Grain Boundaries, Interfaces, and Surfaces: Fundamental Structure-Property-Performance Relationships: Mechanics at Interfaces
Sponsored by: ACerS Basic Science Division
Program Organizers: Shen Dillon, University of California, Irvine; Wolfgang Rheinheimer, University of Stuttgart; Catherine Bishop, University of Canterbury; Ming Tang, Rice University; John Blendell, Purdue University; Wayne Kaplan, Technion - Israel Institute Of Technology; Melissa Santala, Oregon State University
Monday 2:00 PM
October 10, 2022
Room: 323
Location: David L. Lawrence Convention Center
Session Chair: Shen Dillon, University of California, Irvine; John Blendell, Purdue University
2:00 PM Invited
Alteration of Microstructures by Stressing Surfaces and Interfaces: Klaus van Benthem1; 1University of California, Davis
Mechanical, electrical or chemical stress on surfaces or interfaces affects surface and interface energies and can therefore determine microstructure evolution. In this presentation a series of recent bicrystal diffusion bonding experiments will be reviewed that were designed to interrogate electric field effects on the atomic and electronic structures of individual grain boundaries. The results demonstrate the ability to alter grain boundary configurations and, hence, interface energies in an emerging microstructure. In a separate study growth of NiO nanorods from individual Ni nanoparticles was observed during in-situ electron microscopy at high temperature and in the presence of water vapor. High-aspect ratio growth of NiO is favored for sufficiently high total surface energies. In-situ high resolution transmission electron microscopy experiments were used to verify that the terrace-ledge-kink model is also applicable to reactive crystal growth. This work was financially supported by the US National Science Foundation under award DMR-1836571.
2:30 PM
Grain-boundary Energy Variation and Evolution during Dislocation-assisted Grain-boundary Sliding in Polycrystaline Mg2SiO4 – Linking Earth and Materials Sciences: Katharina Marquardt1; Alexandra Austin1; Marina Sedlak1; Filippe Ferreira2; Lars Hansen3; Sanae Koizumi4; 1Imperial College; 2University of Heidelberg; 3University of Minnesota; 4University of Tokyo
Forsterite, the Mg-endmember of the olivine solid solution, is a refractory material of interest for high-temperature engineering applications and well studied in relation to its abundance in Earth’s upper mantle. The microstructure and physical properties of polycrystalline forsterite are controlled by the anisotropy of grain-boundary energy and its evolution in conjunction with dynamic processes such as deformation and recrystallization.Here we compile results from recent investigations of (i) variation in grain-boundary energy anisotropy variation studied using AFM and grooving, (ii) grain-boundary population from EBSD measurements, and (iii) the evolution of these distributions during deformation in the dislocation-assisted grain-boundary sliding regime. The change in plane populations, as well as grain size, are key factors influencing the interconnectivity of melt, the extractability of melt from the upper mantle, and the attenuation of seismic waves.
2:50 PM Invited
Atomistic Dynamics of Deformation, Fracture and GB Migration in Oxides: Yuichi Ikuhara1; 1Univ.Tokyo, JFCC, Tohoku University
In order to clarify the deformation and fracture mechanism in oxides such as Al2O3 and STO, TEM in situ nanoindentation experiments were conducted for their single crystals and bicrystals. We successfully observed the dynamic behavior of twin formation, twin-GB interaction, pile-up dislocation, jog and kink formation and jog drag dynamics and so on. The mechanism of each dynamic behavior will be discussed in detail in this presentation. GB migration plays an important role in considering the high temperature mechanical properties. Recently, we have found that GB migration behavior in Al2O3 can be precisely controlled by the aid of the high-energy electron beam irradiation. This technique was applied to directly visualize the atomistic GB migration. It was revealed that the GB migration is processed by a cooperative shuffling of atoms in GB ledges along specific routes.
3:20 PM Break
3:40 PM Invited
The Role of Grain Boundaries in Nucleation-controlled Plasticity of Metal Nanoparticles: Eugen Rabkin1; Amit Sharma2; Jonathan Amodeo3; Tatyana Fedyaev1; Anuj Bisht1; Olivier Thomas3; 1Technion; 2Empa; 3Aix Marseille Univ., Université de Toulon, CNRS
We demonstrated that coating single crystalline Ag nanoparticles with a thin polycrystalline Au layer leads to mechanical weakening of the particles. Moreover, while the single crystalline Ag nanoparticles yield in a single large displacement burst when loaded in compression, their Ag-Au core-shell counterparts demonstrate a more homogeneous deformation with signs of strain hardening. On the contrary, twinned nanoparticles of the homogeneous Ag-Au alloys yield in a similar manner and at a comparable stress as single crystalline Ag particles. Our molecular dynamics simulations demonstrate that weakening of the core-shell particles at low strains is attributed to the dislocation nucleation at the random grain boundaries in the polycrystalline Au shell, and at the Ag-Au interphase boundary. Coherent twin boundaries are not as efficient as random ones in nucleation of new dislocations.
4:10 PM
Cracking in a Reacted Layer Material: C. Barry Carter1; Chanchal Ghosh1; Manish Singh1; Matthew Janish1; Shayani Parida1; Arthur Dobley1; Avinash Dongare1; 1University of Connecticut
In this study, the reaction between Li/Li2O and MoS2 has taken place in the transmission electron microscope (TEM) with the basal plane in the edge-on orientation; nanolayers of reacted material were observed to develop in real-time as the Li moved into the gaps followed by the formation of so-called ‘white-line defects’. Energy-filtered TEM (EFTEM) analysis shows that these lines are rich in Li and poor in Mo and S. Atomic-resolution TEM studies in an aberration-corrected TEM show the different stages of the microstructural evolution along these white line defects. The present paper will discuss the cracking that can then can occur along these white-line defects when a relatively small external stress is applied. This cracking subsequently leads to exfoliation and the structural degradation of the intercalated material and is directly relevant to understanding the safe operation and reliability of future lithium-ion batteries. These direct observations are complemented by atomistic modeling.
4:40 PM
Characteristics of Steady State and a Scale Law of Plastic Deformation: Yan Huang1; 1Brunel University London
Steady state deformation was characterized based on the experimental results of dilute single-phase aluminum alloys. It was found that, although the characteristic properties such as flow stress and grain size remained constant with time, continuous loss of grain boundaries occurred as an essential feature at steady state. A physical model, considering the activities of grain boundary dislocations, was developed to describe the kinetics of steady state deformation. According to this model, steady state as a function of strain rate and temperature is the very turning point of grain size and strength relationship, i.e., Hall-Petch relation holds when grain size is larger than that at the steady state or inverse Hall-Petch relation takes over if grain size is smaller. The transition between the two relationships is a phenomenon depending on deformation conditions, rather than an intrinsic property as generally perceived. A general scale law deformation is established accordingly.