We present the structural, vibrational and luminescence properties of Na- and Li- stabilized gallium–titanium oxides studied by optical spectroscopy techniques. The microstructure and characteristic vibrational modes of this homologous series, which are not well known, have been determined with the aid of Raman spectroscopy and compared to density functional theory (DFT) calculations. On the other hand, intense cathodoluminescence bands in the visible and in the near-infrared are observed depending on the term of the series and related to native defects. Besides, the study of the temperature evolution of the photoluminescence and photoluminescence excitation spectra has allowed us to determine both the band gap energy temperature dependence as well as to get some insight into the luminescence mechanisms of the defect-related emissions in these compounds. The results pave the way to exploit the physical properties of these Na- and Li-gallium titanate series in functional optoelectronic devices to operate from the ultraviolet to the infrared range.
{"title":"Study of the microstructure and temperature dependent luminescence of Na- and Li-beta gallia rutile compounds","authors":"Marina García-Carrión, Ruth Martínez-Casado, Emilio Nogales, Bianchi Méndez","doi":"10.1016/j.mtla.2024.102302","DOIUrl":"10.1016/j.mtla.2024.102302","url":null,"abstract":"<div><div>We present the structural, vibrational and luminescence properties of Na- and Li- stabilized gallium–titanium oxides studied by optical spectroscopy techniques. The microstructure and characteristic vibrational modes of this homologous series, which are not well known, have been determined with the aid of Raman spectroscopy and compared to density functional theory (DFT) calculations. On the other hand, intense cathodoluminescence bands in the visible and in the near-infrared are observed depending on the term of the series and related to native defects. Besides, the study of the temperature evolution of the photoluminescence and photoluminescence excitation spectra has allowed us to determine both the band gap energy temperature dependence as well as to get some insight into the luminescence mechanisms of the defect-related emissions in these compounds. The results pave the way to exploit the physical properties of these Na- and Li-gallium titanate series in functional optoelectronic devices to operate from the ultraviolet to the infrared range.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102302"},"PeriodicalIF":3.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143168109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-01DOI: 10.1016/j.mtla.2024.102266
N.L. Church, J.Y. Ang, O.G. Reed, O.E. Gibson, N.G. Jones
Ti-Nb based alloys are candidate materials for orthopaedic and orthodontic applications due to a low elastic modulus and superelastic properties. However, many of these alloys are also susceptible to a transformation to the hexagonal ⍵ phase. When ⍵ is formed isothermally it can stiffen and embrittle the alloy, however, there is a limited understanding of the role it plays when formed athermally on cooling, with many conflicting statements made within the literature. As such, this study assesses the role of athermally formed ⍵ on the superelastic behaviour and elastic modulus of the exemplar superelastic alloy, Ti-24Nb-4Zr-8Sn. It was found that the ⍵ phase raised the modulus and the stress required for superelastic behaviour. This highlights the need to design alloys resistant to both forms of the ⍵ phase, for low modulus superelastic alloys to be produced.
