William Bodel, P. Martinuzzi, B. Davies, Alan Steer, T. Lowe, P. Mummery
Abstract Keyway root cracking and radiolytic weight loss in graphite moderated nuclear reactors may limit future successful operation of the civil nuclear fleet. A novel means of initiating fracture using internally generated stresses has been developed, which uses bromine intercalation to induce fracture in small graphite samples. Successful crack initiation and propagation has been achieved in 1:10 scale reactor components. In situ X-ray Computed Tomography during bromination has enabled observations of failure in real time, allowing the role of microstructure during fracture and weight loss to be determined. Crack paths predicted by models have been assessed.
{"title":"Mimicking Irradiation-Induced Cracking of Nuclear Graphite Using Bromine Intercalation","authors":"William Bodel, P. Martinuzzi, B. Davies, Alan Steer, T. Lowe, P. Mummery","doi":"10.2139/ssrn.3742927","DOIUrl":"https://doi.org/10.2139/ssrn.3742927","url":null,"abstract":"Abstract Keyway root cracking and radiolytic weight loss in graphite moderated nuclear reactors may limit future successful operation of the civil nuclear fleet. A novel means of initiating fracture using internally generated stresses has been developed, which uses bromine intercalation to induce fracture in small graphite samples. Successful crack initiation and propagation has been achieved in 1:10 scale reactor components. In situ X-ray Computed Tomography during bromination has enabled observations of failure in real time, allowing the role of microstructure during fracture and weight loss to be determined. Crack paths predicted by models have been assessed.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72867410","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}
Abstract Titanium/steel laminated composites form a tooth-like interface which is subjected to alternating shear/normal stresses during cold roll bonding process. Interfacial shear stress promotes atomic diffusion and gives birth to nano-grains, resulting in an interface mixed with nanocrystalline and amorphous region. Interfacial normal stress introduces high dislocation density, resulting in an interfacial transition zone.
{"title":"Stress-Induced Alternating Microstructures of Titanium/Steel Bonding Interface","authors":"Yu-Liang Bai, Xue-Feng Liu, Zhang-Zhi Shi","doi":"10.2139/ssrn.3721833","DOIUrl":"https://doi.org/10.2139/ssrn.3721833","url":null,"abstract":"Abstract Titanium/steel laminated composites form a tooth-like interface which is subjected to alternating shear/normal stresses during cold roll bonding process. Interfacial shear stress promotes atomic diffusion and gives birth to nano-grains, resulting in an interface mixed with nanocrystalline and amorphous region. Interfacial normal stress introduces high dislocation density, resulting in an interfacial transition zone.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78306041","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}
Interactions of alloying elements (Si,Mg,Mn,Zr,Zn) and vacancies with coherent interfaces of θ′ phase in Al-based alloys have been systematically studied by means of ab initio calculations. The interface structure with a filled interfacial Cu layer is calculated to be lower in energy than the structure with a half-filled Cu layer (by 0.1 eV per structural vacancy), which implies that a temperature-induced reconstruction of the interface may take place. The presence of vacancies in the interfacial Cu layer structure plays a crucial role in the interaction of solutes with a coherent θ′ phase interface. The solute–interface interaction energies are calculated to be much weaker for elements having closed (Cu,Zn) or empty (Mg,Si) d-electron shells than for d-transition metals (Mn,Zr). To clarify the roles of alloying elements and interface structure in the stability of θ′ phase precipitates, we analyze the solute–interface interactions in terms of electronic-structure and atomic-size contributions to interatomic bonding.
