This paper describes a novel in-situ adjustment method of static magnetic field (SMF) for laser additive manufacturing, which realizes the change of grain morphology and weave structure without changing the composition and performing post-processing. The TC11 alloy was prepared by laser direct energy deposition (LDED) under static SMF. The results show that a transverse static SMF of 0.5 T effectively suppresses the tendency of columnar crystals to grow continuously along the build direction and the dominant weaving direction of 〈0001〉 texture, and reduces the anisotropy of the TC11 alloy.
{"title":"Grain structure control of TC11 alloy in laser direct energy deposition by a static magnetic field","authors":"Chunlun Chen, Haobo Sun, Zhenlin Zhang, Yongsheng Zhao, Yan Liu, Hui Chen","doi":"10.1016/j.mtla.2024.102267","DOIUrl":"10.1016/j.mtla.2024.102267","url":null,"abstract":"<div><div>This paper describes a novel in-situ adjustment method of static magnetic field (SMF) for laser additive manufacturing, which realizes the change of grain morphology and weave structure without changing the composition and performing post-processing. The TC11 alloy was prepared by laser direct energy deposition (LDED) under static SMF. The results show that a transverse static SMF of 0.5 T effectively suppresses the tendency of columnar crystals to grow continuously along the build direction and the dominant weaving direction of 〈0001〉 texture, and reduces the anisotropy of the TC11 alloy.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102267"},"PeriodicalIF":3.0,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537980","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}
Pub Date : 2024-10-19DOI: 10.1016/j.mtla.2024.102270
A. Houba , M. El Ayoubi , A. Samiri , A. Atila , A. Hasnaoui
In this study, molecular dynamics (MD) simulations were utilized to explore the Short and Medium-Range Order (MRO) in the rapidly solidified metallic liquid tantalum (Ta). Radial distribution function (RDF) and Voronoi tessellation analysis (VTA) techniques were employed to thoroughly explore the effect of pressure on the connectivity and structural properties at the Short-Range Order (SRO) and MRO levels. Our findings indicate that, at a quenching rate of 1013 K s-1, glassy states are achieved at or below 20 GPa, while crystalline phases emerge at 25 GPa. VTA analysis indicates a significant alteration in the local structure of glassy Ta with increasing pressure. Specifically, the fraction of icosahedral-like clusters decreases while the fraction of crystal-like clusters rises notably.
Furthermore, we highlight that icosahedral-like clusters strongly tend to form 3-atom connection mode, while crystal-like clusters prefer 2-atom and 4-atom connection modes. Notably, icosahedral-like clusters are identified as the primary contributors to the emergence of the left sub-peak in the second peak of the RDF. In contrast, all cluster types contribute to the appearance of the right sub-peak.
{"title":"Short and medium range order in the rapidly solidified metallic liquid Ta: Atomic packing, connection modes, and pressure effect","authors":"A. Houba , M. El Ayoubi , A. Samiri , A. Atila , A. Hasnaoui","doi":"10.1016/j.mtla.2024.102270","DOIUrl":"10.1016/j.mtla.2024.102270","url":null,"abstract":"<div><div>In this study, molecular dynamics (<em>MD</em>) simulations were utilized to explore the Short and Medium-Range Order (<em>MRO</em>) in the rapidly solidified metallic liquid tantalum (<em>Ta</em>). Radial distribution function (<em>RDF</em>) and Voronoi tessellation analysis (<em>VTA</em>) techniques were employed to thoroughly explore the effect of pressure on the connectivity and structural properties at the Short-Range Order (<em>SRO</em>) and <em>MRO</em> levels. Our findings indicate that, at a quenching rate of 10<sup>13</sup> K s<sup>-1</sup>, glassy states are achieved at or below 20 GPa, while crystalline phases emerge at 25 GPa. <em>VTA</em> analysis indicates a significant alteration in the local structure of glassy <em>Ta</em> with increasing pressure. Specifically, the fraction of icosahedral-like clusters decreases while the fraction of crystal-like clusters rises notably.</div><div>Furthermore, we highlight that icosahedral-like clusters strongly tend to form 3-atom connection mode, while crystal-like clusters prefer 2-atom and 4-atom connection modes. Notably, icosahedral-like clusters are identified as the primary contributors to the emergence of the left sub-peak in the second peak of the <em>RDF</em>. In contrast, all cluster types contribute to the appearance of the right sub-peak.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102270"},"PeriodicalIF":3.0,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537985","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}