{"title":"The effect of athermal omega on the transformation behaviour of Ti-24Nb-4Zr-8Sn (wt%)","authors":"N.L. Church, J.Y. Ang, O.G. Reed, O.E. Gibson, N.G. Jones","doi":"10.1016/j.mtla.2024.102266","DOIUrl":"10.1016/j.mtla.2024.102266","url":null,"abstract":"<div><div>Ti-Nb based alloys are candidate materials for orthopaedic and orthodontic applications due to a low elastic modulus and superelastic properties. However, many of these alloys are also susceptible to a transformation to the hexagonal ⍵ phase. When ⍵ is formed isothermally it can stiffen and embrittle the alloy, however, there is a limited understanding of the role it plays when formed athermally on cooling, with many conflicting statements made within the literature. As such, this study assesses the role of athermally formed ⍵ on the superelastic behaviour and elastic modulus of the exemplar superelastic alloy, Ti-24Nb-4Zr-8Sn. It was found that the ⍵ phase raised the modulus and the stress required for superelastic behaviour. This highlights the need to design alloys resistant to both forms of the ⍵ phase, for low modulus superelastic alloys to be produced.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102266"},"PeriodicalIF":3.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143168108","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 : 2024-11-30DOI: 10.1016/j.mtla.2024.102308
Karline Pascaud , Christophe Tenailleau , Benjamin Duployer , Romain Sescousse , Fabien Brouillet , Cristiano C. Jayme , Daniela S. Fernandes , Antonio C. Tedesco , Stéphanie Sarda , Maria Ines Ré
Synthetic apatitic calcium phosphates are widely used to develop biomaterial devices due to their excellent biological properties. The aim of this study was to develop nanocrystalline apatitic calcium phosphates (NCA) bioceramics with tunable porosity (size of pores, total porosity percent) to preserve surface reactivity and improve bioactivity based on an original manufacturing process. For this purpose, a low-temperature method of elaboration via Pickering emulsions was used and the influence of several process parameters (emulsion-to-gel weight ratio and formulation of the emulsion) on the properties of the bioceramics was studied. This process allows the formation of NCA crystals–based materials as shown by X-ray diffraction and FTIR spectroscopy. The initial conditions of the emulsion control the final porous structure evidenced by X-ray micro-computed tomography: if the diameter of the droplets of the starting emulsions controls the pores size, it does not influence the total porosity percent and interconnection which depend only on the emulsion-to-gel ratio. The viability of the scaffolds was assessed using the osteoblast cell line in two steps: cell adhesion assays and photobiomodulation. None of the scaffolds showed cytotoxic effects. With the proposed process, scaffolds were obtained with controlled pore size and interconnected pores, composed of reactive biomimetic apatites with mechanical properties suitable for applications in filling bone defects and good osteoblastic adhesion and proliferation properties.
{"title":"Achieving tunable and interconnected porosity of biomimetic apatite scaffolds through Pickering emulsion templates","authors":"Karline Pascaud , Christophe Tenailleau , Benjamin Duployer , Romain Sescousse , Fabien Brouillet , Cristiano C. Jayme , Daniela S. Fernandes , Antonio C. Tedesco , Stéphanie Sarda , Maria Ines Ré","doi":"10.1016/j.mtla.2024.102308","DOIUrl":"10.1016/j.mtla.2024.102308","url":null,"abstract":"<div><div>Synthetic apatitic calcium phosphates are widely used to develop biomaterial devices due to their excellent biological properties. The aim of this study was to develop nanocrystalline apatitic calcium phosphates (NCA) bioceramics with tunable porosity (size of pores, total porosity percent) to preserve surface reactivity and improve bioactivity based on an original manufacturing process. For this purpose, a low-temperature method of elaboration via Pickering emulsions was used and the influence of several process parameters (emulsion-to-gel weight ratio and formulation of the emulsion) on the properties of the bioceramics was studied. This process allows the formation of NCA crystals–based materials as shown by X-ray diffraction and FTIR spectroscopy. The initial conditions of the emulsion control the final porous structure evidenced by X-ray micro-computed tomography: if the diameter of the droplets of the starting emulsions controls the pores size, it does not influence the total porosity percent and interconnection which depend only on the emulsion-to-gel ratio. The viability of the scaffolds was assessed using the osteoblast cell line in two steps: cell adhesion assays and photobiomodulation. None of the scaffolds showed cytotoxic effects. With the proposed process, scaffolds were obtained with controlled pore size and interconnected pores, composed of reactive biomimetic apatites with mechanical properties suitable for applications in filling bone defects and good osteoblastic adhesion and proliferation properties.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102308"},"PeriodicalIF":3.0,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173184","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}
Unnotched and notched tensile properties of Ti-6Al-4V (Ti64) alloy, additively manufactured using the laser powder bed fusion (LPBF) technique, at cryogenic temperatures of 90, 77 and 20 K were investigated. The LPBF process parameter combination was chosen such that the investigated alloy has not only a minimum in porosity, but also an equiaxed prior β microstructure, which predominantly contains acicular α/α’ lath structure in basket-weave morphology, that results in a high strength and ductility combination as well as insignificant mechanical anisotropy at room temperature (300 K). Tensile tests revealed that the yield (σy) and tensile (σu) strengths of LPBF Ti64 are superior while elongation to failure (ef) is comparable to those of the conventionally manufactured (CM) Ti64 down to 77 K, owing to the fine α/α’ lath microstructure in the former. While the progressive reduction of <a>-basal and prismatic dislocation slip activity with decreasing deformation temperature enables a steep rise in σy, the unnotched specimens fractured catastrophically without macroscopic yielding at 20 K. Detailed postmortem analyses revealed the absence of significant twinning-based deformation in LPBF Ti64, in stark contrast to the CM ones at cryogenic temperatures. Instead, deformation kink bands with varying sizes and misorientation were found to be increasingly active within the prior β grains. A large misorientation at the kink band boundary within the β grain leads to void nucleation followed by crack growth, which eventually results in brittle failure at 20 K. While relatively notch insensitive from 300 to 77 K, LPBF Ti64 was notch brittle at 20 K. These results highlight the importance of the unique hierarchical micro- and meso‑structural features of LPBF Ti64 on the tensile mechanical behavior, especially at cryogenic temperatures.
