Pub Date : 2024-11-08DOI: 10.1016/j.matchar.2024.114540
Bo Yang , Baoxi Liu , Zhichao Luo , Hui Yu , Fuxing Yin
In this paper, the microstructure evolution and mechanical properties of low carbon steels during direct quenched and rolling followed by water-cooled processes were studied. Two experimental steels, which were directly quenched at 900 °C (Q900) and 1000 °C (Q1000), were compared with steels that were water-cooled after rolling at the same temperatures (R900 and R1000). Microstructural analyses using EBSD and TEM revealed that rolling reduced the size of prior austenite grains (PAGs), resulting in an average width of 3.6 μm, which influenced grain boundary distributions and variant selection. The best combination of strength, ductility and toughness was obtained in R900 steel, including tensile (with the yield strength of 1304 MPa, the total elongation of 22.95 %), Charpy impact (with the impact energy at 20 °C is 182 J), and fracture toughness evaluations (with the is 326.28 KJ/m2), this demonstrates that R900 steel exhibited significantly enhanced strength and ductility compared to Q900 steel. Moreover, EBSD analysis of crack propagation paths highlighted the role of high-angle grain boundaries (HAGBs) in enhancing fracture toughness by deflecting cracks. These findings underscore the critical role of PAGs size in tailoring microstructures to achieve superior mechanical properties in low carbon martensitic steels, offering insights for advanced material design and application in demanding structural and industrial contexts.
Keyworks.
low-carbon martensitic steel; strength and toughness; martensitic transformation; ductile-to-brittle transition phenomenon; selection of martensitic variants.
{"title":"Design and control the selection of martensitic variant to simultaneously improve strength and toughness of low-carbon martensitic steel","authors":"Bo Yang , Baoxi Liu , Zhichao Luo , Hui Yu , Fuxing Yin","doi":"10.1016/j.matchar.2024.114540","DOIUrl":"10.1016/j.matchar.2024.114540","url":null,"abstract":"<div><div>In this paper, the microstructure evolution and mechanical properties of low carbon steels during direct quenched and rolling followed by water-cooled processes were studied. Two experimental steels, which were directly quenched at 900 °C (Q900) and 1000 °C (Q1000), were compared with steels that were water-cooled after rolling at the same temperatures (R900 and R1000). Microstructural analyses using EBSD and TEM revealed that rolling reduced the size of prior austenite grains (PAGs), resulting in an average width of 3.6 μm, which influenced grain boundary distributions and variant selection. The best combination of strength, ductility and toughness was obtained in R900 steel, including tensile (with the yield strength of 1304 MPa, the total elongation of 22.95 %), Charpy impact (with the impact energy at 20 °C is 182 J), and fracture toughness evaluations (with the <span><math><msub><mi>J</mi><mrow><mn>1</mn><mi>c</mi></mrow></msub></math></span> is 326.28 KJ/m<sup>2</sup>), this demonstrates that R900 steel exhibited significantly enhanced strength and ductility compared to Q900 steel. Moreover, EBSD analysis of crack propagation paths highlighted the role of high-angle grain boundaries (HAGBs) in enhancing fracture toughness by deflecting cracks. These findings underscore the critical role of PAGs size in tailoring microstructures to achieve superior mechanical properties in low carbon martensitic steels, offering insights for advanced material design and application in demanding structural and industrial contexts.</div><div><strong>Keyworks.</strong></div><div>low-carbon martensitic steel; strength and toughness; martensitic transformation; ductile-to-brittle transition phenomenon; selection of martensitic variants.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114540"},"PeriodicalIF":4.8,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-08DOI: 10.1016/j.matchar.2024.114523
Shuanglan Lin , Lei Xu , Zhixing Guo , Dingcheng Zhang , Pangwei Zeng , Yuexin Tang , Hongliang Pei
Metallographic analysis is one of the most commonly used techniques by materials scientists for studying metal materials. The deep learning methods, which have been widely applied in metallographic images analysis, demonstrate excellent performance in this task. However, the optimization of deep learning models often relies on a substantial amount of accurately labeled samples for effective supervision. To address this issue, this paper proposes a novel automatic annotation method based on brightness and spatial distribution which is suitable for deep learning-based segmentation of optical dual-phase metallographic microstructure. The proposed automatic annotated method includes the superpixel segmentation, principal feature extraction, and clustering algorithm therefore it is referred as the superpixel-based principal feature clustering annotation (SPFCA) method. SPFCA employs discriminative criteria similar to those used by metallurgists to differentiate between metallographic structures. Furthermore, it can mitigate the occasional errors inherent in manual annotation, leading to improved performance compared to models trained with expert annotations. Experimental validation was conducted using four self-built datasets with different image qualities to test the performance of models from different perspective. Initially, hyperparameter optimization for the SPFCA method tailored to our dataset was performed. Subsequently, SPFCA was utilized to guide the optimization of the convolutional neural network employed for segmentation. The results demonstrate that the segmentation model optimized with SPFCA guidance achieved an F1 score of 0.9226 in the single dataset without the need for manual labeling, surpassing the segmentation models optimized with expert annotations.
