Grain Boundaries and Interfaces: Metastability, Disorder, and Non-Equilibrium Behavior: Special Interfaces: Twins, Laminates, etc
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Computational Materials Science and Engineering Committee, TMS: Chemistry and Physics of Materials Committee, TMS: Phase Transformations Committee
Program Organizers: Yue Fan, University of Michigan; Liang Qi, University of Michigan; Jeremy Mason, University of California, Davis; Garritt Tucker, Colorado School of Mines; Pascal Bellon, University of Illinois at Urbana-Champaign; Mitra Taheri, Johns Hopkins University; Eric Homer, Brigham Young University; Xiaofeng Qian, Texas A&M University
Wednesday 8:30 AM
March 2, 2022
Room: 304C
Location: Anaheim Convention Center
Session Chair: Yue Fan, University of Michigan, Ann Arbor; Liang Qi, University of Michigan, Ann Arbor
8:30 AM Invited
Twin-boundary Structural Phase Transitions in Elemental Titanium: Mohammad Hooshmand1; Ruopeng Zhang2; Yan Chong1; Enze Chen1; Timofey Frolov3; David Olmsted1; Andrew Minor1; Mark Asta1; 1University of California, Berkeley; 2Lawrence Berkeley National Laboraory; 3Lawrence Livermore National Laboratory
Twinning in crystalline materials plays an important role in many transformation and deformation processes, where underlying mechanisms can be strongly influenced by the structural, energetic and kinetic properties of associated twin boundaries (TBs). The possibility that TBs can display multiple complexions with distinct properties, and phase transitions between them, has not been widely explored, even though such phenomena are established more generally in grain boundaries. We report experimental findings that {11-24} TBs in titanium display a thick interfacial region with crystalline structure distinct from the bulk. First-principles calculations establish that this complexion is linked to a metastable polymorph of titanium, and exhibits behavior consistent with a solid-state wetting transition with compressive strain, and a first order structural transition under tension. The findings document rich TB complexion behavior in an elemental metal, with potentially important implications for mechanical behavior and phase-transformation pathways.
9:00 AM Invited
Migration Free Energy of Twin Boundaries and Other Crystalline Defects: David Rodney1; Yuji Sato2; Arnaud Allera1; Thomas Swinburne3; 1Lyon University; 2Tokyo University; 3Aix Marseille University
The thermally-activated migration of crystalline defects, such as twin boundaries or dislocations, can be modeled using the transition state theory. Computing activation free energies remains however computationally challenging. Approximations are classically used but often without justification. In particular, a harmonic approximation is often used with the entropic term incorporated as a constant in the attempt frequency. Here we take advantage of a recent linear scaling method, the projected average force integrator (PAFI) method, that fully accounts for anharmonic thermal vibrations, to compute in three-dimensional cells, the activation free energy for {1012} twin boundary migration under stress. We find a strongly stress-dependent entropic contribution and show that the harmonic approximation overestimates the twin migration velocity above 100K, the discrepancy reaching several orders of magnitude at high temperatures. We extend these calculations to screw dislocations in BCC metals, where entropy is also found to play a crucial, yet so far unrecognized, role.
9:30 AM
Thermal Stability and Mechanical Behavior of Immiscible Cu-Ag/Fe Triphase Multilayers with Triple Junctions: Tongjun Niu1; Yifan Zhang2; Jaehun Cho1; Nicholas Richter1; Tianyi Sun1; Haiyan Wang1; Xinghang Zhang1; 1Purdue University; 2Los Alamos National Laboratory
Multilayers often suffer from high temperature microstructure instability due to thermal grooving and subsequent layer pinch-off. Here we report on the enhanced thermal stability of immiscible triphase Cu-Ag/Fe multilayer with triple junctions comparing to Cu/Fe multilayers. The Cu/Fe multilayers experienced drastic grooving and rapid grain growth at 500 °C, followed by the complete breakdown of layer structure and spheroidization at 600 °C. In comparison, the layer structures of Cu-Ag/Fe multilayers remain stable up to 600°C with insignificant grain coarsening. A modified Mullins model was used to estimate the grooving kinetics, and the underlying mechanisms leading to the excellent thermal stability of the triphase multilayers are discussed. The mechanical response of Cu-Ag/Fe and Cu/Fe multilayer was further investigated using in-situ micropillar compressions tests. Comparing to Cu/Fe multilayer, Cu-Ag/Fe multilayer exhibited higher strength and better work hardening capability, where triphase triple junctions may play substantial role in engaging dislocations.