{"title":"Cryogenic temperature tensile properties of laser powder bed fused Ti-6Al-4V","authors":"Jayaraj Radhakrishnan , Gaurav Singh , Punit Kumar , Niraj Nayan , Upadrasta Ramamurty","doi":"10.1016/j.mtla.2024.102307","DOIUrl":"10.1016/j.mtla.2024.102307","url":null,"abstract":"<div><div>Unnotched and notched tensile properties of Ti-6Al-4V (Ti64) alloy, additively manufactured using the laser powder bed fusion (LPBF) technique, at cryogenic temperatures of 90, 77 and 20 K were investigated. The LPBF process parameter combination was chosen such that the investigated alloy has not only a minimum in porosity, but also an equiaxed prior β microstructure, which predominantly contains acicular α/α’ lath structure in basket-weave morphology, that results in a high strength and ductility combination as well as insignificant mechanical anisotropy at room temperature (300 K). Tensile tests revealed that the yield (<em>σ</em><sub>y</sub>) and tensile (<em>σ</em><sub>u</sub>) strengths of LPBF Ti64 are superior while elongation to failure (<em>e</em><sub>f</sub>) is comparable to those of the conventionally manufactured (CM) Ti64 down to 77 K, owing to the fine α/α’ lath microstructure in the former. While the progressive reduction of <<em>a</em>>-basal and prismatic dislocation slip activity with decreasing deformation temperature enables a steep rise in <em>σ</em><sub>y</sub>, the unnotched specimens fractured catastrophically without macroscopic yielding at 20 K. Detailed postmortem analyses revealed the absence of significant twinning-based deformation in LPBF Ti64, in stark contrast to the CM ones at cryogenic temperatures. Instead, deformation kink bands with varying sizes and misorientation were found to be increasingly active within the prior β grains. A large misorientation at the kink band boundary within the β grain leads to void nucleation followed by crack growth, which eventually results in brittle failure at 20 K. While relatively notch insensitive from 300 to 77 K, LPBF Ti64 was notch brittle at 20 K. These results highlight the importance of the unique hierarchical micro- and meso‑structural features of LPBF Ti64 on the tensile mechanical behavior, especially at cryogenic temperatures.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"39 ","pages":"Article 102307"},"PeriodicalIF":3.0,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173183","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 : 2024-11-24DOI: 10.1016/j.mtla.2024.102301
Louis Hennocque , Julien Favre , Nicolas Meyer , Thomas Sourisseau , David Piot , Frank Montheillet , Laurence Latu-Romain , Guillaume Kermouche
The mechanisms of nucleation during dynamic and static recrystallization still remain unclear, particularly with respect to their precise formulation into equations, and the specific implications of subgrains features on these mechanisms. In this paper, it is proposed to correlate the grain nucleation with subgrains and low-angle boundaries misorientation evolution. A nucleation criterion that takes into account the low-angle boundary density evolution in the system is established based on thermodynamic considerations. This new approach is based on a reformulation of the Bailey-Hirsch criterion and is derived from calculations of the equilibrium pressure on grain boundaries. The free energy calculations associated with this criterion allow a fine phenomenological description of the associated nucleation frequency. This new approach is tested in the case of recrystallization of a ferritic stainless steel grade during hot compression tests. The evolution of the substructure is then studied for different holding times up to 20 s after hot compression. It appears that the nucleation frequency based on the proposed nucleation criterion is in agreement with the nucleation frequency derived from experimental observations. This approach allows a better understanding of the mechanisms governing the ability of a subgrain to nucleate in a given system, using rather simple assumptions.