{"title":"Superpixel-based principal feature clustering annotation method for dual-phase microstructure segmentation","authors":"Shuanglan Lin , Lei Xu , Zhixing Guo , Dingcheng Zhang , Pangwei Zeng , Yuexin Tang , Hongliang Pei","doi":"10.1016/j.matchar.2024.114523","DOIUrl":"10.1016/j.matchar.2024.114523","url":null,"abstract":"<div><div>Metallographic analysis is one of the most commonly used techniques by materials scientists for studying metal materials. The deep learning methods, which have been widely applied in metallographic images analysis, demonstrate excellent performance in this task. However, the optimization of deep learning models often relies on a substantial amount of accurately labeled samples for effective supervision. To address this issue, this paper proposes a novel automatic annotation method based on brightness and spatial distribution which is suitable for deep learning-based segmentation of optical dual-phase metallographic microstructure. The proposed automatic annotated method includes the superpixel segmentation, principal feature extraction, and clustering algorithm therefore it is referred as the superpixel-based principal feature clustering annotation (SPFCA) method. SPFCA employs discriminative criteria similar to those used by metallurgists to differentiate between metallographic structures. Furthermore, it can mitigate the occasional errors inherent in manual annotation, leading to improved performance compared to models trained with expert annotations. Experimental validation was conducted using four self-built datasets with different image qualities to test the performance of models from different perspective. Initially, hyperparameter optimization for the SPFCA method tailored to our dataset was performed. Subsequently, SPFCA was utilized to guide the optimization of the convolutional neural network employed for segmentation. The results demonstrate that the segmentation model optimized with SPFCA guidance achieved an F1 score of 0.9226 in the single dataset without the need for manual labeling, surpassing the segmentation models optimized with expert annotations.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114523"},"PeriodicalIF":4.8,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.matchar.2024.114517
Sen Du , Mingtao Wang , Shengen Zhang , Zhengfeng Lv , Zhiyuan Xu , Chen Liu , Jingtao Wang , Jun Liu , Bo Liu
The remelted aluminum scrap exhibits elevated inclusion levels, a condition inadequately addressed by contemporary refining methodologies, particularly with respect to the extraction of diminutive inclusions. The objective of this investigation is to delineate the repercussions of micron-scale inclusions on the corrosion behavior of recycled Al-Zn-Mg-Cu alloy sheets. Aluminum melts, varying in cleanliness, were reprocessed into sheet form and subsequently underwent solution-aging and annealing. Through electrochemical examinations and microstructure characterization, the study assessed the influence of inclusions on the corrosion resistance of the recycled Al-Zn-Mg-Cu alloy within an environment of near-neutral pH containing chlorine. The findings suggest that the presence of inclusions in recycled aluminum predominantly affects corrosion resistance by inducing microdefects in the neighboring matrix and by changing the grain structure. The shift in grain structure is particularly influential on the electrochemical properties of the recycled sheets, with an enhanced effect in the specimens treated with solid solution-aging.
