Ye Zhang, Dongyang Li, C. Du, Hao He, C. Shu, F. Luo, Song Li, Yimin Li, Zheyu He, Hao He, Xieyi Zhang
Carbon addition is effective to promote biodegradation of iron-based implanted materials. However, how to accelerate degradation without compromising the mechanical properties lacks a detailed composition designing strategy. In this study, impurity contents, microstructure evolution, mechanical properties and in vitro corrosion of Fe-35Mn-C alloys are investigated. It is found that (i) the oxygen impurity reduced rapidly and carbides gradually precipitated (C ≥ 0.53 wt.%) with increasing carbon content; (ii) the optimal mechanical properties (σs = 723 MPa, 𝜀 = 30%) were obtained in carbides-free region (C = 0.40 wt.%); (iii) corrosion rate still increased to 6.7 mm/a (3 days) gradually although there were no carbides. Through the calculation of stacking fault energy and EBSD analysis, it is found that the twin-induced plastic deformation (TWIP) mechanism caused by the appearance of {111} twins is the main reason for the substantial increase in strength and elongation. At the same time, accelerating degradation mechanism without carbide precipitates was hypothesized for the first time. It can be seen from the calculation of density functional theory that as the interstitial carbon content increases, the matrix tends to be unstable. Therefore, even if there is no carbide formation, the degradation rate of the matrix can also be increased accordingly. This provides a theoretical basis for carbon content control and design of iron-based degradable vascular stents
{"title":"Accelerating Corrosion and Improving Mechanical Properties by Heterogeneous Interstitial Carbon in Biodegradable Fe-Mn-C Alloys","authors":"Ye Zhang, Dongyang Li, C. Du, Hao He, C. Shu, F. Luo, Song Li, Yimin Li, Zheyu He, Hao He, Xieyi Zhang","doi":"10.2139/ssrn.3859737","DOIUrl":"https://doi.org/10.2139/ssrn.3859737","url":null,"abstract":"Carbon addition is effective to promote biodegradation of iron-based implanted materials. However, how to accelerate degradation without compromising the mechanical properties lacks a detailed composition designing strategy. In this study, impurity contents, microstructure evolution, mechanical properties and <i>in vitro</i> corrosion of Fe-35Mn-C alloys are investigated. It is found that (i) the oxygen impurity reduced rapidly and carbides gradually precipitated (C ≥ 0.53 wt.%) with increasing carbon content; (ii) the optimal mechanical properties (σ<sub>s</sub> = 723 MPa, 𝜀 = 30%) were obtained in carbides-free region (C = 0.40 wt.%); (iii) corrosion rate still increased to 6.7 mm/a (3 days) gradually although there were no carbides. Through the calculation of stacking fault energy and EBSD analysis, it is found that the twin-induced plastic deformation (TWIP) mechanism caused by the appearance of {111} twins is the main reason for the substantial increase in strength and elongation. At the same time, accelerating degradation mechanism without carbide precipitates was hypothesized for the first time. It can be seen from the calculation of density functional theory that as the interstitial carbon content increases, the matrix tends to be unstable. Therefore, even if there is no carbide formation, the degradation rate of the matrix can also be increased accordingly. This provides a theoretical basis for carbon content control and design of iron-based degradable vascular stents","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"21 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125696750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Bogdanoff, L. Lattanzi, M. Merlin, E. Ghassemali, S. Seifeddine
The effect of copper (Cu) addition up to 3.2 wt.% on crack initiation and propagation in an Al-Si-Mg cast alloy was investigated using in-situ cyclic testing in the as-cast condition. A novel combination of digital image correlation, electron backscatter diffraction, and scanning electron microscopy was used to investigate crack initiation and propagation behaviour during in-situ cyclic testing. The results showed that Cu-rich intermetallic compounds with the addition of Cu up to 1.5 wt.% do not affect the fatigue behaviour of these alloys, and that crack propagation in these cases is trans-granular and trans-dendritic. However, increasing the concentration of the Cu retained in the primary α-Al matrix in solid solution and Cu-containing precipitates delayed crack propagation during cyclic testing. The results showed that strain accumulation was highest at the grain boundaries; however, the crack preferred to propagate along or across primary α-Al dendrites due to the relatively lower mechanical strength of the matrix compared to the eutectic and intermetallic phases. Moreover, the addition of Cu of more than 3.0 wt.% to Al-Si-Mg alloys changes the fatigue behaviour such that an almost static failure occurs, with limited crack propagation.