{"title":"Segregation of Alloying Elements to Stabilize Teta Prime Phase Interfaces in Al-Cu Based Alloys","authors":"M. Petrik, Y. Gornostyrev, P. Korzhavyi","doi":"10.2139/ssrn.3718100","DOIUrl":"https://doi.org/10.2139/ssrn.3718100","url":null,"abstract":"Interactions of alloying elements (Si,Mg,Mn,Zr,Zn) and vacancies with coherent interfaces of θ′ phase in Al-based alloys have been systematically studied by means of ab initio calculations. The interface structure with a filled interfacial Cu layer is calculated to be lower in energy than the structure with a half-filled Cu layer (by 0.1 eV per structural vacancy), which implies that a temperature-induced reconstruction of the interface may take place. The presence of vacancies in the interfacial Cu layer structure plays a crucial role in the interaction of solutes with a coherent θ′ phase interface. The solute–interface interaction energies are calculated to be much weaker for elements having closed (Cu,Zn) or empty (Mg,Si) d-electron shells than for d-transition metals (Mn,Zr). To clarify the roles of alloying elements and interface structure in the stability of θ′ phase precipitates, we analyze the solute–interface interactions in terms of electronic-structure and atomic-size contributions to interatomic bonding.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75088402","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}
Abstract Static strain aging behavior of cold-rolled 16Cr-5Ni supermartensitic stainless steel was investigated after it had been aged for 30 min at 400°C. In uniaxial tensile tests of 20% cold-rolled specimens, increase of yield strength to ~300 MPa and decrease of strain hardening rate were observed in the aged specimen, compared to the as-rolled specimen. In interrupted tensile tests, delayed martensitic transformation was observed in the aged specimen. Dilatometry analysis detected volume shrinkage during the 30 min holding period at 400°C indicating partitioning of carbon (C) from α’ martensite to austenite. The clustering of C in α’ martensite was confirmed by impulse internal friction technique with observation of Cottrell atmosphere formation. 3D atom probe tomography analysis revealed partitioning of C atoms into austenite and clustering of C atoms in the α’ martensite. The remarkable increase of yield strength was attributed to redistribution of C atoms during the aging treatment.
{"title":"C Clustering and Partitioning by Static Strain Aging in Cold-Rolled 16cr-5ni Supermartensitic Stainless Steel","authors":"Hojun Gwon, Sung-Ho Kim, J. Jeon, Sung-Joon Kim","doi":"10.2139/ssrn.3692029","DOIUrl":"https://doi.org/10.2139/ssrn.3692029","url":null,"abstract":"Abstract Static strain aging behavior of cold-rolled 16Cr-5Ni supermartensitic stainless steel was investigated after it had been aged for 30 min at 400°C. In uniaxial tensile tests of 20% cold-rolled specimens, increase of yield strength to ~300 MPa and decrease of strain hardening rate were observed in the aged specimen, compared to the as-rolled specimen. In interrupted tensile tests, delayed martensitic transformation was observed in the aged specimen. Dilatometry analysis detected volume shrinkage during the 30 min holding period at 400°C indicating partitioning of carbon (C) from α’ martensite to austenite. The clustering of C in α’ martensite was confirmed by impulse internal friction technique with observation of Cottrell atmosphere formation. 3D atom probe tomography analysis revealed partitioning of C atoms into austenite and clustering of C atoms in the α’ martensite. The remarkable increase of yield strength was attributed to redistribution of C atoms during the aging treatment.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"128 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88709748","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. Matsumae, Y. Kurashima, H. Takagi, H. Umezawa, E. Higurashi
Abstract Direct bonding of a diamond (100) substrate and a Si wafer was achieved at 250°C under atmospheric conditions. Prior to the bonding process, the diamond substrate was treated with H2SO4/H2O2 and NH3/H2O2 mixtures, whereas the Si wafer was irradiated using oxygen plasma. By applying the pressure during the annealing process, the substrates were entirely bonded, except for the contaminated areas. The bonded specimen was fractured when a shear force of 1.7 MPa was applied. The electron microscopic observation indicated that the diamond and Si substrates were atomically bonded through a 3-nm-thick SiO2 layer without significant loss of diamond crystallinity. The integration of diamond (100) substrates on an Si wafer would contribute to the fabrication of future diamond devices.
{"title":"Low-Temperature Direct Bonding of Diamond (100) Substrate on Si Wafer Under Atmospheric Conditions","authors":"T. Matsumae, Y. Kurashima, H. Takagi, H. Umezawa, E. Higurashi","doi":"10.2139/ssrn.3674205","DOIUrl":"https://doi.org/10.2139/ssrn.3674205","url":null,"abstract":"Abstract Direct bonding of a diamond (100) substrate and a Si wafer was achieved at 250°C under atmospheric conditions. Prior to the bonding process, the diamond substrate was treated with H2SO4/H2O2 and NH3/H2O2 mixtures, whereas the Si wafer was irradiated using oxygen plasma. By applying the pressure during the annealing process, the substrates were entirely bonded, except for the contaminated areas. The bonded specimen was fractured when a shear force of 1.7 MPa was applied. The electron microscopic observation indicated that the diamond and Si substrates were atomically bonded through a 3-nm-thick SiO2 layer without significant loss of diamond crystallinity. The integration of diamond (100) substrates on an Si wafer would contribute to the fabrication of future diamond devices.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76043867","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. Cochell, R. Unocic, J. Graña-Otero, Alexandre Martin
Thermal protection systems (TPS) are used to protect spacecraft payloads during the extreme conditions of atmospheric entry. The backbone of the composite TPS material used in the NASA Stardust Sample Return Capsule and the Mars 2020 mission is carbon fiber, which oxidizes at these temperatures and atmospheric conditions. This study presents the direct observation of carbon oxidation using in situ Scanning Transmission Electron Microscopy (STEM). A thin section of a commercially-available carbon fiber material containing multiple carbon structures was examined by STEM in a closed-environmental cell in which temperature was raised from 25 to 1050àC under a steady flow of air. Results show that the random polycrystalline carbon structure oxidized more uniformly and rapidly than the single crystallite region, which oxidized more anisotropically. These findings are the first to directly observe the structural dependence of carbon oxidation rates at these length-scales while also giving important insight into the onset of pitting at various active surface sites, important pieces in fundamentally understanding of carbon oxidation.