{"title":"Effect of micron-sized inclusions on the corrosion behavior of recycled Al-Zn-Mg-Cu alloy sheet","authors":"Sen Du , Mingtao Wang , Shengen Zhang , Zhengfeng Lv , Zhiyuan Xu , Chen Liu , Jingtao Wang , Jun Liu , Bo Liu","doi":"10.1016/j.matchar.2024.114517","DOIUrl":"10.1016/j.matchar.2024.114517","url":null,"abstract":"<div><div>The remelted aluminum scrap exhibits elevated inclusion levels, a condition inadequately addressed by contemporary refining methodologies, particularly with respect to the extraction of diminutive inclusions. The objective of this investigation is to delineate the repercussions of micron-scale inclusions on the corrosion behavior of recycled Al-Zn-Mg-Cu alloy sheets. Aluminum melts, varying in cleanliness, were reprocessed into sheet form and subsequently underwent solution-aging and annealing. Through electrochemical examinations and microstructure characterization, the study assessed the influence of inclusions on the corrosion resistance of the recycled Al-Zn-Mg-Cu alloy within an environment of near-neutral pH containing chlorine. The findings suggest that the presence of inclusions in recycled aluminum predominantly affects corrosion resistance by inducing microdefects in the neighboring matrix and by changing the grain structure. The shift in grain structure is particularly influential on the electrochemical properties of the recycled sheets, with an enhanced effect in the specimens treated with solid solution-aging.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114517"},"PeriodicalIF":4.8,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.matchar.2024.114531
Tengfeng Feng , Zhanglai Pan , Ningxin Li , Peiqian Zhang , Shanglin Zhang , Xinkai Ma
TRIP/TWIP metastable β titanium alloys demonstrate high strain hardening rates and excellent tensile ductility. However, the precipitation of nanometer-sized ω phase through microstructural control significantly improves strength but often results in a significant decrease in ductility. This research proposes a novel strategy by precipitating isothermal ω phase (ωiso) and integrating mechanical twinning/martensitic transformation to address these challenges. The single-phase β coarse-grained (CG) specimens of metastable Ti25Nb (at.%) alloy were subjected to solution treatment in the β phase region, followed by aging at 300 °C for 60 min to obtain CG60. The ωiso-reinforced CG60 specimen exhibited a 12 % uniform elongation (1 % higher than CG specimen) and a yield strength of 857 MPa (approximately 67 % higher than CG specimens). In the CG60 specimen, deformation mechanisms were mainly attributed to the TRIP, TWIP and dislocation slip, with TWIP being predominant. As aging time increased, ω phase (localized barriers) and improved β matrix stability progressively suppressed TRIP and TWIP effects, with TWIP being completely inhibited first. Transmission electron microscopy and computational findings suggest that larger ω phase contributes more significantly to the precipitation strengthening.
