Character and Distribution of Geometrically Necessary Dislocations in Polycrystalline Tantalum

Landon T Hansen; Jay D Carroll; Eric R Homer; Robert H Wagoner; Guowei Zhou; David T Fullwood

doi:10.1093/micmic/ozad049

Character and Distribution of Geometrically Necessary Dislocations in Polycrystalline Tantalum

Microsc Microanal. 2023 Jun 9;29(3):953-966. doi: 10.1093/micmic/ozad049.

Authors

Landon T Hansen¹, Jay D Carroll², Eric R Homer¹, Robert H Wagoner³, Guowei Zhou⁴, David T Fullwood¹

Affiliations

¹ Department of Mechanical Engineering, Brigham Young University, EB 350, Provo, UT 84602, USA.
² Materials Science and Engineering Center, Sandia National Laboratories, 1515 Eubank SE, Albuquerque, NM 87123, USA.
³ Department of Materials Science and Engineering, Ohio State University, 2041 College Rd., Columbus, OH 43210, USA.
⁴ Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.

PMID: 37749696
DOI: 10.1093/micmic/ozad049

Abstract

Geometrically necessary dislocations (GNDs) play a key role in accommodating strain incompatibility between neighboring grains in polycrystalline materials. One critical step toward accurately capturing GNDs in deformation models involves studying the microstructural features that promote GND accumulation and the resulting character of GND fields. This study utilizes high-resolution electron backscatter diffraction to map GND populations in a large polycrystalline sample of pure tantalum, under simple tension. A total of 1,989 grains, 3,518 grain boundaries (GBs), and 3,207 triple junctions (TJs) were examined in a subsurface region of the sample. Correlations between GND density and GB character, and to some extent, TJ character, are investigated. Statistical geometrical relationships between these entities are quantified, and also visualized, using a novel application of two-point statistics. The nature of GNDs across the sample is also visualized and assessed using a recently developed method of mapping the local net Burgers vectors. The different approaches to characterizing GND distribution are compared in terms of how they quantify the size of near boundary gradient zones.

Keywords: geometrically necessary dislocations; grain boundary; high resolution EBSD; near boundary gradient zone; tantalum; triple junction; two-point statistics.