{"title":"Nanoscale Oxidation Behavior of Carbon Fibers Revealed with in situ Gas Cell STEM","authors":"T. Cochell, R. Unocic, J. Graña-Otero, Alexandre Martin","doi":"10.2139/ssrn.3746790","DOIUrl":"https://doi.org/10.2139/ssrn.3746790","url":null,"abstract":"Thermal protection systems (TPS) are used to protect spacecraft payloads during the extreme conditions of atmospheric entry. The backbone of the composite TPS material used in the NASA Stardust Sample Return Capsule and the Mars 2020 mission is carbon fiber, which oxidizes at these temperatures and atmospheric conditions. This study presents the direct observation of carbon oxidation using in situ Scanning Transmission Electron Microscopy (STEM). A thin section of a commercially-available carbon fiber material containing multiple carbon structures was examined by STEM in a closed-environmental cell in which temperature was raised from 25 to 1050àC under a steady flow of air. Results show that the random polycrystalline carbon structure oxidized more uniformly and rapidly than the single crystallite region, which oxidized more anisotropically. These findings are the first to directly observe the structural dependence of carbon oxidation rates at these length-scales while also giving important insight into the onset of pitting at various active surface sites, important pieces in fundamentally understanding of carbon oxidation.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82937392","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}
B. Kong, J. Shin, Gokul Obulan Subramanian, Junjie Chen, C. Jang, Ye-Eun Na, D. Jang, H. Lee, Jun-seog Yang
Abstract Nanopillar compression tests were applied on δ-ferrites in austenitic stainless steel welds to measure the thermal ageing activation energy caused by spinodal decomposition. Welds of an austenitic stainless steel were thermally aged at 343, 375, and 400 oC for up to 20,000 h. To avoid the interference of surrounding austenite matrix on embrittlement measurement, austenite matrix was selectively dissolved before the nanopillar fabrication. Using the yield stress changes measured by nanopillar compression tests, the thermal ageing activation energy of δ-ferrite was estimated as 154 KJ/mol, which was compared with literature results and the reasons of discrepancy were discussed.
{"title":"Evaluation of Thermal Ageing Activation Energy of Δ-Ferrite in an Austenitic Stainless Steel Weld Using Nanopillar Compression Test","authors":"B. Kong, J. Shin, Gokul Obulan Subramanian, Junjie Chen, C. Jang, Ye-Eun Na, D. Jang, H. Lee, Jun-seog Yang","doi":"10.2139/ssrn.3552441","DOIUrl":"https://doi.org/10.2139/ssrn.3552441","url":null,"abstract":"Abstract Nanopillar compression tests were applied on δ-ferrites in austenitic stainless steel welds to measure the thermal ageing activation energy caused by spinodal decomposition. Welds of an austenitic stainless steel were thermally aged at 343, 375, and 400 oC for up to 20,000 h. To avoid the interference of surrounding austenite matrix on embrittlement measurement, austenite matrix was selectively dissolved before the nanopillar fabrication. Using the yield stress changes measured by nanopillar compression tests, the thermal ageing activation energy of δ-ferrite was estimated as 154 KJ/mol, which was compared with literature results and the reasons of discrepancy were discussed.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87061056","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}
C. L. Xu, T. Andriollo, Yubin Zhang, J. C. Hernando, J. Hattel, N. Tiedje
Abstract Strain partitioning between first-to-solidify (FTS) and last-to-solidify (LTS) regions upon tensile loading of ductile iron was investigated by combining in-situ X-ray tomography with digital volume correlation and postmortem metallographic examinations. The results indicate that the plastic shear bands form mainly by linking graphite particles contained in the same FTS region. A special distance function is introduced to show that this is due to the lower strength of the FTS regions compared to the LTS regions, but also to the higher stress concentration associated with the particles. The methodology is general and therefore extendable to material systems containing similar microstructural heterogeneities.
