{"title":"CoCrNi中熵合金的压痕尺寸效应:部分位错和变形孪晶的作用","authors":"Xuekun Shang , Zhiyuan Liang , Binbin He","doi":"10.1016/j.ijplas.2025.104428","DOIUrl":null,"url":null,"abstract":"<div><div>In this study, we investigated the indentation size effect (ISE) in a CoCrNi medium-entropy alloy using nanoindentation experiments and transmission electron microscopy (TEM) observations. Interestingly, the depth-hardness curves of two grains with different crystal orientations exhibit a crossover phenomenon together with orientation-dependent twinning behaviour. Comprehensive TEM characterization revealed that plastic deformation was accommodated by perfect dislocation slip in the [0 1 1]-oriented grains, whereas it involved dislocation slip, stacking faults, and deformation twins in the [0 0 1]-oriented grain. Partial dislocation slip was found to dominate in the [0 0 1]-oriented grain at very small depths, thereby suppressing dislocation motion and cross-slips, resulting in a higher dislocation density and increased hardness. A modified Nix-Gao model, incorporating partial dislocations with a restriction factor, is proposed to account for the ISE differences between the two grains. Despite substantial twinning in the [0 0 1]-oriented grain at higher loads, the contribution of deformation twins to dislocation accumulation is negligible. The present work highlights the critical roles that partial dislocations play and how they influence the ISE in low stacking-fault energy alloys.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"192 ","pages":"Article 104428"},"PeriodicalIF":12.8000,"publicationDate":"2025-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Indentation size effect in a CoCrNi medium-entropy alloy: roles of partial dislocations and deformation twins\",\"authors\":\"Xuekun Shang , Zhiyuan Liang , Binbin He\",\"doi\":\"10.1016/j.ijplas.2025.104428\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>In this study, we investigated the indentation size effect (ISE) in a CoCrNi medium-entropy alloy using nanoindentation experiments and transmission electron microscopy (TEM) observations. Interestingly, the depth-hardness curves of two grains with different crystal orientations exhibit a crossover phenomenon together with orientation-dependent twinning behaviour. Comprehensive TEM characterization revealed that plastic deformation was accommodated by perfect dislocation slip in the [0 1 1]-oriented grains, whereas it involved dislocation slip, stacking faults, and deformation twins in the [0 0 1]-oriented grain. Partial dislocation slip was found to dominate in the [0 0 1]-oriented grain at very small depths, thereby suppressing dislocation motion and cross-slips, resulting in a higher dislocation density and increased hardness. A modified Nix-Gao model, incorporating partial dislocations with a restriction factor, is proposed to account for the ISE differences between the two grains. Despite substantial twinning in the [0 0 1]-oriented grain at higher loads, the contribution of deformation twins to dislocation accumulation is negligible. The present work highlights the critical roles that partial dislocations play and how they influence the ISE in low stacking-fault energy alloys.</div></div>\",\"PeriodicalId\":340,\"journal\":{\"name\":\"International Journal of Plasticity\",\"volume\":\"192 \",\"pages\":\"Article 104428\"},\"PeriodicalIF\":12.8000,\"publicationDate\":\"2025-07-20\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"International Journal of Plasticity\",\"FirstCategoryId\":\"88\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0749641925001871\",\"RegionNum\":1,\"RegionCategory\":\"材料科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"ENGINEERING, MECHANICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Plasticity","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0749641925001871","RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
Indentation size effect in a CoCrNi medium-entropy alloy: roles of partial dislocations and deformation twins
In this study, we investigated the indentation size effect (ISE) in a CoCrNi medium-entropy alloy using nanoindentation experiments and transmission electron microscopy (TEM) observations. Interestingly, the depth-hardness curves of two grains with different crystal orientations exhibit a crossover phenomenon together with orientation-dependent twinning behaviour. Comprehensive TEM characterization revealed that plastic deformation was accommodated by perfect dislocation slip in the [0 1 1]-oriented grains, whereas it involved dislocation slip, stacking faults, and deformation twins in the [0 0 1]-oriented grain. Partial dislocation slip was found to dominate in the [0 0 1]-oriented grain at very small depths, thereby suppressing dislocation motion and cross-slips, resulting in a higher dislocation density and increased hardness. A modified Nix-Gao model, incorporating partial dislocations with a restriction factor, is proposed to account for the ISE differences between the two grains. Despite substantial twinning in the [0 0 1]-oriented grain at higher loads, the contribution of deformation twins to dislocation accumulation is negligible. The present work highlights the critical roles that partial dislocations play and how they influence the ISE in low stacking-fault energy alloys.
期刊介绍:
International Journal of Plasticity aims to present original research encompassing all facets of plastic deformation, damage, and fracture behavior in both isotropic and anisotropic solids. This includes exploring the thermodynamics of plasticity and fracture, continuum theory, and macroscopic as well as microscopic phenomena.
Topics of interest span the plastic behavior of single crystals and polycrystalline metals, ceramics, rocks, soils, composites, nanocrystalline and microelectronics materials, shape memory alloys, ferroelectric ceramics, thin films, and polymers. Additionally, the journal covers plasticity aspects of failure and fracture mechanics. Contributions involving significant experimental, numerical, or theoretical advancements that enhance the understanding of the plastic behavior of solids are particularly valued. Papers addressing the modeling of finite nonlinear elastic deformation, bearing similarities to the modeling of plastic deformation, are also welcomed.