{"title":"Achieving an excellent combination of strength and ductility in metastable β titanium alloys via coupling isothermal ω phase and TRIP/TWIP effects","authors":"Tengfeng Feng , Zhanglai Pan , Ningxin Li , Peiqian Zhang , Shanglin Zhang , Xinkai Ma","doi":"10.1016/j.matchar.2024.114531","DOIUrl":"10.1016/j.matchar.2024.114531","url":null,"abstract":"<div><div>TRIP/TWIP metastable β titanium alloys demonstrate high strain hardening rates and excellent tensile ductility. However, the precipitation of nanometer-sized ω phase through microstructural control significantly improves strength but often results in a significant decrease in ductility. This research proposes a novel strategy by precipitating isothermal ω phase (ω<sub>iso</sub>) and integrating mechanical twinning/martensitic transformation to address these challenges. The single-phase β coarse-grained (CG) specimens of metastable Ti<img>25Nb (at.%) alloy were subjected to solution treatment in the β phase region, followed by aging at 300 °C for 60 min to obtain CG60. The ω<sub>iso</sub>-reinforced CG60 specimen exhibited a 12 % uniform elongation (1 % higher than CG specimen) and a yield strength of 857 MPa (approximately 67 % higher than CG specimens). In the CG60 specimen, deformation mechanisms were mainly attributed to the TRIP, TWIP and dislocation slip, with TWIP being predominant. As aging time increased, ω phase (localized barriers) and improved β matrix stability progressively suppressed TRIP and TWIP effects, with TWIP being completely inhibited first. Transmission electron microscopy and computational findings suggest that larger ω phase contributes more significantly to the precipitation strengthening.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114531"},"PeriodicalIF":4.8,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-07DOI: 10.1016/j.matchar.2024.114532
Jinhan Zhang , Jingtai Yu , Xiaoran Wei , Kun Zhou , Weifei Niu , Yushun Wei , Cong Zhao , Gang Chen , Fengmin Jin , Kai Song
To provide an on-site metallographic segmentation using only optical microscopy images, sSEM-Net, a soft scanning electron microscopy network, is developed based on a self-supervised pre-training deep learning framework. During model training, only a sparse collection of SEM images is necessary for annotation assistance. By integrating CNN and Transformer, sSEM-Net efficiently utilizes global context information while mitigating data dependency and computational resource constraints. Using only readily available optical microscopy images as input, sSEM-Net achieves metallographic segmentation comparable to SEM images, catering to rapid and cost-effective industrial needs. This methodology leverages non-destructive inspection attributes, catering to rapid and cost-sensitive industrial requirements. The efficacy of the proposed sSEM-Net is demonstrated through metallographic structure analysis of TC4 titanium alloy, with potential extensions to other alloy types.
{"title":"A soft scanning electron microscopy for efficient segmentation of alloy microstructures based on a new self-supervised pre-training deep learning network","authors":"Jinhan Zhang , Jingtai Yu , Xiaoran Wei , Kun Zhou , Weifei Niu , Yushun Wei , Cong Zhao , Gang Chen , Fengmin Jin , Kai Song","doi":"10.1016/j.matchar.2024.114532","DOIUrl":"10.1016/j.matchar.2024.114532","url":null,"abstract":"<div><div>To provide an on-site metallographic segmentation using only optical microscopy images, sSEM-Net, a soft scanning electron microscopy network, is developed based on a self-supervised pre-training deep learning framework. During model training, only a sparse collection of SEM images is necessary for annotation assistance. By integrating CNN and Transformer, sSEM-Net efficiently utilizes global context information while mitigating data dependency and computational resource constraints. Using only readily available optical microscopy images as input, sSEM-Net achieves metallographic segmentation comparable to SEM images, catering to rapid and cost-effective industrial needs. This methodology leverages non-destructive inspection attributes, catering to rapid and cost-sensitive industrial requirements. The efficacy of the proposed sSEM-Net is demonstrated through metallographic structure analysis of TC4 titanium alloy, with potential extensions to other alloy types.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114532"},"PeriodicalIF":4.8,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.matchar.2024.114499
Xin Liu, Zheye Liu, Ye Zhang, Yu Xiao, Zhiyuan Feng, Kaiyu Zhang, Wanliang Zhang, Chengshuang Zhou, Lin Zhang
To synergistically enhance the strength and toughness of titanium-free maraging steel, a multi-scale characterization method was used to illustrate the effects of low-temperature solution treatment and double aging treatment on the microstructure of titanium-free maraging steel in this paper. After the low-temperature solution treatment and the double aging treatment, the tensile strength of titanium-free maraging steel increased from 1954 MPa to 2160 MPa and the elongation increased by 8.95 %. By the low-temperature solution treatment, the original austenite grain size of the titanium-free maraging steel was refined to 0.69 μm. The double aging treatment promoted the diffusion of Mo and Ni elements, increased the volume fraction of ω phase, Ni3Mo nano-precipitation phase and reversed austenite, and refined the size of ω phase and Ni3Mo by 14.2 % and 7.9 %, respectively. The nanoparticles of titanium-free maraging steel mainly include the ω phase, Ni3Mo and Laves phase. The strengthening mechanism of nanoparticles was quantitatively evaluated from the shear mechanism and Orowan dislocation loop mechanism. The mechanism shows that the ω phase is the main contributor to the overall precipitation strengthening. Therefore, low-temperature solution treatment and double aging treatment provide a potential solution for achieving high strength and high toughness in maraging steel.
