyoshi1; Tomohiro Takaki1; Yasushi Shibuta2; Munekazu Ohno3; 1Kyoto Institute of Technology; 2The University of Tokyo; 3Hokkaido University
In actual materials, the energy and mobility of grain boundaries are usually strongly anisotropic, taking different values for each boundary. Such anisotropies in boundary properties are of great importance for predicting and controlling the microstructural evolution of the materials. However, detailed data for the anisotropic properties is still not obtained. This lack of data is attributable to the limitation of conventional measurement methods for grain boundary properties, in which only the product of boundary energy and mobility (i.e. reduced mobility) can be determined.This study proposes a novel framework to estimate anisotropic grain boundary properties via the ensemble Kalman filter-based data assimilation for phase-field simulations, with atomistic simulations or experiments as the observation data. The method allows for separately computing boundary energies and mobilities by calibrating the phase-field input parameters based on the Bayesian inference. Through a series of numerical tests, the validity of the method is examined in detail.
9:30 AM
Effects of Oxygen Interstitials on Phase Transformation Paths in Nb-Ti Alloys: Ravit Silverstein1; Raphaële Clément1; Carlos Levi1; 1University of California, Santa Barbara
Interstitials in multi principal element (MPE) b.c.c. alloys are generally acknowledged to have significant effects on their mechanical properties. At issue is understanding the interaction of O with MPE alloys containing elements from groups IVB, VB and VIB, the potential effects on the elemental distribution, and the consequences for mechanical behavior. This study addresses the effect of O incorporation in a binary Nb-Ti solid solutions as a baseline for subsequent studies in ternary and higher order MPE alloys. Alloys were splat quenched to refine segregation during solidification and to enable homogenization in reasonable times. Some splats were encapsulated and heat treated in 16O environments while others were crushed into powders and heat treated in 17O environments for NMR studies. The structure evolution upon O infusion was examined using transmission electron microscopy and solid state NMR. The studies provide insight into the phase transformations resulting from O ingress.
9:50 AM
In Situ Transformations during Heating of Copper-intercalated Bismuth Telluride: Pralav Shetty1; Matthew McDowell1; 1Georgia Institute of Technology
Layered materials have received considerable attention owing to their exceptional properties. The presence of a van der Waals gap between individual layers enables the intercalation of species which can be used for tuning these properties. Intercalation can also be an unintended consequence of diffusion from patterned contacts on the layered materials. Intercalation of species into a layered material may lead to unanticipated structural and phase transformations. These transformations can be further exacerbated at elevated temperatures, yet little is understood about the high-temperature dynamics that occur in these systems. Here, we utilize in situ transmission electron microscopy to reveal nanoscale transformations during heating of Cu-intercalated Bi2Te3 crystals. We show that Cu reduces thermal stability, and the intercalated Cu first orders within the Bi2Te3 crystal at moderate temperatures before causing a transformation to crystallographically-aligned Cu2Te at higher temperatures. Our results have important ramifications for the design of layered material devices.
10:10 AM
Intrinsic Coupling between Phase Transformation and Deformation Twinning: Yipeng Gao1; 1The Ohio State University
Phase transformation and deformation twinning are two important mechanisms that can generate a variety of microstructures in metallic materials. Although both of them are symmetry-breaking processes and theories to treat each of them individually have been well-established, the intrinsic coupling between the two has not been investigated. Here we employ a phase transition graph approach to analyze systematically deformation modes arising from the interplay between phase transformation and deformation twinning. Using typical BCC metals as examples, we show that mechanical twinning and phase transformations are intrinsically coupled through correlated broken symmetry, which results in multiple interconnected transformation and non-transformation deformation pathways and characteristic twinning modes. This work not only reveals the physical origin of unique twinning modes recently observed in experiments, but also establishes a theoretical foundation to place phase transformation and deformation twinning on an equal footing from a crystallographic point of view.
10:30 AM
Beyond Modified Mean Field: A Solution for a Stochastic Grain Growth Model in the Short Time Limit: Alex Moser1; Chandra Pande1; 1U.S. Naval Research Laboratory
We discuss the basic mechanism of grain growth in three dimensions in metals and alloys. It is argued, a comprehensive grain growth model is best based on a stochastic process described by a Fokker Planck equation. We show that this concept is sufficient to determine almost all features of grain growth in general terms. The existence of the von Neumann law and its counterpart in three dimensions enables us to provide an explicit form of the Fokker Planck equation and thus determine many features of grain growth in great detail in the long time limit. Finally, we illustrate an analytical solution for three dimensional grain growth in the short time limit.