{"title":"The Influence of Copper Addition on Crack Initiation and Propagation in an Al-Si-Mg Alloy During Cyclic Testing","authors":"T. Bogdanoff, L. Lattanzi, M. Merlin, E. Ghassemali, S. Seifeddine","doi":"10.2139/ssrn.3600185","DOIUrl":"https://doi.org/10.2139/ssrn.3600185","url":null,"abstract":"The effect of copper (Cu) addition up to 3.2 wt.% on crack initiation and propagation in an Al-Si-Mg cast alloy was investigated using in-situ cyclic testing in the as-cast condition. A novel combination of digital image correlation, electron backscatter diffraction, and scanning electron microscopy was used to investigate crack initiation and propagation behaviour during in-situ cyclic testing. The results showed that Cu-rich intermetallic compounds with the addition of Cu up to 1.5 wt.% do not affect the fatigue behaviour of these alloys, and that crack propagation in these cases is trans-granular and trans-dendritic. However, increasing the concentration of the Cu retained in the primary α-Al matrix in solid solution and Cu-containing precipitates delayed crack propagation during cyclic testing. The results showed that strain accumulation was highest at the grain boundaries; however, the crack preferred to propagate along or across primary α-Al dendrites due to the relatively lower mechanical strength of the matrix compared to the eutectic and intermetallic phases. Moreover, the addition of Cu of more than 3.0 wt.% to Al-Si-Mg alloys changes the fatigue behaviour such that an almost static failure occurs, with limited crack propagation.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133681961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Balan, M. Perez, T. Chaise, S. Cazottes, D. Bardel, F. Corpace, F. Pichot, A. Deschamps, F. De Geuser, D. Nélias
This paper presents a coupled approach able to describe γ'' precipitation evolution and associated yield strength after various thermal treatments in inconel 718 alloy. The precipitation state is modeled via the implementation of classical nucleation and growth theories for plate-shaped particles. The precipitation model is validated through small-angle neutron scattering and transmission electron microscopy experiments. The precipitation size distribution serves as an input parameter to model the yield strength using a micromechanical model based on shear and bypass mechanisms accounting for the particular shapes of the precipitates. Results are in good agreement with measured yield stresses for various precipitation states. A complete simulated TTT diagram of the γ'' phase with the associated yield strength is proposed. The coupled model is finally applied to a series of non-isothermal treatments representative of welding (or additive manufacturing) from the peak aged state.
{"title":"Precipitation of γ\" In Inconel 718 Alloy From Microstructure to Mechanical Properties","authors":"A. Balan, M. Perez, T. Chaise, S. Cazottes, D. Bardel, F. Corpace, F. Pichot, A. Deschamps, F. De Geuser, D. Nélias","doi":"10.2139/ssrn.3859738","DOIUrl":"https://doi.org/10.2139/ssrn.3859738","url":null,"abstract":"This paper presents a coupled approach able to describe γ'' precipitation evolution and associated yield strength after various thermal treatments in inconel 718 alloy. The precipitation state is modeled via the implementation of classical nucleation and growth theories for plate-shaped particles. The precipitation model is validated through small-angle neutron scattering and transmission electron microscopy experiments. The precipitation size distribution serves as an input parameter to model the yield strength using a micromechanical model based on shear and bypass mechanisms accounting for the particular shapes of the precipitates. Results are in good agreement with measured yield stresses for various precipitation states. A complete simulated TTT diagram of the γ'' phase with the associated yield strength is proposed. The coupled model is finally applied to a series of non-isothermal treatments representative of welding (or additive manufacturing) from the peak aged state.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133897195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Domain walls are of increasing interest in ferroelectrics because of their unique properties and potential applications in future nanoelectronics. However, the thickness of ferroelastic domain walls remains elusive due to the challenges in experimental characterization. Here, we determine the atomic structure of ferroelastic domain walls and precisely measure the polarization and domain wall thickness at picometer scale using annular bright field imaging in an aberration-corrected scanning transmission electron microscope. We find that the domain wall thickness in PbZr0.2Ti0.8O3 and PbTiO3 thin films is typically about one-unit cell, across which the oxygen octahedron distortion behavior is in excellent agreement with first principles calculations. Remarkably, wider domain walls about two-unit cells in thickness are also observed for those domains walls are coupled with dislocations and underwent a compressive strain. These results suggest that the thickness of ferroelastic domain walls highly depends on their atomic environments. This study can help us to understand the past debatable experimental results and provide further insights into control of domain walls via strain engineering for their possible applications in nanoelectronics.
{"title":"Atomic-Environment-Dependent Thickness of Ferroelastic Domain Walls","authors":"Mingqiang Li, Xiaomei Li, Yuehui Li, Heng-Jui Liu, Y. Chu, Peng Gao","doi":"10.2139/ssrn.3478000","DOIUrl":"https://doi.org/10.2139/ssrn.3478000","url":null,"abstract":"Domain walls are of increasing interest in ferroelectrics because of their unique properties and potential applications in future nanoelectronics. However, the thickness of ferroelastic domain walls remains elusive due to the challenges in experimental characterization. Here, we determine the atomic structure of ferroelastic domain walls and precisely measure the polarization and domain wall thickness at picometer scale using annular bright field imaging in an aberration-corrected scanning transmission electron microscope. We find that the domain wall thickness in PbZr<sub>0.2</sub>Ti<sub>0.8</sub>O<sub>3</sub> and PbTiO<sub>3</sub> thin films is typically about one-unit cell, across which the oxygen octahedron distortion behavior is in excellent agreement with first principles calculations. Remarkably, wider domain walls about two-unit cells in thickness are also observed for those domains walls are coupled with dislocations and underwent a compressive strain. These results suggest that the thickness of ferroelastic domain walls highly depends on their atomic environments. This study can help us to understand the past debatable experimental results and provide further insights into control of domain walls via strain engineering for their possible applications in nanoelectronics.","PeriodicalId":180833,"journal":{"name":"Mechanical Properties & Deformation of Materials eJournal","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129198395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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