In a bid to improve the mechanical properties of high-entropy alloys, particularly their strain hardening capability, we adapted the time-proven concept of ‘twinning engineering’, developed in the context of TWIP steels, to this group of materials. The strategy chosen involved a two-step thermomechanical processing that consisted in low-temperature pre-straining and subsequent annealing. This approach was trialled on CoCrFeMnNi as an exemplary high-entropy alloy. The annealing conditions selected ensured that the deformation twins generated under low-temperature deformation were retained, whilst the dislocation density was recovered. The viability of this strategy was convincingly confirmed for room temperature deformation of the alloy. A constitutive model accounting for the effect of the pre-straining induced deformation twins was proposed. It was shown to provide a reliable description of the low-temperature and room-temperature deformation of CoCrFeMnNi.
{"title":"Twinning Engineering of High-Entropy Alloys: An Exercise in Process Optimization and Modeling","authors":"J. Moon, O. Bouaziz, Hyoung-Seop Kim, Y. Estrin","doi":"10.2139/ssrn.3787882","DOIUrl":"https://doi.org/10.2139/ssrn.3787882","url":null,"abstract":"In a bid to improve the mechanical properties of high-entropy alloys, particularly their strain hardening capability, we adapted the time-proven concept of ‘twinning engineering’, developed in the context of TWIP steels, to this group of materials. The strategy chosen involved a two-step thermomechanical processing that consisted in low-temperature pre-straining and subsequent annealing. This approach was trialled on CoCrFeMnNi as an exemplary high-entropy alloy. The annealing conditions selected ensured that the deformation twins generated under low-temperature deformation were retained, whilst the dislocation density was recovered. The viability of this strategy was convincingly confirmed for room temperature deformation of the alloy. A constitutive model accounting for the effect of the pre-straining induced deformation twins was proposed. It was shown to provide a reliable description of the low-temperature and room-temperature deformation of CoCrFeMnNi.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"470 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86723781","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}
Jean-Hughes Fournier-Lupien, C. Lacroix, J. Huh, J. Masse, J. Bellemare, F. Sirois
Abstract This paper presents extensive electrical, microstructural and chemical characterizations of HTS coated conductor samples in which an oxide layer (CeO x ) has been added between the superconductor (GdBaCuO) and the silver (Ag) layers, in an attempt to increase the interfacial resistance between these two conductive layers. This increase of interfacial resistance is required to realize the current flow diverter (CFD) architecture in HTS tapes. All samples in this paper have been characterized before and after performing an annealing in oxygen atmosphere. The purpose of the annealing was to reduce the interfacial resistance generated by the CeO x layer, in order to achieve a proper value for the CFD architecture. Samples with different thicknesses of CeO x , namely 0, 10, 35 and 100 nm, have been produced and characterized. The critical current and the critical temperature have been measured to determine the quality of the superconducting layers, while cross-section transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) have been used to monitor the impact of the annealing. The results show a clear degradation of the superconducting layer for samples with a thick layer ( ≥ 35 nm) of CeO x after annealing at 450 o C. According to the EDS results, a reduction of the amount of barium is observed in the superconducting layer, which could explain the observed reduction of the critical current.