{"title":"Synergistic regulation of nano-precipitates and reversed austenite in titanium-free maraging steel by low-temperature solution treatment and double aging treatment","authors":"Xin Liu, Zheye Liu, Ye Zhang, Yu Xiao, Zhiyuan Feng, Kaiyu Zhang, Wanliang Zhang, Chengshuang Zhou, Lin Zhang","doi":"10.1016/j.matchar.2024.114499","DOIUrl":"10.1016/j.matchar.2024.114499","url":null,"abstract":"<div><div>To synergistically enhance the strength and toughness of titanium-free maraging steel, a multi-scale characterization method was used to illustrate the effects of low-temperature solution treatment and double aging treatment on the microstructure of titanium-free maraging steel in this paper. After the low-temperature solution treatment and the double aging treatment, the tensile strength of titanium-free maraging steel increased from 1954 MPa to 2160 MPa and the elongation increased by 8.95 %. By the low-temperature solution treatment, the original austenite grain size of the titanium-free maraging steel was refined to 0.69 μm. The double aging treatment promoted the diffusion of Mo and Ni elements, increased the volume fraction of ω phase, Ni<sub>3</sub>Mo nano-precipitation phase and reversed austenite, and refined the size of ω phase and Ni<sub>3</sub>Mo by 14.2 % and 7.9 %, respectively. The nanoparticles of titanium-free maraging steel mainly include the ω phase, Ni<sub>3</sub>Mo and Laves phase. The strengthening mechanism of nanoparticles was quantitatively evaluated from the shear mechanism and Orowan dislocation loop mechanism. The mechanism shows that the ω phase is the main contributor to the overall precipitation strengthening. Therefore, low-temperature solution treatment and double aging treatment provide a potential solution for achieving high strength and high toughness in maraging steel.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114499"},"PeriodicalIF":4.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The material in wire arc additive manufacturing (WAAM) undergoes complex material flow and multiple thermal heating and cooling cycles, forming highly heterogeneous microstructures in terms of size, crystallographic orientations, and mechanical properties. The inhomogeneity also depends on the dislocation density and phases, which are influenced by the thermal history of the process. In this study, the Cold Metal Transfer (CMT) process was used to deposit a 60-layer build of Inconel 625 alloy. Detailed variations in the microstructural size, orientations, and phases along the building direction were studied using optical microscopy, electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Microstructural observations reveal dendrites, equiaxed crystals, cellular, and columnar structures with primary and secondary dendrites. Dynamic recrystallization (DRX) followed by abnormal grain growth was found in the build. The average grain size varies with deposited height, with a grain size of around 13 ± 1 μm near the substrate, 45 ± 1 μm in the middle region, and 18 ± 1 μm at the top. The top region exhibited a strong intensity of recrystallized Cube, Cube-ND, and Cube-RD textures, with weaker intensities of copper and brass textures. The middle and bottom regions show strong intensities of Goss, copper, F, S, and E textures, respectively. The highest dislocation density of 5.122 × 10−4 nm−2 was found in the top region, while the lowest (4.14 × 10−4 nm−2) was observed in the bottom region. The ultimate tensile strength of the build ranged from 603 ± 05 MPa to 699 ± 10 MPa, while the yield strength varied from 313 ± 07 MPa to 365 ± 08 MPa along different orientations. Vickers hardness results showed a slight variation, from 240 ± 5 to 260 ± 2 HV, from bottom to the top of the deposited build. The findings from this study provide valuable insights into the microstructural evolution mechanism and mechanical behavior of WAAM-fabricated Inconel 625, which can guide other researchers in optimizing process parameters, enhancing material properties, and understanding the effects of thermal history on additive manufacturing of high-performance alloys.