{"title":"Micromechanical Impact of Solidification Regions in Ductile Iron Revealed Via a 3D Strain Partitioning Analysis Method","authors":"C. L. Xu, T. Andriollo, Yubin Zhang, J. C. Hernando, J. Hattel, N. Tiedje","doi":"10.2139/ssrn.3485109","DOIUrl":"https://doi.org/10.2139/ssrn.3485109","url":null,"abstract":"Abstract Strain partitioning between first-to-solidify (FTS) and last-to-solidify (LTS) regions upon tensile loading of ductile iron was investigated by combining in-situ X-ray tomography with digital volume correlation and postmortem metallographic examinations. The results indicate that the plastic shear bands form mainly by linking graphite particles contained in the same FTS region. A special distance function is introduced to show that this is due to the lower strength of the FTS regions compared to the LTS regions, but also to the higher stress concentration associated with the particles. The methodology is general and therefore extendable to material systems containing similar microstructural heterogeneities.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88782933","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}
Fei Guo, Zhifeng Shi, Bo Yang, Yaping Liu, Shifeng Zhao
Flexible lead-free Na0.5Bi0.5TiO3-EuTiO3 solid solution film capacitors were fabricated. The recoverable energy storage density and energy storage efficiency reach 65.4 J/cm3 and 52 %, respectively, due to the great insulation characteristic and relaxor behaviors. And the energy storage performances for the flexible solid solution films show excellent stabilities on temperature, frequency and bending endurance, especially, with bending endurance stability over 105 cycles. The flexoelectric effect also contributes to the regulation on energy storage performances by bending the flexible films. This work provides an candidate for the flexible film capacitors with giant application potentials in wearable energy storage devices.
{"title":"Flexible Lead-Free Na0.5bi0.5tio3-Eutio3 Solid Solution Film Capacitors with Stable and Superior Energy Storage Performances","authors":"Fei Guo, Zhifeng Shi, Bo Yang, Yaping Liu, Shifeng Zhao","doi":"10.2139/ssrn.3538823","DOIUrl":"https://doi.org/10.2139/ssrn.3538823","url":null,"abstract":"Flexible lead-free Na0.5Bi0.5TiO3-EuTiO3 solid solution film capacitors were fabricated. The recoverable energy storage density and energy storage efficiency reach 65.4 J/cm3 and 52 %, respectively, due to the great insulation characteristic and relaxor behaviors. And the energy storage performances for the flexible solid solution films show excellent stabilities on temperature, frequency and bending endurance, especially, with bending endurance stability over 105 cycles. The flexoelectric effect also contributes to the regulation on energy storage performances by bending the flexible films. This work provides an candidate for the flexible film capacitors with giant application potentials in wearable energy storage devices.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84790039","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}
High-temperature micro-fracture tests of an industrial grade W-1%Ta alloy were performed from room temperature up to 700 °C, using chevron-notched micro-cantilevers. A gradual increase of conditional fracture toughness (KQc) was measured with increasing temperature, and a microscale brittle-to-ductile transition temperature was found at ~600 °C. This is slightly higher than macroscopic four-point bending tests from the same material (~400 °C), and contradicts most literatures for pure tungsten that shows a significant lower micro-BDTT. The results suggested that dislocation motion should be independent of the specimen size. It is concluded that the higher micro-BDTT is due to tantalum in this alloy.
{"title":"Measuring the Brittle-to-Ductile Transition Temperature of Tungsten-Tantalum Alloy Using Chevron-Notched Micro-Cantilevers","authors":"B. Li, T. Marrow, David J Armstrong","doi":"10.2139/ssrn.3513127","DOIUrl":"https://doi.org/10.2139/ssrn.3513127","url":null,"abstract":"High-temperature micro-fracture tests of an industrial grade W-1%Ta alloy were performed from room temperature up to 700 °C, using chevron-notched micro-cantilevers. A gradual increase of conditional fracture toughness (KQc) was measured with increasing temperature, and a microscale brittle-to-ductile transition temperature was found at ~600 °C. This is slightly higher than macroscopic four-point bending tests from the same material (~400 °C), and contradicts most literatures for pure tungsten that shows a significant lower micro-BDTT. The results suggested that dislocation motion should be independent of the specimen size. It is concluded that the higher micro-BDTT is due to tantalum in this alloy.","PeriodicalId":7765,"journal":{"name":"AMI: Scripta Materialia","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90969484","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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