9:50 AM
Disconnection-mediated Transition in Segregation Structure at Twin Boundaries: A Molecular Dynamic Simulation of Platinum-gold System: Chongze Hu1; Douglas Medlin1; Remi Dingreville1; 1Sandia National Laboratories
Twin boundaries can significantly control the stability and mechanical properties of many nanocrystalline materials. Thus, understanding their atomic-level structure and chemistry is important to optimize fabrication recipes for improving the properties of nanocrystalline materials. In this talk, we will discuss a novel grain boundary transition in segregation structure driven by the disconnection (i.e., step plus dislocation) in gold-decorated platinum twin boundaries. By performing first-principles calculations and molecular dynamic simulations, we show that gold segregation can transition from alternating bilayer structure to trilayer segregation-only structure when the disconnection contains the stacking fault in twin boundary. Such a behavior has been observed for various faulted disconnections with different heights and dislocation features. We further demonstrate that this transition can be explained by the local pressure drop and increasing of segregation volume across the stacking faults, which is also supported by classical Langmuir-Mclean isotherms.
10:10 AM Break
10:25 AM Invited
Disconnections and Other Defects Associated with Twin Interfaces: Jian Wang1; 1University of Nebraska-Lincoln
Motion of the disconnections along the interface produces both the transformation deformation and the interface motion. Historically, grain boundaries have often been modelled as arrays of dislocations. In low-angle boundaries, the separation of individual dislocations is sufficient for regions of distorted single crystal to be discerned. Such regions can be regarded as naturally commensurate terraces. In the high-angle regime, the cores of the component dislocations overlap, and alternative descriptions of their structures are helpful. Thus, the structure of twin boundaries can be regarded as naturally coherent homo-epitaxial terraces. In this lecture, our objective is to concentrate on defects relevant to interface motion, and these exhibit dislocation, disclination, or step character, or some combination thereof. We take twinning in hcp metals as many defect examples. The definition of shuffles within the topological model and the concept of partitioning of the rotational component are presented.
10:55 AM
Nudged Elastic Band-based Modeling of Stress-dependent Twin Boundary Migration in Magnesium: Kehang Yu1; Xin Wang1; Subhash Mahajan2; Timothy Rupert1; Irene Beyerlein3; Penghui Cao1; Julie Schoenung1; Enrique Lavernia4; 1University of California, Irvine; 2University of California, Davis; 3University of California, Santa Barbara; 4National Academy of Engineering
Twin thickening occurs by the migration of the twin boundary upon deformation and serves as a mechanism for accommodating plastic strain. Twin boundary migration is strongly affected by the local stress state, which is hard to determine experimentally. We investigate {10-12} coherent twin boundary (CTB) migration in magnesium under various stress fields using the nudged elastic band method to calculate its minimum energy path. Our results reveal an appreciable influence of a non-glide stress on CTB migration in addition to that of the resolved shear stress. Specifically, a compressive normal stress makes it significantly easier for CTB migration to occur, even under subcritical shear stresses. We formulate a model to describe the evolution of the energy barrier as a function of stress. We also find that the configuration of twinning disconnections depends on the applied stress field and exhibits a compression-tension asymmetry.
11:15 AM
Amorphous/Crystalline Interfaces in Nanomultilayers: Kyle Russell1; 1University of Southern California
Nano-designed materials possess extraordinary material properties such as high hardness, corrosion resistance, and radiation damage resistance. Although significant research has focused on understanding the properties of interfaces, the scope has been largely limited to studying crystalline systems. The fundamental mechanisms dictating the behavior of amorphous/crystalline and amorphous/amorphous interfaces have yet to be thoroughly examined and understood. Particular nanostructured systems, such as multilayers, lend themselves well towards studying interfaces in highly-disordered systems. Nanometallic multilayers consist of alternating layers of metals and/or ceramics with individual layer thicknesses on the order of several nanometers. Such systems allow for a high degree of customization as individual layer compositions and structures can be tailored through altering synthesis parameters. In this talk, sputtered amorphous and crystalline ferritic multilayers are synthesized and characterized to elucidate on the characteristics and behavior of interfaces at elevated temperatures.
11:35 AM
Irrationalities and Non-unique Lattice Correspondences across Interfaces in Shape Memory Alloys: Ahmedsameerkhan Mohammed1; Sidharth Ravi1; Wael Abuzaid2; Hiroshi Akamine3; Minoru Nishida3; Huseyin Sehitoglu1; 1University of Illinois Urbana Champaign; 2American University of Sharjah; 3Kyushu University
Shape Memory Alloys (SMAs) are phase-transforming materials capable of sustaining large reversible strains. Their reversibility depends on the motion of the transformation front and internal Twin Boundaries (TBs) in the transformed phase. We propose a thorough clarification of irrational internal TBs in 4 SMA alloys, revealing the partitioning of twinning shear on the irrational plane into shear on rational terraces and a non-trivial coherence strain on terraces. This coherence strain is relieved by an array of interface dislocations where the spacing between them can evolve with glide. The transformation front separates phases related by a lattice correspondence. TEM and EBSD observations in the new SMA, FeMnNiAl, independently observed the Nishiyama-Wasserman, Kurdjumov-Sachs and Pitsch correspondences revealing its non-unique nature. We explain all observations based on Habit-Plane-Variant (HPV) predictions from energy-minimization theory, noting that distinct correspondences can be obtained depending on internal structure of the transformed phase, whether twinned or faulted.