{"title":"Effect of Annealing on HTS Tapes With a Cerium Oxide Layer Inserted Between the REBaCuO and Silver Layers","authors":"Jean-Hughes Fournier-Lupien, C. Lacroix, J. Huh, J. Masse, J. Bellemare, F. Sirois","doi":"10.2139/ssrn.3711250","DOIUrl":"https://doi.org/10.2139/ssrn.3711250","url":null,"abstract":"Abstract This paper presents extensive electrical, microstructural and chemical characterizations of HTS coated conductor samples in which an oxide layer (CeO x ) has been added between the superconductor (GdBaCuO) and the silver (Ag) layers, in an attempt to increase the interfacial resistance between these two conductive layers. This increase of interfacial resistance is required to realize the current flow diverter (CFD) architecture in HTS tapes. All samples in this paper have been characterized before and after performing an annealing in oxygen atmosphere. The purpose of the annealing was to reduce the interfacial resistance generated by the CeO x layer, in order to achieve a proper value for the CFD architecture. Samples with different thicknesses of CeO x , namely 0, 10, 35 and 100 nm, have been produced and characterized. The critical current and the critical temperature have been measured to determine the quality of the superconducting layers, while cross-section transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) have been used to monitor the impact of the annealing. The results show a clear degradation of the superconducting layer for samples with a thick layer ( ≥ 35 nm) of CeO x after annealing at 450 o C. According to the EDS results, a reduction of the amount of barium is observed in the superconducting layer, which could explain the observed reduction of the critical current.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"61 6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79769620","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 systematic study of friction stir welding in three precipitation hardened wrought Al alloys (2024-T351, 6061-T651, and 7075-T735) has been conducted. The material flow, microstructure evolution, defects and precipitates formation mechanisms, and mechanical properties for different tool rotation and traverse speeds have been systematically investigated for 15 mm-thick butt-welds of similar alloys plates. The nugget zones in all welds were determined to be formed by two material flows – shoulder-driven and pin-driven. The shoulder-driven flow at the top of the weld corresponds to bulk material transfer (i.e., bulk material flow), while the pin-driven flow occurs through a combination of layer-by-layer material transfer (i.e., layered extrusion flow, due to the pin’s extrusion effect) and bulk material flow. The relative volumes of the layered and bulk material flows are dependent on the material and processing parameters. Weld defects are formed when significant differences in flow stress between shoulder-driven and pin-driven flows exist, due to the inhomogeneous heat distribution across the large weld thickness. For materials with higher thermal conductivity, lower flow stresses and temperature gradients, as well as reduced heat inputs result in reduced defect formation. Different techniques, including TEM and DSC characterization, have been used to study the precipitation behavior in friction stir welds. Heterogeneity between the top and bottom regions of the nugget zone was observed. Increasing traverse speed improves the tensile strength and ductility of most studied alloys, and discussions on optimizing the resulting weld quality and mechanical properties using an integrated material flow-microstructure evolution understanding will be presented.
{"title":"Friction Stir Welding of Similar Aluminum Alloys Thick Plates: An Understanding of the Material Flow, Microstructure Evolution, and Mechanical Properties","authors":"Xiangbin Wang, D. Lados","doi":"10.2139/ssrn.3774580","DOIUrl":"https://doi.org/10.2139/ssrn.3774580","url":null,"abstract":"A systematic study of friction stir welding in three precipitation hardened wrought Al alloys (2024-T351, 6061-T651, and 7075-T735) has been conducted. The material flow, microstructure evolution, defects and precipitates formation mechanisms, and mechanical properties for different tool rotation and traverse speeds have been systematically investigated for 15 mm-thick butt-welds of similar alloys plates. The nugget zones in all welds were determined to be formed by two material flows – shoulder-driven and pin-driven. The shoulder-driven flow at the top of the weld corresponds to bulk material transfer (i.e., bulk material flow), while the pin-driven flow occurs through a combination of layer-by-layer material transfer (i.e., layered extrusion flow, due to the pin’s extrusion effect) and bulk material flow. The relative volumes of the layered and bulk material flows are dependent on the material and processing parameters. Weld defects are formed when significant differences in flow stress between shoulder-driven and pin-driven flows exist, due to the inhomogeneous heat distribution across the large weld thickness. For materials with higher thermal conductivity, lower flow stresses and temperature gradients, as well as reduced heat inputs result in reduced defect formation. Different techniques, including TEM and DSC characterization, have been used to study the precipitation behavior in friction stir welds. Heterogeneity between the top and bottom regions of the nugget zone was observed. Increasing traverse speed improves the tensile strength and ductility of most studied alloys, and discussions on optimizing the resulting weld quality and mechanical properties using an integrated material flow-microstructure evolution understanding will be presented.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86707941","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}
M. Pourgharibshahi, H. Saghafian, M. Divandari, Farrokh Golestannejad
Instrumented Constrained Rod Casting (CRC) method and the Controlled Diffusion Solidification (CDS) process were used to study the high susceptibility of the aluminum alloy AA 7068 to hot-tearing. A precise analysis of the measured hot-tearing curves is provided considering the casting design and different feeding mechanisms. Scanning Electron Microscopy was used to study the hot-tear surfaces. It was found that the solidification of the eutectic liquid at the film stage and the phenomenon of solid-feeding strongly affects the hot-tear formation. The early formation of an absorbed eutectic layer on the primary phase due to low rate of back-diffusion is proposed to explain the loss of ductility at the film stage. The layer can serve as an efficient substrate for the eutectic nucleation and growth, hence its formation can advance the eutectic solidification. The isolation of liquid eutectic by its partial solidification results in development of solid-feeding stresses breaking the solid eutectic and provide the required tearing initiators. By increasing the back-diffusion rate, the CDS process avoids formation of the adsorbed solid layer which postpones eutectic solidification and thereby mitigating the hot-tearing susceptibility.