{"title":"Nucleation of recrystallization: A new approach to consider the evolution of the substructure in the system","authors":"Louis Hennocque , Julien Favre , Nicolas Meyer , Thomas Sourisseau , David Piot , Frank Montheillet , Laurence Latu-Romain , Guillaume Kermouche","doi":"10.1016/j.mtla.2024.102301","DOIUrl":"10.1016/j.mtla.2024.102301","url":null,"abstract":"<div><div>The mechanisms of nucleation during dynamic and static recrystallization still remain unclear, particularly with respect to their precise formulation into equations, and the specific implications of subgrains features on these mechanisms. In this paper, it is proposed to correlate the grain nucleation with subgrains and low-angle boundaries misorientation evolution. A nucleation criterion that takes into account the low-angle boundary density evolution in the system is established based on thermodynamic considerations. This new approach is based on a reformulation of the Bailey-Hirsch criterion and is derived from calculations of the equilibrium pressure on grain boundaries. The free energy calculations associated with this criterion allow a fine phenomenological description of the associated nucleation frequency. This new approach is tested in the case of recrystallization of a ferritic stainless steel grade during hot compression tests. The evolution of the substructure is then studied for different holding times up to 20 s after hot compression. It appears that the nucleation frequency based on the proposed nucleation criterion is in agreement with the nucleation frequency derived from experimental observations. This approach allows a better understanding of the mechanisms governing the ability of a subgrain to nucleate in a given system, using rather simple assumptions.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102301"},"PeriodicalIF":3.0,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720120","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 : 2024-11-23DOI: 10.1016/j.mtla.2024.102294
Meiling Li , Mingwei Hu , Yaning Wang , Yonghui Ma , Yi Yuan , Tahashi Masahiro , Qiang Wang
This study reports a significant enhancement of the thermoelectric properties of Bi2Te3-based materials achieved by modifying their internal microstructure via the high magnetic field-directed solidification method. The magnetic moment generated by the magnetic field leads to an optimal crystal orientation, drastically reducing the resistivity while maintaining the stability of the Seebeck coefficient. Consequently, the power factors of P-type Bi0.5Sb1.5Te3 and N-type Bi2Te3 samples were improved by 29.2 and 23.2 %, respectively. Furthermore, the thermoelectric magnetic force by the high magnetic field serves to refine the grain size and augment the source of phonon scatting, which effectively reduces the lattice thermal conductivity. Eventually, the zTMax of the P-type Bi0.5Sb1.5Te3 sample reaches 1.12, while that of the N-type Bi2Te3 sample is 0.24, both higher than the value without the high magnetic field.