Pub Date : 2024-10-16DOI: 10.1016/j.mtla.2024.102262
Lucas Varoto , Pierre Lhuissier , Marta Majkut , Jean-Jacques Blandin , Sophie Roure , Anthony Papillon , Mélissa Chosson , Guilhem Martin
Cu-Cr alloys are used as electrical contacts for medium voltage applications because of their desirable trade-off between electrical, thermal, and mechanical properties. However, few studies have investigated the microstructural evolutions caused by an electrical arc during an electrical breakdown. Herein, electron beam melting of a Cu-25Cr (wt.%) composite fabricated by solid-state sintering is used to mimic the thermal conditions of an electrical arc. The microstructure before and after melting was characterized using synchrotron x-ray computed microtomography and directly correlated with post-mortem electron microscopy observations. The melt pool consists of different zones: a fusion zone characterized by the complete melt of both Cu and Cr phases, and a partially melted zone where only the Cu phase is melted. Pores in the matrix or at the Cu/Cr interfaces are healed upon melting. Tracking large Cr-particles reveals significant spatial evolutions attributed to convective flows.
Cu-Cr 合金因其电气、热和机械性能之间的理想平衡而被用作中压应用中的电触点。然而，很少有研究对电击过程中电弧引起的微结构演变进行调查。本文采用电子束熔化固态烧结制造的铜-25Cr（重量百分比）复合材料的方法来模拟电弧的热条件。利用同步辐射 X 射线计算机显微层析技术对熔化前后的微观结构进行了表征，并与死后电子显微镜观察结果直接相关。熔池由不同的区域组成：熔融区的特点是铜相和铬相完全熔化，而部分熔化区则只熔化了铜相。基体中或铜/铬界面上的孔隙在熔化后愈合。跟踪大的铬颗粒可以发现对流造成的显著空间变化。
{"title":"Microstructure evolutions induced by electron beam melting of a sintered Cu-25Cr composite","authors":"Lucas Varoto , Pierre Lhuissier , Marta Majkut , Jean-Jacques Blandin , Sophie Roure , Anthony Papillon , Mélissa Chosson , Guilhem Martin","doi":"10.1016/j.mtla.2024.102262","DOIUrl":"10.1016/j.mtla.2024.102262","url":null,"abstract":"<div><div>Cu-Cr alloys are used as electrical contacts for medium voltage applications because of their desirable trade-off between electrical, thermal, and mechanical properties. However, few studies have investigated the microstructural evolutions caused by an electrical arc during an electrical breakdown. Herein, electron beam melting of a Cu-25Cr (wt.%) composite fabricated by solid-state sintering is used to mimic the thermal conditions of an electrical arc. The microstructure before and after melting was characterized using synchrotron x-ray computed microtomography and directly correlated with post-mortem electron microscopy observations. The melt pool consists of different zones: a fusion zone characterized by the complete melt of both Cu and Cr phases, and a partially melted zone where only the Cu phase is melted. Pores in the matrix or at the Cu/Cr interfaces are healed upon melting. Tracking large Cr-particles reveals significant spatial evolutions attributed to convective flows.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102262"},"PeriodicalIF":3.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573446","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}
Pub Date : 2024-10-16DOI: 10.1016/j.mtla.2024.102248
Hamza Elbaza , Hanaa Mabroum , El Mehdi Toufik , Badre Eddine Halimi , Yousra Hamdan , Rachid El Fatimy , Hicham Ben youcef , Christèle Combes , Allal Barroug , Hassan Noukrati
The present work focuses on the development of composite cements based on dicalcium phosphate dihydrate (DCPD), calcium carbonate CaCO3, sodium alginate (AG), and sodium fusidate (FS). The effect of AG, setting accelerator (0.5 M of Na2HPO4), and antibacterial agent (FS) on the features (setting ability, injectability, cohesion, and compressive strength) of DCPD-CaCO3-based cement was investigated. The reference and composite cements are composed of a nanocrystalline carbonated apatite, similar to bone mineral, and an excess of unreacted vaterite (CaCO3). The incorporation of AG increased the composite cement's total porosity compared to the reference cement (CR). The evaluation of the injectability and cohesion properties showed that adding 10 wt % of AG resulted in a total extrusion of the paste with an improvement in the cohesion of the cement paste. The compressive strength of the cements raised from 3.2 for CR up to 7 MPa with the addition of 10 % of AG and Na2HPO4 . The setting time is significantly reduced by introducing Na2HPO4, resulting in appropriate values (≤ 30 min) for clinical use. Moreover, incorporating 3 wt % of FS in the composite cements had no significant effect on their features. The release study of FS-loaded composites showed sustained and controlled release profiles, with daily released amounts at the therapeutic level. The antibacterial activity of the designed FS-loaded composites demonstrated the effectiveness of the specimens in inhibiting the growth of S. Aureus. Furthermore, the in vitro biological tests did not show any toxicity of the tested cements towards hPBMCs, thereby confirming their biocompatibility.