{"title":"A Critical Conception of Hot-Tearing Susceptibility: How Controlled Diffusion Solidification Enables Shape-Casting with Wrought Aluminum Alloys","authors":"M. Pourgharibshahi, H. Saghafian, M. Divandari, Farrokh Golestannejad","doi":"10.2139/ssrn.3774574","DOIUrl":"https://doi.org/10.2139/ssrn.3774574","url":null,"abstract":"Instrumented Constrained Rod Casting (CRC) method and the Controlled Diffusion Solidification (CDS) process were used to study the high susceptibility of the aluminum alloy AA 7068 to hot-tearing. A precise analysis of the measured hot-tearing curves is provided considering the casting design and different feeding mechanisms. Scanning Electron Microscopy was used to study the hot-tear surfaces. It was found that the solidification of the eutectic liquid at the film stage and the phenomenon of solid-feeding strongly affects the hot-tear formation. The early formation of an absorbed eutectic layer on the primary phase due to low rate of back-diffusion is proposed to explain the loss of ductility at the film stage. The layer can serve as an efficient substrate for the eutectic nucleation and growth, hence its formation can advance the eutectic solidification. The isolation of liquid eutectic by its partial solidification results in development of solid-feeding stresses breaking the solid eutectic and provide the required tearing initiators. By increasing the back-diffusion rate, the CDS process avoids formation of the adsorbed solid layer which postpones eutectic solidification and thereby mitigating the hot-tearing susceptibility.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"84 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74191784","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}
Qiyang Tan, Z. Fan, Xiaoqi Tang, Yu Yin, Gan Li, Danni Huang, Jingqi Zhang, Yingang Liu, Feng Wang, Tao Wu, Xianliang Yang, Han Huang, Q. Zhu, Mingxing Zhang
Selective laser melting (SLM) has been successful in fabricating advanced engineering parts with high geometrical complexities. However, some metals or alloys with high strength, low weldability, and large freezing range, such as 7075 aluminium alloy, have low AM processability and are hard to be directly SLM-fabricated. Here, we proposed a novel strategy, combining substrate modification and inoculation treatment, to fabricate a crack-free and dense high-strength 7075 alloy using SLM at a broad processing window. Inoculation of the 7075 alloy powder with 1 wt.% Ti submicron particles substantially refine the Al grains, effectively increasing the cracking resistance. Furthermore, the SLM substrate was modified, which allows integration of thermal insulation materials, such as vermiculite, to the substrate. As a result, the melt pool cooling rate and thermal gradient during solidification were significantly reduced. This directly led to a reduction in thermal stress within the melt pool. With combination of the substrate modification and Ti inoculation, crack-free, fine-equiaxed microstructure was obtained in the SLM-fabricated 7075 alloy that has the mechanical properties comparable to its wrought counterpart. This strategy can be implemented to SLM of other engineering alloys with low AM processability, providing a foundation for broadening industrial applications of SLM.
