{"title":"High-voltage electron microscopy analyses for crack-tip dislocations and their shielding effect on fracture toughness in MgO and Si crystals","authors":"Kenji Higashida, Sunao Sadamatsu, Masaki Tanaka","doi":"10.1111/jace.20378","DOIUrl":null,"url":null,"abstract":"<p>In this study, characteristics of dislocation structures around a crack-tip in both crystals of MgO and Si were investigated using high-voltage electron microscopy (HVEM). The interaction between a crack and dislocations was analyzed to discuss the effect of crack-tip plasticity on fracture toughness. The present paper first demonstrates a dislocation configuration around a crack-tip in a MgO thin crystal, where the plastic zone called 45°-shear type is dominant under the plane stress condition. Then, the slip systems necessary for brittle-to-ductile transition in ionic crystals with the rock-salt structure are discussed based on the temperature dependence of stress-strain relationships and the aspect of crack front observed in NaCl crystals. Second, crack-tip dislocations near the surface of bulk Si crystals are exhibited based on the 3D analyses using HVEM tomography. We focus on a newfound plastic zone being perpendicular to the crack plane, which is different from either 45°-shear type or the hinge type generally well-known. The dislocation loops observed in this plastic zone fundamentally have a crack-tip shielding effect to increase fracture toughness. Still, in addition, they contribute to activating crack-tip dislocations by their localized antishielding field. These analyses reveal a fundamental toughening mechanism for crystalline materials.</p>","PeriodicalId":200,"journal":{"name":"Journal of the American Ceramic Society","volume":"108 6","pages":""},"PeriodicalIF":3.5000,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the American Ceramic Society","FirstCategoryId":"88","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/jace.20378","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, CERAMICS","Score":null,"Total":0}
引用次数: 0
Abstract
In this study, characteristics of dislocation structures around a crack-tip in both crystals of MgO and Si were investigated using high-voltage electron microscopy (HVEM). The interaction between a crack and dislocations was analyzed to discuss the effect of crack-tip plasticity on fracture toughness. The present paper first demonstrates a dislocation configuration around a crack-tip in a MgO thin crystal, where the plastic zone called 45°-shear type is dominant under the plane stress condition. Then, the slip systems necessary for brittle-to-ductile transition in ionic crystals with the rock-salt structure are discussed based on the temperature dependence of stress-strain relationships and the aspect of crack front observed in NaCl crystals. Second, crack-tip dislocations near the surface of bulk Si crystals are exhibited based on the 3D analyses using HVEM tomography. We focus on a newfound plastic zone being perpendicular to the crack plane, which is different from either 45°-shear type or the hinge type generally well-known. The dislocation loops observed in this plastic zone fundamentally have a crack-tip shielding effect to increase fracture toughness. Still, in addition, they contribute to activating crack-tip dislocations by their localized antishielding field. These analyses reveal a fundamental toughening mechanism for crystalline materials.
期刊介绍:
The Journal of the American Ceramic Society contains records of original research that provide insight into or describe the science of ceramic and glass materials and composites based on ceramics and glasses. These papers include reports on discovery, characterization, and analysis of new inorganic, non-metallic materials; synthesis methods; phase relationships; processing approaches; microstructure-property relationships; and functionalities. Of great interest are works that support understanding founded on fundamental principles using experimental, theoretical, or computational methods or combinations of those approaches. All the published papers must be of enduring value and relevant to the science of ceramics and glasses or composites based on those materials.
Papers on fundamental ceramic and glass science are welcome including those in the following areas:
Enabling materials for grand challenges[...]
Materials design, selection, synthesis and processing methods[...]
Characterization of compositions, structures, defects, and properties along with new methods [...]
Mechanisms, Theory, Modeling, and Simulation[...]
JACerS accepts submissions of full-length Articles reporting original research, in-depth Feature Articles, Reviews of the state-of-the-art with compelling analysis, and Rapid Communications which are short papers with sufficient novelty or impact to justify swift publication.