{"title":"Delivery of sodium fusidate from alginate-reinforced, carbonated apatite cement: Physicochemical properties, release behavior, antibacterial and cytotoxicity properties","authors":"Hamza Elbaza , Hanaa Mabroum , El Mehdi Toufik , Badre Eddine Halimi , Yousra Hamdan , Rachid El Fatimy , Hicham Ben youcef , Christèle Combes , Allal Barroug , Hassan Noukrati","doi":"10.1016/j.mtla.2024.102248","DOIUrl":"10.1016/j.mtla.2024.102248","url":null,"abstract":"<div><div>The present work focuses on the development of composite cements based on dicalcium phosphate dihydrate (DCPD), calcium carbonate CaCO<sub>3</sub>, sodium alginate (AG), and sodium fusidate (FS). The effect of AG, setting accelerator (0.5 M of Na<sub>2</sub>HPO<sub>4</sub>), and antibacterial agent (FS) on the features (setting ability, injectability, cohesion, and compressive strength) of DCPD-CaCO<sub>3</sub>-based cement was investigated. The reference and composite cements are composed of a nanocrystalline carbonated apatite, similar to bone mineral, and an excess of unreacted vaterite (CaCO<sub>3</sub>). The incorporation of AG increased the composite cement's total porosity compared to the reference cement (CR). The evaluation of the injectability and cohesion properties showed that adding 10 wt % of AG resulted in a total extrusion of the paste with an improvement in the cohesion of the cement paste. The compressive strength of the cements raised from 3.2 for CR up to 7 MPa with the addition of 10 % of AG and Na<sub>2</sub>HPO<sub>4</sub> . The setting time is significantly reduced by introducing Na<sub>2</sub>HPO<sub>4</sub>, resulting in appropriate values (≤ 30 min) for clinical use. Moreover, incorporating 3 wt % of FS in the composite cements had no significant effect on their features. The release study of FS-loaded composites showed sustained and controlled release profiles, with daily released amounts at the therapeutic level. The antibacterial activity of the designed FS-loaded composites demonstrated the effectiveness of the specimens in inhibiting the growth of <em>S. Aureus</em>. Furthermore, the in vitro biological tests did not show any toxicity of the tested cements towards hPBMCs, thereby confirming their biocompatibility.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102248"},"PeriodicalIF":3.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537978","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}
Quenching and partitioning (Q&P) processing is a widely accepted heat treatment methodology for creating high strength steels consisting of ferrite, martensite, and austenite, while maintaining relatively low manufacturing costs. Though the research on effects of prior microstructure is limited, an understanding of the heat treatment response of different starting microstructures is critical to processing and creating steels with complex microstructures that contain retained austenite and may afford opportunities to further optimize properties. This study investigates the influence of starting microstructure (ferrite/pearlite versus martensite) and prior levels of cold work (38 verses 58 %) on the microstructural development and mechanical properties of a 0.2 C-2.0 Mn-1.5 Si (wt.%) steel exposed to Q&P processing. Samples with a starting martensitic microstructure resulted in higher retained austenite fractions and a more homogeneous microstructure after Q&P processing compared to a starting microstructure of ferrite-pearlite. Starting martensitic microstructures also displayed higher work hardening rates and higher uniform elongations. Larger cold reductions saw accelerated dissolution kinetics and austenite formation during intercritical annealing, resulting in more similar final microstructures from the ferrite-pearlite and martensitic starting microstructures. The results presented here indicate that varying prior processing can be a route to manipulate and control austenite stability in a Q&P processed steel.