{"title":"A Novel Strategy to Additively Manufacture 7075 Aluminium Alloy With Selective Laser Melting","authors":"Qiyang Tan, Z. Fan, Xiaoqi Tang, Yu Yin, Gan Li, Danni Huang, Jingqi Zhang, Yingang Liu, Feng Wang, Tao Wu, Xianliang Yang, Han Huang, Q. Zhu, Mingxing Zhang","doi":"10.2139/ssrn.3774509","DOIUrl":"https://doi.org/10.2139/ssrn.3774509","url":null,"abstract":"Selective laser melting (SLM) has been successful in fabricating advanced engineering parts with high geometrical complexities. However, some metals or alloys with high strength, low weldability, and large freezing range, such as 7075 aluminium alloy, have low AM processability and are hard to be directly SLM-fabricated. Here, we proposed a novel strategy, combining substrate modification and inoculation treatment, to fabricate a crack-free and dense high-strength 7075 alloy using SLM at a broad processing window. Inoculation of the 7075 alloy powder with 1 wt.% Ti submicron particles substantially refine the Al grains, effectively increasing the cracking resistance. Furthermore, the SLM substrate was modified, which allows integration of thermal insulation materials, such as vermiculite, to the substrate. As a result, the melt pool cooling rate and thermal gradient during solidification were significantly reduced. This directly led to a reduction in thermal stress within the melt pool. With combination of the substrate modification and Ti inoculation, crack-free, fine-equiaxed microstructure was obtained in the SLM-fabricated 7075 alloy that has the mechanical properties comparable to its wrought counterpart. This strategy can be implemented to SLM of other engineering alloys with low AM processability, providing a foundation for broadening industrial applications of SLM.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"146 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80516180","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}
Q. Lu, Y. Lv, Chi Zhang, Hong-bo Zhang, Wei Chen, Zhanyuan Xu, P. Feng, J. Fan
Titanium alloys are desirable for applications in advanced hypersonic aircraft engines and gas turbines, but currently few materials can satisfy the associated high temperature oxidation requirements. Herein, we designed and fabricated a Ti5Si3 reinforced Ti-4Mo composite with a two-scale network architecture by low energy milling and spark plasma sintering. It displays superior oxidation resistance at 800°C owing to the in-situ formation of a multi-component surface layer. This oxide layer has been revealed to have a dense grain size gradient structure that consists of an outer TiO2 oxide layer and an inner TiO2 and SiO2 mixed oxide layer with a core-shell structure, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti5Si3 reinforcements and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between oxide layer and matrix. This along with high adhesion confers excellent thermal cycling life with no cracking or spallation during long term oxidation. In this regard, the secure operating temperature can be increased to 800°C, which can provide a design pathway for a new family of titanium matrix composites for high-temperature applications.
{"title":"Highly Anti-Oxidized Ti-4Mo Alloy With Two-Scale Network Architectured Ti 5Si 3 Reinforcement","authors":"Q. Lu, Y. Lv, Chi Zhang, Hong-bo Zhang, Wei Chen, Zhanyuan Xu, P. Feng, J. Fan","doi":"10.2139/ssrn.3770981","DOIUrl":"https://doi.org/10.2139/ssrn.3770981","url":null,"abstract":"Titanium alloys are desirable for applications in advanced hypersonic aircraft engines and gas turbines, but currently few materials can satisfy the associated high temperature oxidation requirements. Herein, we designed and fabricated a Ti5Si3 reinforced Ti-4Mo composite with a two-scale network architecture by low energy milling and spark plasma sintering. It displays superior oxidation resistance at 800°C owing to the in-situ formation of a multi-component surface layer. This oxide layer has been revealed to have a dense grain size gradient structure that consists of an outer TiO2 oxide layer and an inner TiO2 and SiO2 mixed oxide layer with a core-shell structure, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti5Si3 reinforcements and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between oxide layer and matrix. This along with high adhesion confers excellent thermal cycling life with no cracking or spallation during long term oxidation. In this regard, the secure operating temperature can be increased to 800°C, which can provide a design pathway for a new family of titanium matrix composites for high-temperature applications.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76393371","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}
F. Fujie, Hongyu Peng, Tuerxun Ailihumaer, B. Raghothamachar, M. Dudley, S. Harada, M. Tagawa, T. Ujihara
The contrast features of synchrotron X-ray topographic images of screw-type basal plane dislocations (BPDs) in on-axis 4H-SiC wafers have been studied. Screw BPD images are categorized into two types: one exhibiting a white line bordered by black lines and the other a pure black line contrast. Similar images for off-axis specimens and the corresponding ray-tracing simulations demonstrate that these contrasts can be attributed to the depth of the screw BPDs below the crystal surface. The correlation of the contrast features between simulations and the screw BPD topography images can be used to estimate the depth.