{"title":"Microstructural evolution, crystallographic texture, grain morphology, and mechanical integrity of wire arc additively manufactured Inconel 625 alloy","authors":"Gaurav Kishor , Krishna Kishore Mugada , Raju Prasad Mahto , Aravindan Sivanandam , Ravi Kumar Digavalli , Murugaiyan Amirthalingam","doi":"10.1016/j.matchar.2024.114525","DOIUrl":"10.1016/j.matchar.2024.114525","url":null,"abstract":"<div><div>The material in wire arc additive manufacturing (WAAM) undergoes complex material flow and multiple thermal heating and cooling cycles, forming highly heterogeneous microstructures in terms of size, crystallographic orientations, and mechanical properties. The inhomogeneity also depends on the dislocation density and phases, which are influenced by the thermal history of the process. In this study, the Cold Metal Transfer (CMT) process was used to deposit a 60-layer build of Inconel 625 alloy. Detailed variations in the microstructural size, orientations, and phases along the building direction were studied using optical microscopy, electron backscatter diffraction (EBSD), and X-ray diffraction (XRD). Microstructural observations reveal dendrites, equiaxed crystals, cellular, and columnar structures with primary and secondary dendrites. Dynamic recrystallization (DRX) followed by abnormal grain growth was found in the build. The average grain size varies with deposited height, with a grain size of around 13 ± 1 μm near the substrate, 45 ± 1 μm in the middle region, and 18 ± 1 μm at the top. The top region exhibited a strong intensity of recrystallized Cube, Cube-ND, and Cube-RD textures, with weaker intensities of copper and brass textures. The middle and bottom regions show strong intensities of Goss, copper, F, S, and E textures, respectively. The highest dislocation density of 5.122 × 10<sup>−4</sup> nm<sup>−2</sup> was found in the top region, while the lowest (4.14 × 10<sup>−4</sup> nm<sup>−2</sup>) was observed in the bottom region. The ultimate tensile strength of the build ranged from 603 ± 05 MPa to 699 ± 10 MPa, while the yield strength varied from 313 ± 07 MPa to 365 ± 08 MPa along different orientations. Vickers hardness results showed a slight variation, from 240 ± 5 to 260 ± 2 HV, from bottom to the top of the deposited build. The findings from this study provide valuable insights into the microstructural evolution mechanism and mechanical behavior of WAAM-fabricated Inconel 625, which can guide other researchers in optimizing process parameters, enhancing material properties, and understanding the effects of thermal history on additive manufacturing of high-performance alloys.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114525"},"PeriodicalIF":4.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.matchar.2024.114527
Jie Wang, Fugang Chen, Xiaoli Wang, Yong Zhao, Juan Fu
The grain boundary diffusion process (GBDP) has become one of the main methods to enhance the coercivity of Nd-Ce-Fe-B magnets. In this study, we examined how the magnetic properties of sintered Nd-Ce-Fe-B magnets are influenced by the combined impacts of diffusion depth, Tb-rich shell thickness, and surface grain coarsening after conducting grain boundary diffusion. There exists a trade-off between achieving a desired diffusion depth and avoiding excessive surface grain coarsening. To examine this trade-off, samples with varying diffusion depths were prepared through controlled diffusion time. Results revealed that compared to the original annealed magnets, the coercivity increments of the magnets diffused for 1 h and 3 h were 148 kA/m and 290 kA/m, respectively, while the coercivity of the magnet diffused for 9 h remained nearly the same as that diffused for 3 h. Microstructural analysis indicated that surface grain coarsening intensified with increasing diffusion time, leading to a reduction in the surface diffusion channels, thereby diminishing diffusion efficiency. In addition, strong mutual diffusion was observed between the magnet and the diffusion source. Furthermore, micromagnetic simulation studies revealed that severe surface grain coarsening limits the enhancement of coercivity even with increased depth of diffusion and thickness of the Tb-rich shell layer. This study offers valuable insights into the correlation between diffusion depth, Tb-rich shell thickness, surface grain coarsening, and the ultimate magnetic properties in sintered Nd-Ce-Fe-B magnets after GBDP, providing guidance for enhancing the efficiency of GBDP.