{"title":"Tuning austenite stability through prior microstructure control in a low-alloy Q&P steel","authors":"Melissa Thrun , Virginia Euser , Amy Clarke , Kester Clarke","doi":"10.1016/j.mtla.2024.102261","DOIUrl":"10.1016/j.mtla.2024.102261","url":null,"abstract":"<div><div>Quenching and partitioning (Q&P) processing is a widely accepted heat treatment methodology for creating high strength steels consisting of ferrite, martensite, and austenite, while maintaining relatively low manufacturing costs. Though the research on effects of prior microstructure is limited, an understanding of the heat treatment response of different starting microstructures is critical to processing and creating steels with complex microstructures that contain retained austenite and may afford opportunities to further optimize properties. This study investigates the influence of starting microstructure (ferrite/pearlite versus martensite) and prior levels of cold work (38 verses 58 %) on the microstructural development and mechanical properties of a 0.2 C-2.0 Mn-1.5 Si (wt.%) steel exposed to Q&P processing. Samples with a starting martensitic microstructure resulted in higher retained austenite fractions and a more homogeneous microstructure after Q&P processing compared to a starting microstructure of ferrite-pearlite. Starting martensitic microstructures also displayed higher work hardening rates and higher uniform elongations. Larger cold reductions saw accelerated dissolution kinetics and austenite formation during intercritical annealing, resulting in more similar final microstructures from the ferrite-pearlite and martensitic starting microstructures. The results presented here indicate that varying prior processing can be a route to manipulate and control austenite stability in a Q&P processed steel.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102261"},"PeriodicalIF":3.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446977","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}
Pub Date : 2024-10-15DOI: 10.1016/j.mtla.2024.102260
I. Daki , N. Saloumi , C. Assamadi , A. Ouafik , S. Mansouri , M. Yousfi , J-F. Gérard , J. Duchet-Rumeau , M. Oumam , O. Cherkaoui , H. Hannache , M. El Bouchti
Nowadays, phosphate glass fibers (PGF) are considered quite competitive respective to conventional glass fibers. This work focus on the development of PGF fibers intended for structural engineering applications such as composite reinforcement for building and automotive fields. For this purpose, two series of phosphate glasses based on 52P2O5–24CaO-13MgO-(11-(X+ Y + Z)) K2O-XAL2O3-YF2O3-ZTiO2; (X=1; 3; 5, Y=0; 5, Z=0; 1 mol%) were processed and transformed into phosphate glass fibers by melt spinning. The resulting fibers were characterized. XRD analysis confirmed the non-crystalline nature of phosphate glasses. In addition, the substitution of K2O by Al2O3 and by the combination of Al2O3, Fe2O3 and TiO2 in the composition of phosphate glass could lead to a significant increase in fiber density from 2,16 g/cm3 to 2,80 g/cm3. The stability of the produced phosphate glass fibers was examined using two methods: weight loss at 37 °C and dissolution kinetics under different pH levels (4, 7, and 12). The results showed that the chemical resistance of the PGF fibers was improved with up to 99 % increase respective to the original formulation. In addition, the mechanical properties of the spinnable phosphate glass manufactured by replacing K2O oxide by Al2O3 oxide were improved, such a substitution led to a maximum tensile strength and modulus of 2668 MPa and 140 GPa, respectively. Therefore, the tensile proprieties were improved by 75 % compared to the original formulation. This comparative study between phosphate glass fibers (PGF) and traditional fibers highlight similar tensile strength but combined to notable enhancements in chemical stability through cation addition, expanding their potential use in composite and biomedical materials. Finally, a correlation analysis of mechanical performances was carried out. It was observed that the results obtained using the statistical methods were consistent with the experimental data.
