Pub Date : 2021-07-03DOI: 10.1080/09500839.2021.1917780
Ke-wei Zhang, X. Ji, Y. Mi, Lei Gao, Tianyu Wang
ABSTRACT A series of polytetrafluoroethylene (PTFE) composites filled with CF (carbon fiber) and MoS2 (molybdenum disulfide) were prepared by cold-pressing sintering. The tensile strength and elongation at the breakpoint of the samples were measured with a bench-top tensile machine, friction and wear performance were tested with an abrasion machine, and the morphology and microscopic structure were analysed by SEM. The results show that the tensile strength, the elongation at breakage, and the wear resistance were all improved after filling compared to the pure PTFE. The CF/MoS2/PTFE composites filled with CF (particle size 7.498 μm) had the optimal tensile strength and elongation at the breakpoint. Correspondingly, the wear rate was the smallest when the particle size was 23.733 μm.
{"title":"Effects of carbon fibers with different particle sizes on the physical properties of MoS2-filled PTFE composites","authors":"Ke-wei Zhang, X. Ji, Y. Mi, Lei Gao, Tianyu Wang","doi":"10.1080/09500839.2021.1917780","DOIUrl":"https://doi.org/10.1080/09500839.2021.1917780","url":null,"abstract":"ABSTRACT A series of polytetrafluoroethylene (PTFE) composites filled with CF (carbon fiber) and MoS2 (molybdenum disulfide) were prepared by cold-pressing sintering. The tensile strength and elongation at the breakpoint of the samples were measured with a bench-top tensile machine, friction and wear performance were tested with an abrasion machine, and the morphology and microscopic structure were analysed by SEM. The results show that the tensile strength, the elongation at breakage, and the wear resistance were all improved after filling compared to the pure PTFE. The CF/MoS2/PTFE composites filled with CF (particle size 7.498 μm) had the optimal tensile strength and elongation at the breakpoint. Correspondingly, the wear rate was the smallest when the particle size was 23.733 μm.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"277 - 286"},"PeriodicalIF":1.2,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1917780","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44406454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-06-22DOI: 10.1080/09500839.2021.1937367
J. Chakraborty
ABSTRACT Crystallite-size-dependent lattice expansion of the hcp Ti phase has been observed by X-ray diffraction of polycrystalline Ti thin films. X-ray line profile analysis (XLPA) revealed a systematic reduction of crystallite size in the hcp Ti phase with decreasing film thickness. Increase of specific volume (i.e. volume/atom) of the hcp Ti phase with decreasing crystallite size has confirmed such lattice expansion. The observed lattice expansion has been simulated using an existing theoretical model after appropriately incorporating a crystallite-size-dependent width of the grain boundaries. It is further revealed that decreasing crystallite size and accompanying lattice expansion leads to lattice instability of the hcp Ti phase and eventually to a hcp-fcc phase transformation of elemental Ti in these thin films as reported earlier by the author.
{"title":"Lattice expansion and phase stability in nanocrystalline titanium thin films","authors":"J. Chakraborty","doi":"10.1080/09500839.2021.1937367","DOIUrl":"https://doi.org/10.1080/09500839.2021.1937367","url":null,"abstract":"ABSTRACT Crystallite-size-dependent lattice expansion of the hcp Ti phase has been observed by X-ray diffraction of polycrystalline Ti thin films. X-ray line profile analysis (XLPA) revealed a systematic reduction of crystallite size in the hcp Ti phase with decreasing film thickness. Increase of specific volume (i.e. volume/atom) of the hcp Ti phase with decreasing crystallite size has confirmed such lattice expansion. The observed lattice expansion has been simulated using an existing theoretical model after appropriately incorporating a crystallite-size-dependent width of the grain boundaries. It is further revealed that decreasing crystallite size and accompanying lattice expansion leads to lattice instability of the hcp Ti phase and eventually to a hcp-fcc phase transformation of elemental Ti in these thin films as reported earlier by the author.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"330 - 340"},"PeriodicalIF":1.2,"publicationDate":"2021-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1937367","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44810795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-06-07DOI: 10.1080/09500839.2021.1936257
K. Osintsev, S. Konovalov, V. Gromov, I. Panchenko, Y. Ivanov
ABSTRACT Gas metal arc welding based on wire arc additive manufacturing was adopted to fabricate a non-equiatomic Al2.1Co0.3Cr0.5FeNi2.1 thick-walled component. The combined cable wire composed of three filaments with different elemental compositions was used as the feeding material. The microstructure and mechanical properties of the as-deposited component were investigated. The deposited sample consisted of dendrite grains ranging in size from 5 to 15 µm and interdendritic regions. The compressive yield strength and ultimate compressive strength of the obtained material are 550 and 1899 MPa. The microhardness test revealed an average value of 463 HV. The nanohardness and the elastic modulus of the sample are 10.4 and 304 GPa, respectively. Energy-dispersive spectroscopy showed that the elemental distribution in the top, middle, and bottom areas of the sample is uniform. X-ray diffraction analysis revealed two main phases of Al-Ni-Co-rich B2 and Fe-Cr-rich A2 in the material.