{"title":"Thermoelectric properties of Bi2Te3-based prepared by directional solidification under a high magnetic field","authors":"Meiling Li , Mingwei Hu , Yaning Wang , Yonghui Ma , Yi Yuan , Tahashi Masahiro , Qiang Wang","doi":"10.1016/j.mtla.2024.102294","DOIUrl":"10.1016/j.mtla.2024.102294","url":null,"abstract":"<div><div>This study reports a significant enhancement of the thermoelectric properties of Bi<sub>2</sub>Te<sub>3</sub>-based materials achieved by modifying their internal microstructure via the high magnetic field-directed solidification method. The magnetic moment generated by the magnetic field leads to an optimal crystal orientation, drastically reducing the resistivity while maintaining the stability of the Seebeck coefficient. Consequently, the power factors of P-type Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> and N-type Bi<sub>2</sub>Te<sub>3</sub> samples were improved by 29.2 and 23.2 %, respectively. Furthermore, the thermoelectric magnetic force by the high magnetic field serves to refine the grain size and augment the source of phonon scatting, which effectively reduces the lattice thermal conductivity. Eventually, the <em>zT</em><sub>Max</sub> of the P-type Bi<sub>0.5</sub>Sb<sub>1.5</sub>Te<sub>3</sub> sample reaches 1.12, while that of the N-type Bi<sub>2</sub>Te<sub>3</sub> sample is 0.24, both higher than the value without the high magnetic field.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102294"},"PeriodicalIF":3.0,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720117","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 : 2024-11-22DOI: 10.1016/j.mtla.2024.102298
Punnathat Bordeenithikasem, Richard Otis, Miguel B. Costa, Douglas C. Hofmann, R. Peter Dillon
Bulk metallic glasses (BMGs) are multi-element metal alloys with attractive properties for spacecraft applications. With recent advances in the BMG supply chain and commercialization, understanding the effects of thermal history associated with the manufacturing, integration, and service on performance of BMG components is critical for infusion. In this study, a Cu43Zr43Al7Be7 (at. %) BMG-forming composition, an alloy developed for gears for extreme-environment applications, was investigated. The thermal properties and structural glassy states resulting from different thermal treatments were studied with differential scanning calorimetry, microhardness, and four-point bending tests. It is shown that the thermal history and resulting structural states have a pronounced effect on some mechanical properties, highlighting the necessity of qualifying parts in different glassy states for their intended practical applications.
{"title":"Effect of thermal history on performance of bulk metallic glass spacecraft components","authors":"Punnathat Bordeenithikasem, Richard Otis, Miguel B. Costa, Douglas C. Hofmann, R. Peter Dillon","doi":"10.1016/j.mtla.2024.102298","DOIUrl":"10.1016/j.mtla.2024.102298","url":null,"abstract":"<div><div>Bulk metallic glasses (BMGs) are multi-element metal alloys with attractive properties for spacecraft applications. With recent advances in the BMG supply chain and commercialization, understanding the effects of thermal history associated with the manufacturing, integration, and service on performance of BMG components is critical for infusion. In this study, a Cu<sub>43</sub>Zr<sub>43</sub>Al<sub>7</sub>Be<sub>7</sub> (at. %) BMG-forming composition, an alloy developed for gears for extreme-environment applications, was investigated. The thermal properties and structural glassy states resulting from different thermal treatments were studied with differential scanning calorimetry, microhardness, and four-point bending tests. It is shown that the thermal history and resulting structural states have a pronounced effect on some mechanical properties, highlighting the necessity of qualifying parts in different glassy states for their intended practical applications.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102298"},"PeriodicalIF":3.0,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720118","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}
Semi-solid deformation is a versatile phenomenon that occurs during the solidification of alloys. Semi-solid simple shear deformation is simulated using the multi-phase-field lattice Boltzmann (MPF-LB) method, which has been originally devised to capture polycrystalline solidification accompanied with melt flow and solid motion. MPF-LB simulations of semi-solid simple shear deformation, with variations in solid fractions, reveal the transition from a liquid-like behavior to a solid-like one. Especially, the shear band formed via dilatancy effects is thoroughly examined in the high solid fraction region. The relationship between grain rearrangement and mechanical behaviors during the formation process of the shear band is investigated in detail. In addition, the effect of domain size and initial grain arrangement on shear band formation is evaluated. Finally, the mechanism of shear band formation is clarified. The developed MPF-LB simulation method is promising for comprehensive evaluations of semi-solid deformation.