{"title":"Synthesis and characterization of new continuous phosphate glass fibers intended for structural engineering applications: Structure/property relationships","authors":"I. Daki , N. Saloumi , C. Assamadi , A. Ouafik , S. Mansouri , M. Yousfi , J-F. Gérard , J. Duchet-Rumeau , M. Oumam , O. Cherkaoui , H. Hannache , M. El Bouchti","doi":"10.1016/j.mtla.2024.102260","DOIUrl":"10.1016/j.mtla.2024.102260","url":null,"abstract":"<div><div>Nowadays, phosphate glass fibers (PGF) are considered quite competitive respective to conventional glass fibers. This work focus on the development of PGF fibers intended for structural engineering applications such as composite reinforcement for building and automotive fields. For this purpose, two series of phosphate glasses based on 52P<sub>2</sub>O<sub>5</sub>–24CaO-13MgO-(11-(<em>X</em>+ <em>Y</em> + <em>Z</em>)) K2O-XAL<sub>2</sub>O<sub>3</sub>-YF<sub>2</sub>O<sub>3</sub>-ZTiO<sub>2</sub>; (<em>X</em>=1; 3; 5, <em>Y</em>=0; 5, <em>Z</em>=0; 1 mol%) were processed and transformed into phosphate glass fibers by melt spinning. The resulting fibers were characterized. XRD analysis confirmed the non-crystalline nature of phosphate glasses. In addition, the substitution of K<sub>2</sub>O by Al<sub>2</sub>O<sub>3</sub> and by the combination of Al<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> in the composition of phosphate glass could lead to a significant increase in fiber density from 2,16 g/cm<sup>3</sup> to 2,80 g/cm<sup>3</sup>. The stability of the produced phosphate glass fibers was examined using two methods: weight loss at 37 °C and dissolution kinetics under different pH levels (4, 7, and 12). The results showed that the chemical resistance of the PGF fibers was improved with up to 99 % increase respective to the original formulation. In addition, the mechanical properties of the spinnable phosphate glass manufactured by replacing K<sub>2</sub>O oxide by Al<sub>2</sub>O<sub>3</sub> oxide were improved, such a substitution led to a maximum tensile strength and modulus of 2668 MPa and 140 GPa, respectively. Therefore, the tensile proprieties were improved by 75 % compared to the original formulation. This comparative study between phosphate glass fibers (PGF) and traditional fibers highlight similar tensile strength but combined to notable enhancements in chemical stability through cation addition, expanding their potential use in composite and biomedical materials. Finally, a correlation analysis of mechanical performances was carried out. It was observed that the results obtained using the statistical methods were consistent with the experimental data.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102260"},"PeriodicalIF":3.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537984","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}
Pub Date : 2024-10-15DOI: 10.1016/j.mtla.2024.102264
Wenguang Liao , Veronika Mazánová , Milan Heczko , Wenkao Hou , John Procario , Michael J. Mills , Xun Liu
Niobium (Nb) is a widely recognized micro-alloying element due to its low cost and substantial impact on steel properties. While the effect of Nb in processed steels has been well investigated, studies on its elemental distribution and precipitation behavior in weld metal remain scarce. This study focuses on the weld metal of specially designed Nb-rich X70 pipeline steel by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) characterization, complemented with thermodynamic and kinetics modeling analysis. In the majority of the weld, Nb was essentially uniformly distributed. This suggests that Nb primarily exists in the solid solution form in the weld metal, which is also supported by precipitation kinetics modeling results. This is primarily due to the short thermal history associated with the welding process, which leads to insufficient time for the uniform precipitation of Nb. Two instances of Nb precipitates were observed at the weld centerline and reinforcement region. The low partition coefficient of Nb results in an elevated local concentration along the weld centerline. However, precipitation kinetics calculations suggest that this enhancement alone is not adequate to induce precipitate formation. The occurrence of MnS and the prior formation of Ti precipitates may provide heterogeneous nucleation sites for Nb, facilitating the nucleation of Nb precipitates in the weld centerline and reinforcement region.