{"title":"Synchrotron X-Ray Topographic Image Contrast Variation of BPDs Located at Different Depths Below the Crystal Surface in 4H-SiC","authors":"F. Fujie, Hongyu Peng, Tuerxun Ailihumaer, B. Raghothamachar, M. Dudley, S. Harada, M. Tagawa, T. Ujihara","doi":"10.2139/ssrn.3762210","DOIUrl":"https://doi.org/10.2139/ssrn.3762210","url":null,"abstract":"The contrast features of synchrotron X-ray topographic images of screw-type basal plane dislocations (BPDs) in on-axis 4H-SiC wafers have been studied. Screw BPD images are categorized into two types: one exhibiting a white line bordered by black lines and the other a pure black line contrast. Similar images for off-axis specimens and the corresponding ray-tracing simulations demonstrate that these contrasts can be attributed to the depth of the screw BPDs below the crystal surface. The correlation of the contrast features between simulations and the screw BPD topography images can be used to estimate the depth.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81279198","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}
Reduction of Co3O4/BaTiO3 in forming gas followed by sintering in flowing nitrogen with carbon as oxygen getter was applied for the syntheses of magnetoelectric 0-3 Cox/(BaTiO3)1-x composites (x = 0.1 – 0.8). Phase pure BaTiO3 and a mixture of hexagonal and cubic Co were obtained with void-free embedding of micrometer-sized ferromagnetic Co particles in the ferroelectric BaTiO3 matrix. No incorporation of Co in the BaTiO3 matrix occurred and the nominal Co contents agree well with the experimental ones derived from Rietveld refinements and magnetic measurements. A complex field dependence of the magnetoelectric coefficient (αME) was found with at least two local maxima/minima and a pronounced hysteresis when the magnetic field and the polarization are oriented perpendicular to each other. The sample Co0.5/(BaTiO3)0.5 exhibits the largest αME values. The low-temperature phase transitions of BaTiO3 (tetragonal → orthorhombic → rhombohedral) can be observed in the temperature dependence of αME. In contrast to other composites the integral of αME and the magnetostriction of (hexagonal) cobalt show a distinctively different magnetic field behavior, which might be due to the additional presence of the cubic Co modification.
{"title":"Magnetoelectric Behavior of 0-3 Co/BaTiO 3-Composites","authors":"Toni Buttlar, S. Ebbinghaus","doi":"10.2139/ssrn.3952390","DOIUrl":"https://doi.org/10.2139/ssrn.3952390","url":null,"abstract":"Reduction of Co3O4/BaTiO3 in forming gas followed by sintering in flowing nitrogen with carbon as oxygen getter was applied for the syntheses of magnetoelectric 0-3 Cox/(BaTiO3)1-x composites (x = 0.1 – 0.8). Phase pure BaTiO3 and a mixture of hexagonal and cubic Co were obtained with void-free embedding of micrometer-sized ferromagnetic Co particles in the ferroelectric BaTiO3 matrix. No incorporation of Co in the BaTiO3 matrix occurred and the nominal Co contents agree well with the experimental ones derived from Rietveld refinements and magnetic measurements. A complex field dependence of the magnetoelectric coefficient (αME) was found with at least two local maxima/minima and a pronounced hysteresis when the magnetic field and the polarization are oriented perpendicular to each other. The sample Co0.5/(BaTiO3)0.5 exhibits the largest αME values. The low-temperature phase transitions of BaTiO3 (tetragonal → orthorhombic → rhombohedral) can be observed in the temperature dependence of αME. In contrast to other composites the integral of αME and the magnetostriction of (hexagonal) cobalt show a distinctively different magnetic field behavior, which might be due to the additional presence of the cubic Co modification.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"89 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74841001","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}
Aging during cold rolling improves the final magnetic properties of conventionally processed grain oriented electrical steels (GOES). In order to determine the influence of aging on the evolution of microstructure and texture during recrystallization, identical hot rolled GOES sheets, were cold rolled with and without aging, and examined by large-area electron backscatter diffraction (EBSD) investigations. Local misorientations were determined from the EBSD maps with a noise-correction technique and the statistical relevance of the EBSD-based texture measurements was examined and confirmed by a new approach. The most important effect of aging was found to be a significant modification of the deformation and recrystallization behaviour of the α-fiber components. In fact, the aging treatment resulted in more shear banding during cold rolling, which is attributed to dislocation pinning by carbon atoms. The dislocation pinning furthermore leads to significantly reduced recovery during annealing, which finally results in a higher remaining driving force for recrystallization and more nucleation sites in the otherwise sluggishly recrystallizing α-fiber grains. As a result the grain size of the aged material is significantly reduced. We assume that this smaller grain size provides a higher driving force for the subsequent growth of the Goss grains and leads to improved magnetic properties of the final processed GOES, although these relations have not been investigated here. In contrast, the α*-fiber, which is often suggested to be of importance for optimized Goss texture formation, was not found to be affected significantly by the aging treatment.