{"title":"Multi-phase-field lattice Boltzmann modeling and simulations of semi-solid simple shear deformation","authors":"Namito Yamanaka , Shinmei Hayase , Shinji Sakane , Tomohiro Takaki","doi":"10.1016/j.mtla.2024.102295","DOIUrl":"10.1016/j.mtla.2024.102295","url":null,"abstract":"<div><div>Semi-solid deformation is a versatile phenomenon that occurs during the solidification of alloys. Semi-solid simple shear deformation is simulated using the multi-phase-field lattice Boltzmann (MPF-LB) method, which has been originally devised to capture polycrystalline solidification accompanied with melt flow and solid motion. MPF-LB simulations of semi-solid simple shear deformation, with variations in solid fractions, reveal the transition from a liquid-like behavior to a solid-like one. Especially, the shear band formed via dilatancy effects is thoroughly examined in the high solid fraction region. The relationship between grain rearrangement and mechanical behaviors during the formation process of the shear band is investigated in detail. In addition, the effect of domain size and initial grain arrangement on shear band formation is evaluated. Finally, the mechanism of shear band formation is clarified. The developed MPF-LB simulation method is promising for comprehensive evaluations of semi-solid deformation.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102295"},"PeriodicalIF":3.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142700376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.mtla.2024.102297
Jacob Elms , Alison Pawley , Nicholas Bojdo , Stephen Covey-Crump , Merren Jones , Rory Clarkson
Civil aircraft engines ingest significant quantities of mineral dusts during their operation in arid regions. These deposit on the engine components, melt at the elevated operating temperatures, and cause damage to the insulative Thermal Barrier Coatings (TBCs) that are critical to the durability of high temperature engine components. New melt-resistant TBCs may only mitigate damage effectively for specific deposit chemistries. We have investigated the use of tailored additives to change a deposit composition, raise its melting point and prevent melt formation. Only CaO-MgO-Al2O3-SiO2 (CMAS) compositions were explored because deposits are typically simplified to this system. For our approach to work, it must be possible to reliably predict the composition, amount and melting temperatures of the deposited material and additive required to prevent melt formation at a given temperature. Experiments were performed between 1200 and 1400°C to investigate the chemistry and melting temperatures of a ‘deposit’ CMAS composition, and two ‘deposit + additives’ CMAS compositions produced by adding dolomite (CaMg[CO3]2) and/or periclase (MgO) to the ‘deposit’. We observed that enriching the starting material in CaO and MgO increased its melting temperature such that little to no melt would form on a high pressure turbine blade. Deviations of our liquidus temperatures from published liquidus diagrams show the need for further refinement of sections of the phase diagram. Greater understanding of the composition of airborne dusts around the world and their evolution inside aircraft engines is necessary before this approach can be used in practice.
{"title":"Tailored geochemical additives to inhibit CaO-MgO-Al2O3-SiO2 (CMAS) melt formation in gas turbine engines","authors":"Jacob Elms , Alison Pawley , Nicholas Bojdo , Stephen Covey-Crump , Merren Jones , Rory Clarkson","doi":"10.1016/j.mtla.2024.102297","DOIUrl":"10.1016/j.mtla.2024.102297","url":null,"abstract":"<div><div>Civil aircraft engines ingest significant quantities of mineral dusts during their operation in arid regions. These deposit on the engine components, melt at the elevated operating temperatures, and cause damage to the insulative Thermal Barrier Coatings (TBCs) that are critical to the durability of high temperature engine components. New melt-resistant TBCs may only mitigate damage effectively for specific deposit chemistries. We have investigated the use of tailored additives to change a deposit composition, raise its melting point and prevent melt formation. Only CaO-MgO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> (CMAS) compositions were explored because deposits are typically simplified to this system. For our approach to work, it must be possible to reliably predict the composition, amount and melting temperatures of the deposited material and additive required to prevent melt formation at a given temperature. Experiments were performed between 1200 and 1400°C to investigate the chemistry and melting temperatures of a ‘deposit’ CMAS composition, and two ‘deposit + additives’ CMAS compositions produced by adding dolomite (CaMg[CO<sub>3</sub>]<sub>2</sub>) and/or periclase (MgO) to the ‘deposit’. We observed that enriching the starting material in CaO and MgO increased its melting temperature such that little to no melt would form on a high pressure turbine blade. Deviations of our liquidus temperatures from published liquidus diagrams show the need for further refinement of sections of the phase diagram. Greater understanding of the composition of airborne dusts around the world and their evolution inside aircraft engines is necessary before this approach can be used in practice.</div></div>","PeriodicalId":47623,"journal":{"name":"Materialia","volume":"38 ","pages":"Article 102297"},"PeriodicalIF":3.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720116","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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