铌（Nb）是一种被广泛认可的微合金元素，因其成本低且对钢的性能有重大影响。虽然铌在加工钢中的影响已经得到了很好的研究，但有关其元素分布和在焊接金属中的析出行为的研究仍然很少。本研究通过扫描透射电子显微镜（STEM）和能量色散 X 射线光谱（EDS）表征，并辅以热力学和动力学建模分析，重点研究了专门设计的富铌 X70 管线钢的焊缝金属。在大部分焊缝中，铌基本上均匀分布。这表明铌主要以固溶体形式存在于焊缝金属中，沉淀动力学建模结果也证明了这一点。这主要是由于焊接过程的热历史较短，导致铌没有足够的时间均匀析出。在焊接中心线和加固区域观察到两次铌析出。由于铌的分配系数较低，导致沿焊接中心线的局部浓度升高。然而，沉淀动力学计算表明，仅靠这种提高不足以诱导沉淀形成。MnS 的出现和之前 Ti 沉淀的形成可能为 Nb 提供了异质成核位点，促进了 Nb 沉淀在焊接中心线和加固区域的成核。
{"title":"Underlying mechanisms for the effect of Nb micro-alloying on the elemental distribution and precipitation behavior in the X70 weld metal","authors":"Wenguang Liao , Veronika Mazánová , Milan Heczko , Wenkao Hou , John Procario , Michael J. Mills , Xun Liu","doi":"10.1016/j.mtla.2024.102264","DOIUrl":"10.1016/j.mtla.2024.102264","url":null,"abstract":"<div><div>Niobium (Nb) is a widely recognized micro-alloying element due to its low cost and substantial impact on steel properties. While the effect of Nb in processed steels has been well investigated, studies on its elemental distribution and precipitation behavior in weld metal remain scarce. This study focuses on the weld metal of specially designed Nb-rich X70 pipeline steel by scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) characterization, complemented with thermodynamic and kinetics modeling analysis. In the majority of the weld, Nb was essentially uniformly distributed. This suggests that Nb primarily exists in the solid solution form in the weld metal, which is also supported by precipitation kinetics modeling results. This is primarily due to the short thermal history associated with the welding process, which leads to insufficient time for the uniform precipitation of Nb. Two instances of Nb precipitates were observed at the weld centerline and reinforcement region. The low partition coefficient of Nb results in an elevated local concentration along the weld centerline. However, precipitation kinetics calculations suggest that this enhancement alone is not adequate to induce precipitate formation. The occurrence of MnS and the prior formation of Ti precipitates may provide heterogeneous nucleation sites for Nb, facilitating the nucleation of Nb precipitates in the weld centerline and reinforcement region.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102264"},"PeriodicalIF":3.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537986","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}
Pub Date : 2024-10-15DOI: 10.1016/j.mtla.2024.102263
S. Gholizadeh , S Chung Kim Yuen , S.L. George
Mechanical loading causes material deformation, resulting in changes in mechanical properties due to microstructural alterations such as the multiplication of dislocations and evolution of grain morphology. Blast loading, a condition where materials deform at high strain rates, results in significant plastic deformation. This rapid deformation induces intense mechanical stresses, causing complex microstructural changes that influence the mechanical behavior and performance of the materials. Consequently, designing structures to withstand blast loading requires understanding the relationship between microstructure and property evolution. As the primary objective of this study, post-localized blast experiments have been conducted to elucidate the variability in microstructural response of Austenitic stainless steel (ASS) 316 L, characterized by its face-centered cubic crystal structure. Localized blast loads were applied to square test plates, 2 mm thick, with a circular exposed area of 106 mm in diameter. Quantitative mechanical property data from key zones within the deformed dome were determined through using a novel micro-tensile testing approach and nanoindentation tests. Electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM) technique was employed to characterize the microstructural changes in the selected samples. The results revealed that blast loading induced complex mechanical and microstructural changes in ASS 316 L, including enhanced material strength, reduced ductility, and significant alterations in grain orientation and misorientation distributions. The materials underwent significant strain hardening due to the increased stress and deformation, resulting in a more resistant to plastic deformation and the greatest internal strain accumulations. Texture analysis underscored the influence of deformation geometry, with Goss and Copper emerging as predominant texture components.