{"title":"Unravelling the Role of Aging During Cold Rolling on the Primary Recrystallization of Grain-Oriented Electrical Steels Using a Robust EBSD-Based Analysis Approach","authors":"Ceren Yilmaz, M. Teodorescu, S. Zaefferer","doi":"10.2139/ssrn.3951051","DOIUrl":"https://doi.org/10.2139/ssrn.3951051","url":null,"abstract":"Aging during cold rolling improves the final magnetic properties of conventionally processed grain oriented electrical steels (GOES). In order to determine the influence of aging on the evolution of microstructure and texture during recrystallization, identical hot rolled GOES sheets, were cold rolled with and without aging, and examined by large-area electron backscatter diffraction (EBSD) investigations. Local misorientations were determined from the EBSD maps with a noise-correction technique and the statistical relevance of the EBSD-based texture measurements was examined and confirmed by a new approach. The most important effect of aging was found to be a significant modification of the deformation and recrystallization behaviour of the α-fiber components. In fact, the aging treatment resulted in more shear banding during cold rolling, which is attributed to dislocation pinning by carbon atoms. The dislocation pinning furthermore leads to significantly reduced recovery during annealing, which finally results in a higher remaining driving force for recrystallization and more nucleation sites in the otherwise sluggishly recrystallizing α-fiber grains. As a result the grain size of the aged material is significantly reduced. We assume that this smaller grain size provides a higher driving force for the subsequent growth of the Goss grains and leads to improved magnetic properties of the final processed GOES, although these relations have not been investigated here. In contrast, the α*-fiber, which is often suggested to be of importance for optimized Goss texture formation, was not found to be affected significantly by the aging treatment.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86528377","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}
Agricultural waste disposal is among the environmental problem in many countries. Finding economical uses for this waste by incorporating it in a product is the approach often used to overcome the environmental issue. Banana fibre and coconut coir are major agricultural waste products in Sri Lanka and fewer amounts of these are converted into usable products. Manufacturing cement-stabilized earth blocks incorporating these waste materials can reduce the environmental impact. The present study focuses on the post-peak behavior and durability of banana fibre and coconut coir-strengthened cement-stabilized earth blocks. Banana fibre and coconut coir reinforced cement-stabilized earth blocks are tested for compression, flexural bending, water absorption, sorptivity and resistance against chemicals, wet-dry weathering and freeze-thaw weathering. The banana fibre is shown better post-peak behavior in compression and coconut coir shown better post-peak behavior in flexural. Both fibre reinforcements improved the block’s durability against the acid attack, alkaline attack, wet-dry weathering and freeze-thaw weathering. Moreover, the specimen reinforced with coconut coir was found to exhibit better durability compared to the specimen reinforced with banana fibres.
{"title":"Mechanical Performance and Durability of Banana Fibre and Coconut Coir Reinforced Cement Stabilized Earth Blocks","authors":"Kirupairaja Thanushan, N. Sathiparan","doi":"10.2139/ssrn.3891469","DOIUrl":"https://doi.org/10.2139/ssrn.3891469","url":null,"abstract":"Agricultural waste disposal is among the environmental problem in many countries. Finding economical uses for this waste by incorporating it in a product is the approach often used to overcome the environmental issue. Banana fibre and coconut coir are major agricultural waste products in Sri Lanka and fewer amounts of these are converted into usable products. Manufacturing cement-stabilized earth blocks incorporating these waste materials can reduce the environmental impact. The present study focuses on the post-peak behavior and durability of banana fibre and coconut coir-strengthened cement-stabilized earth blocks. Banana fibre and coconut coir reinforced cement-stabilized earth blocks are tested for compression, flexural bending, water absorption, sorptivity and resistance against chemicals, wet-dry weathering and freeze-thaw weathering. The banana fibre is shown better post-peak behavior in compression and coconut coir shown better post-peak behavior in flexural. Both fibre reinforcements improved the block’s durability against the acid attack, alkaline attack, wet-dry weathering and freeze-thaw weathering. Moreover, the specimen reinforced with coconut coir was found to exhibit better durability compared to the specimen reinforced with banana fibres.","PeriodicalId":7755,"journal":{"name":"AMI: Acta Materialia","volume":"74 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83999430","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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