{"title":"A trade-off between the diffusion depth, the thickness of the Tb-rich shell and the surface grain coarsening during the grain boundary diffusion of sintered Nd-Ce-Fe-B magnets","authors":"Jie Wang, Fugang Chen, Xiaoli Wang, Yong Zhao, Juan Fu","doi":"10.1016/j.matchar.2024.114527","DOIUrl":"10.1016/j.matchar.2024.114527","url":null,"abstract":"<div><div>The grain boundary diffusion process (GBDP) has become one of the main methods to enhance the coercivity of Nd-Ce-Fe-B magnets. In this study, we examined how the magnetic properties of sintered Nd-Ce-Fe-B magnets are influenced by the combined impacts of diffusion depth, Tb-rich shell thickness, and surface grain coarsening after conducting grain boundary diffusion. There exists a trade-off between achieving a desired diffusion depth and avoiding excessive surface grain coarsening. To examine this trade-off, samples with varying diffusion depths were prepared through controlled diffusion time. Results revealed that compared to the original annealed magnets, the coercivity increments of the magnets diffused for 1 h and 3 h were 148 kA/m and 290 kA/m, respectively, while the coercivity of the magnet diffused for 9 h remained nearly the same as that diffused for 3 h. Microstructural analysis indicated that surface grain coarsening intensified with increasing diffusion time, leading to a reduction in the surface diffusion channels, thereby diminishing diffusion efficiency. In addition, strong mutual diffusion was observed between the magnet and the diffusion source. Furthermore, micromagnetic simulation studies revealed that severe surface grain coarsening limits the enhancement of coercivity even with increased depth of diffusion and thickness of the Tb-rich shell layer. This study offers valuable insights into the correlation between diffusion depth, Tb-rich shell thickness, surface grain coarsening, and the ultimate magnetic properties in sintered Nd-Ce-Fe-B magnets after GBDP, providing guidance for enhancing the efficiency of GBDP.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114527"},"PeriodicalIF":4.8,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.matchar.2024.114533
Xiaoxuan Zhang , Xinhao Liu , Rengeng Li , He Wu , Yi Ma , Kesong Miao , Hao Wu , Xuewen Li , Guohua Fan
Defects are inevitable in selective laser melting process, significantly impacting the mechanical properties of materials and reducing their service life. In this study, the effects of various defects and their distribution on the high-temperature mechanical performance of the selective laser melted K418 superalloys were investigated via an in-situ 3D X-ray analysis and finite element method. The results showed that the selective laser melting process can significantly enhance the strength of the K418 sample, while degrading the fracture elongation. The sphericity and location of defects are the two key parameters influencing the mechanical performance. The defects with low sphericity at the sub-surface resulted in elevated local stress and strain, accounting for the significant degradation in fracture elongation. Locally increased stress and accumulated strain around lack of fusion defects at the sub-surface contribute to the initiation and propagation of crack. This study provides inspiration for understanding the correlation between the defects and mechanical properties.