机械加载会导致材料变形，从而引起微观结构的改变，如位错的增加和晶粒形态的演变，从而导致机械性能的变化。爆破加载是一种材料以高应变率变形的条件，会导致显著的塑性变形。这种快速变形会引起强烈的机械应力，导致复杂的微观结构变化，从而影响材料的机械行为和性能。因此，要设计出能承受爆炸荷载的结构，就必须了解微观结构与性能演变之间的关系。本研究的主要目标是进行局部爆炸后实验，以阐明奥氏体不锈钢 (ASS) 316 L 微结构响应的变化，其特点是面心立方晶体结构。对厚度为 2 毫米、圆形暴露区直径为 106 毫米的方形测试板施加了局部爆炸载荷。通过使用新型微拉伸测试方法和纳米压痕测试，确定了变形穹顶内关键区域的定量机械性能数据。扫描电子显微镜（SEM）技术中的电子反向散射衍射（EBSD）被用来表征所选样品的微观结构变化。结果表明，爆炸加载导致 ASS 316 L 发生了复杂的机械和微观结构变化，包括材料强度提高、延展性降低以及晶粒取向和错取向分布的显著改变。由于应力和变形的增加，材料发生了明显的应变硬化，从而产生了更强的抗塑性变形能力和最大的内部应变累积。纹理分析强调了变形几何形状的影响，戈斯和铜成为主要的纹理成分。
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Pub Date : 2024-10-12DOI: 10.1016/j.mtla.2024.102259
Apoorv Sobti , Kallol Mondal , Ranjit Kumar Ray , S. Sankaran
An attempt has been made to compare the effects of small reduction cold and cryo-rolling on the microstructural evolution and stability of retained austenite in a 3rd generation advanced high-strength bainitic steel. The steel was heat treated and isothermally held at 300 °C for 2 h above Ms temperature to obtain bainitic microstructure. The heat-treated steel was subsequently subjected to cold-rolling and cryo-rolling (10 % reduction in thickness). The substructure of bainite consists of packets, blocks, and sub-blocks. Both the crystallite size and micro-strain of bainitic ferrite shows a decreasing trend after rolling compared to the undeformed condition. However, cryo-rolling induces higher micro-strain in retained austenite, which enhances its mechanical stability requiring higher stress to trigger the transformation induced plasticity (TRIP) effect, thus contributing to increased overall strength. Crystallographic variant analysis showed an increase in the boundary density and frequency of specific V1-V3(V5) (high angle block boundaries) and V1-V4 (sub-block boundaries) variant pairs after cryo-rolling following the K-S orientation relationship. While the heat-treated, undeformed state exhibited all the variants without preference for any particular variant pair. The results suggest that the mechanical properties of the steel after minor cryo-rolling are significantly influenced by crystallographic variant pairing and microstrain. Additionally, minor cryo-rolling proved to be superior to cold rolling in bainitic steel as it increased the threshold strain required for the TRIP effect during rolling.
我们尝试比较小还原冷轧和低温轧制对第三代高级高强度贝氏体钢的微观结构演变和残余奥氏体稳定性的影响。该钢经过热处理，并在高于 Ms 温度的 300 °C 等温保温 2 小时，以获得贝氏体显微组织。热处理后的钢材随后进行冷轧和低温轧制（厚度减少 10%）。贝氏体的亚结构由晶包、晶块和亚晶块组成。与未变形状态相比，轧制后贝氏体铁素体的结晶尺寸和微应变都呈下降趋势。然而，低温轧制在保留奥氏体中引起了更高的微应变，这增强了其机械稳定性，需要更高的应力来触发转变诱导塑性（TRIP）效应，从而有助于提高整体强度。晶体学变体分析表明，根据 K-S 取向关系，低温轧制后特定 V1-V3(V5)（高角度嵌段边界）和 V1-V4（亚嵌段边界）变体对的边界密度和频率增加。而热处理后的未变形状态则表现出所有变体，不偏向于任何特定的变体对。结果表明，小冷冻轧制后钢的机械性能受到结晶变体配对和微应变的显著影响。此外，在贝氏体钢中，小冷轧优于冷轧，因为它提高了轧制过程中产生 TRIP 效应所需的阈值应变。
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In this study, we successfully synthesized tetragonal tungsten bronze with the nominal formula Sr2GdTi2Nb3O15 and systematically examined of its structure, dielectric, and electrical properties. The material was synthesized through the solid-state reaction technique at a temperature of 1350 °C. The formation of the tetragonal tungsten bronze in the P4/mbm space group was verified via Rietveld refinement using X-ray diffraction data. The electrical characteristics of the ceramic were examined using non-destructive complex impedance spectroscopy (CIS) across a range of frequencies (10–106 Hz) at various temperatures. The real component of impedance (Z') displayed a decrease with rising frequency, suggesting a negative temperature coefficient of resistance (NTCR) for this sample. The Cole-Cole plot of the compound exhibits two semicircles, with the compound's resistance gradually decreasing as the temperature increased. Moreover, the activation energy (Ea) was found to be approximately 0.9 eV, which confirms that oxygen vacancies are responsible for the observed relaxation behavior. Complex modulus analysis confirmed the presence of non-Debye relaxations. These results contribute to a thorough comprehension of the structural and electrical characteristics of Sr2GdTi2Nb3O15, opening avenues for potential applications in diverse electronic devices.
