Grain Boundaries, Interfaces, and Surfaces: Fundamental Structure-Property-Performance Relationships: Processing and Microstructure
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
Wednesday 2:00 PM
October 12, 2022
Room: 323
Location: David L. Lawrence Convention Center
Session Chair: Shen Dillon, University of California, Irvine; Melissa Santala, Oregon State University
2:00 PM Invited
Measurements of 3D Microstructures to Determine Grain Boundary Velocities in Polycrystals: Gregory Rohrer1; 1Carnegie Mellon University
Using high-energy diffraction microscopy, we have measured the velocities of grain boundaries within Ni and Fe polycrystals. Thousands of grain boundaries were tracked and their velocities and curvatures were classified by their crystallographic characteristics. Among the findings, two are noteworthy and will be discussed in this talk. First, the velocities vary with all five crystallographic grain boundary parameters. Second, grain boundary velocity is independent of grain boundary mean curvature. Because curvature is an important component of the driving force, velocity and curvature are expected to be correlated positively. However, the evidence for such a correlationis poor. Three possible explanations for these observations will be presented: constrained migration of boundaries in connected networks, defect (disconnection) mediated grain boundary migration, and the influence of grain boundary stiffness on migration.
2:30 PM
Grain Growth Study of Strontium Titanate: Comparison between High Energy X-ray Diffraction Microscopy and Simulation: Vivekanand Muralikrishnan1; He Liu2; Lin Yang1; Robert Suter2; Michael Tonks1; Gregory Rohrer2; Amanda Krause1; 1University of Florida; 2Carnegie Melon University
Understanding how individual grain boundaries (GBs) migrate during grain growth is essential for microstructural design and, thus, improved performance. However, the mechanisms of GB migration in a polycrystal are still unclear. Non-destructive 3D X-ray diffraction microscopy provides an opportunity to observe individual GB evolution when subjected to annealing and hence correlate GB migration in a polycrystalline material to local microstructural features. Here, non-destructive high energy diffraction microscopy (HEDM) measurements of strontium titanate (SrTiO3) will be used to investigate the classical relationship between GB velocity and curvature in a polycrystal. The experimentally observed growth behavior will be compared to that in isotropic grain growth simulations to identify how GB character or energy relate to GB motion. The results from this study will provide insights into how simulations can be improved to better predict microstructural evolution.
2:50 PM Invited
Characterizing Interface Diffusion Mechanisms in Al and Al-Si Alloys via Atomistic Simulations: Ian Chesser1; Raj Koju1; Yuri Mishin1; 1George Mason University
Interface diffusion and interfacial slip are two key processes contributing to the high-temperature creep deformation of metal-matrix composites. Fundamental understanding of these processes remains poor. Atomistic simulations are a promising route toward understanding, but reliable methodology for measuring kinetic coefficients and disentangling competing mechanisms has not been developed. Here, we compare interface diffusion coefficients and mechanisms in pure Al grain boundaries to those in Al-Si phase boundaries for a range of interface types. Some features of interface diffusion are found to be universal, including the existence of collective diffusion mechanisms and dynamical heterogeneity. The Al-Si phase boundaries exhibit additional complexity, including possible glassy behavior and processing-history dependent ordering effects.To identify rate controlling mechanisms of interfacial creep, shear deformation simulations are conducted for selected phase boundaries over a range of strain rates. Interface diffusion and sliding mechanisms are found to be distinct, but correlated processes.
3:20 PM
Grain Boundary Character and Relative Energy Distributions in Nanocrystalline Metallic Films: Matthew Patrick1; Gregory Rohrer2; Katayun Barmak1; 1Columbia University; 2Carnegie Mellon University
Grain boundary character distributions (GBCD) and relative grain boundary energy distributions (GBED) are routinely calculated from 3D serial-section electron backscatter diffraction (EBSD) data from microcrystalline bulk samples, and are found to be inversely correlated. For nanocrystalline thin films, precession electron diffraction (PED) has proven an effective method to measure the GBCD, but the GBED has not been reconstructed. Here, we attempt to adapt the established energy reconstruction method to PED data from films with columnar grain structures, where serial sectioning is not required to determine boundary inclination. The relative GBED does not, however, correlate with Read-Shockley-Wolf (RSW) calculated energies nor does it inversely correlate with the GBCD for either a 40 nm-thick tungsten film or a set of three 100 nm-thick aluminum samples. This failure likely implies that the assumed Herring condition of force balance does not fully specify the geometry at triple junctions in these films.
3:40 PM
Fundamental Structure-Property-Performance Relationships of Unidirectional Grain Boundaries, Interfaces, and Surfaces during SHS Processing: Borys Sereda1; Iryna Kruhliak1; Dmytro Sereda1; Dmytro Kruhliak1; 1Dneprovsky State Technical University
To improve the magnetic characteristics of armco-iron, such as magnetic permeability and coercive force, samples were processed in conditions of self-propagating high-temperature synthesis. Heating was carried out to a temperature of 900 ° C, followed by isothermal holding and cooling at various speeds. The study of the microstructure of samples with a carbon content of up to 0.015% showed that grain boundaries are formed, which are divided into three unidirectional sections. Areas are established where both ends of the boundary enter triple joints with opposite angles exceeding 170 or quadruple joints are observed. Due to the non-stationary stage of the SHS process, a fine-grained structure is formed, which leads to an increase in the coercive force from 0.97 A/cm to 1.65 A/cm and, accordingly, to an increase in hardness from 95 to 157 HB.