缺陷在选择性激光熔化过程中不可避免,会严重影响材料的机械性能并降低其使用寿命。本研究通过原位三维 X 射线分析和有限元法研究了各种缺陷及其分布对选择性激光熔化 K418 超合金高温力学性能的影响。结果表明,选择性激光熔化工艺可显著提高 K418 样品的强度,同时降低断裂伸长率。缺陷的球度和位置是影响力学性能的两个关键参数。次表层球度较低的缺陷导致局部应力和应变升高,是断裂伸长率显著下降的原因。次表层缺乏融合缺陷周围的局部应力增加和应变累积导致了裂纹的产生和扩展。这项研究为理解缺陷与机械性能之间的相关性提供了启发。
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Pub Date : 2024-11-05DOI: 10.1016/j.matchar.2024.114524
Arnold Pradhan , Fei Xu , Daniele Salvato , Indrajit Charit , Colin Judge , Luca Capriotti , Tiankai Yao
Fuel cladding chemical interaction (FCCI) plays a key role in limiting the performance of metallic fuels in nuclear applications. A comprehensive analysis of chemical elements present in FCCI region is the basis for understanding the phenomena and developing potential mitigating strategies. The detection of low atomic number elements (Z < 11) and lanthanide fission products is challenging for energy dispersive x-ray spectroscopy (EDS). This work used scanning transmission electron microscopy (STEM) based electron energy loss spectroscopy (EELS) to study the distribution of carbon and lanthanides in the FCCI region of a solid U-10Zr (wt%) fuel irradiated to 13.2 at. % burnup at the Fast Flux Testing Facility (FFTF). Processing the STEM-EELS data involved three major steps: 1) enhancing the signal-to-noise ratio by denoising the STEM-EELS spectra using principal component analysis (PCA) methods; 2) identification and mapping of chemical elements with core energy loss edges; 3) microstructural phase segmentation using the K-means clustering method. STEM-EELS analysis indicated the formation of zirconium carbide, a rind-like microstructural phase, in the FCCI region between fuel and cladding. The rind appeared to remain intact at this location for the studied burnup. The study also revealed a shift in the plasmon peak between zirconium-rich region and zirconium carbide. The STEM-EELS mappings demonstrated a different distribution of Ce from other lanthanide elements, such as La, Pr, and Nd, suggesting that the effect of lanthanides in the FCCI region should be separately investigated. The use of K-means clustering method on the STEM-EELS spectra of the FCCI region revealed different phases, especially Fe-Ce and Zr-C, that concurred with the findings from STEM-EELS elemental mappings.
{"title":"Characterization of Fuel Cladding Chemical Interaction on a High Burnup U-10Zr Metallic Fuel via Electron Energy Loss Spectroscopy Enhanced by Machine Learning","authors":"Arnold Pradhan , Fei Xu , Daniele Salvato , Indrajit Charit , Colin Judge , Luca Capriotti , Tiankai Yao","doi":"10.1016/j.matchar.2024.114524","DOIUrl":"10.1016/j.matchar.2024.114524","url":null,"abstract":"<div><div>Fuel cladding chemical interaction (FCCI) plays a key role in limiting the performance of metallic fuels in nuclear applications. A comprehensive analysis of chemical elements present in FCCI region is the basis for understanding the phenomena and developing potential mitigating strategies. The detection of low atomic number elements (Z < 11) and lanthanide fission products is challenging for energy dispersive x-ray spectroscopy (EDS). This work used scanning transmission electron microscopy (STEM) based electron energy loss spectroscopy (EELS) to study the distribution of carbon and lanthanides in the FCCI region of a solid U-10Zr (wt%) fuel irradiated to 13.2 at. % burnup at the Fast Flux Testing Facility (FFTF). Processing the STEM-EELS data involved three major steps: 1) enhancing the signal-to-noise ratio by denoising the STEM-EELS spectra using principal component analysis (PCA) methods; 2) identification and mapping of chemical elements with core energy loss edges; 3) microstructural phase segmentation using the K-means clustering method. STEM-EELS analysis indicated the formation of zirconium carbide, a rind-like microstructural phase, in the FCCI region between fuel and cladding. The rind appeared to remain intact at this location for the studied burnup. The study also revealed a shift in the plasmon peak between zirconium-rich region and zirconium carbide. The STEM-EELS mappings demonstrated a different distribution of Ce from other lanthanide elements, such as La, Pr, and Nd, suggesting that the effect of lanthanides in the FCCI region should be separately investigated. The use of K-means clustering method on the STEM-EELS spectra of the FCCI region revealed different phases, especially Fe-Ce and Zr-C, that concurred with the findings from STEM-EELS elemental mappings.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"218 ","pages":"Article 114524"},"PeriodicalIF":4.8,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}