在这项研究中，我们成功合成了标称式为 Sr2GdTi2Nb3O15 的四方钨青铜，并对其结构、介电性能和电学性能进行了系统研究。该材料是在 1350 °C 温度下通过固态反应技术合成的。利用 X 射线衍射数据通过里特维尔德精炼验证了 P4/mbm 空间群四方钨青铜的形成。在不同温度下，使用非破坏性复阻抗光谱（CIS）在一定频率（10-106 Hz）范围内检测了陶瓷的电气特性。阻抗的实际分量（Z'）随着频率的升高而降低，这表明该样品具有负温度电阻系数（NTCR）。该化合物的科尔-科尔图显示出两个半圆，随着温度的升高，化合物的电阻逐渐减小。此外，还发现活化能（Ea）约为 0.9 eV，这证实了氧空位是造成所观察到的弛豫行为的原因。复模量分析证实了非德拜弛豫的存在。这些结果有助于深入理解 Sr2GdTi2Nb3O15 的结构和电气特性，为其在各种电子设备中的潜在应用开辟了道路。
{"title":"Analysis of the Sr2GdTi2Nb3O15 ceramic: Investigation into its structural properties and complex impedance spectroscopy","authors":"Karim Chourti, Amine Bendahhou, Ilyas Jalafi, Fatima Chaou, Soufian El Barkany, Mohamed Abou-salama","doi":"10.1016/j.mtla.2024.102256","DOIUrl":"10.1016/j.mtla.2024.102256","url":null,"abstract":"<div><div>In this study, we successfully synthesized tetragonal tungsten bronze with the nominal formula Sr<sub>2</sub>GdTi<sub>2</sub>Nb<sub>3</sub>O<sub>15</sub> and systematically examined of its structure, dielectric, and electrical properties. The material was synthesized through the solid-state reaction technique at a temperature of 1350 °C. The formation of the tetragonal tungsten bronze in the <em>P4/mbm</em> space group was verified via Rietveld refinement using X-ray diffraction data. The electrical characteristics of the ceramic were examined using non-destructive complex impedance spectroscopy (CIS) across a range of frequencies (10–10<sup>6</sup> Hz) at various temperatures. The real component of impedance (Z') displayed a decrease with rising frequency, suggesting a negative temperature coefficient of resistance (NTCR) for this sample. The Cole-Cole plot of the compound exhibits two semicircles, with the compound's resistance gradually decreasing as the temperature increased. Moreover, the activation energy (E<sub>a</sub>) was found to be approximately 0.9 eV, which confirms that oxygen vacancies are responsible for the observed relaxation behavior. Complex modulus analysis confirmed the presence of non-Debye relaxations. These results contribute to a thorough comprehension of the structural and electrical characteristics of Sr<sub>2</sub>GdTi<sub>2</sub>Nb<sub>3</sub>O<sub>15</sub>, opening avenues for potential applications in diverse electronic devices.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102256"},"PeriodicalIF":3.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446978","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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