{"title":"Microstructural and mechanical characterisation of non-equiatomic Al2.1Co0.3Cr0.5FeNi2.1 high-entropy alloy fabricated via wire-arc additive manufacturing","authors":"K. Osintsev, S. Konovalov, V. Gromov, I. Panchenko, Y. Ivanov","doi":"10.1080/09500839.2021.1936257","DOIUrl":"https://doi.org/10.1080/09500839.2021.1936257","url":null,"abstract":"ABSTRACT Gas metal arc welding based on wire arc additive manufacturing was adopted to fabricate a non-equiatomic Al2.1Co0.3Cr0.5FeNi2.1 thick-walled component. The combined cable wire composed of three filaments with different elemental compositions was used as the feeding material. The microstructure and mechanical properties of the as-deposited component were investigated. The deposited sample consisted of dendrite grains ranging in size from 5 to 15 µm and interdendritic regions. The compressive yield strength and ultimate compressive strength of the obtained material are 550 and 1899 MPa. The microhardness test revealed an average value of 463 HV. The nanohardness and the elastic modulus of the sample are 10.4 and 304 GPa, respectively. Energy-dispersive spectroscopy showed that the elemental distribution in the top, middle, and bottom areas of the sample is uniform. X-ray diffraction analysis revealed two main phases of Al-Ni-Co-rich B2 and Fe-Cr-rich A2 in the material.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"353 - 359"},"PeriodicalIF":1.2,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1936257","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48030948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-06-07DOI: 10.1080/09500839.2021.1936258
B. He, X. Shang
ABSTRACT In general, the formation of martensite in the metastable austenite grains in steels during nanoindentation investigations is believed to be induced by strain as the plastic deformation of austenite takes place prior to the martensitic transformation. However, it is not clear whether the formation of martensite occurs without the prior initiation of plasticity (stress-induced martensitic transformation) during nanoindentation measurement. The present work demonstrates that the martensitic transformation can be triggered during elastic deformation of austenite under an ultralow load when the indenter is close to the annealing twin boundaries. The indentation pressure interacts with the martensite transformation strain, providing the mechanical interaction energy to overcome the nucleation barrier of the martensite embryo. The present work suggests that the annealing twin boundaries can also serve as the nucleation sites of martensite and the stress-induced martensitic transformation is possible during nanoindentation investigation.
{"title":"Stress-induced martensitic transformation in metastable austenite grains during nanoindentation investigation","authors":"B. He, X. Shang","doi":"10.1080/09500839.2021.1936258","DOIUrl":"https://doi.org/10.1080/09500839.2021.1936258","url":null,"abstract":"ABSTRACT In general, the formation of martensite in the metastable austenite grains in steels during nanoindentation investigations is believed to be induced by strain as the plastic deformation of austenite takes place prior to the martensitic transformation. However, it is not clear whether the formation of martensite occurs without the prior initiation of plasticity (stress-induced martensitic transformation) during nanoindentation measurement. The present work demonstrates that the martensitic transformation can be triggered during elastic deformation of austenite under an ultralow load when the indenter is close to the annealing twin boundaries. The indentation pressure interacts with the martensite transformation strain, providing the mechanical interaction energy to overcome the nucleation barrier of the martensite embryo. The present work suggests that the annealing twin boundaries can also serve as the nucleation sites of martensite and the stress-induced martensitic transformation is possible during nanoindentation investigation.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"417 - 431"},"PeriodicalIF":1.2,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1936258","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46655768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-06-03DOI: 10.1080/09500839.2021.1909166
Alexandre Mathevon, M. Perez, V. Massardier, D. Fabrègue, P. Chantrenne, P. Rocabois
ABSTRACT A new model has been developed to predict austenite ferrite transformation kinetics in steels. For each alloying element, the concentration profile is computed solving a unique diffusion equation (including the 2 phases and the interface). The interface is described assuming linear variation of chemical potentials, saving thus computational time. Interface motion is driven by the minimisation of Gibbs energy. The model naturally reproduces the transition between thermodynamic equilibria (Para equilibrium, Local equilibrium with negligible partitioning, Local equilibrium) during heating. The validity of the model for reverse transformation has been validated on ternary and quaternary systems Fe-C-(Mn-Si-Mo) on decarburisation experiments.
{"title":"Gibbs energy minimisation model for the austenite-ferrite phase transformation in Fe-C-X-Y alloys","authors":"Alexandre Mathevon, M. Perez, V. Massardier, D. Fabrègue, P. Chantrenne, P. Rocabois","doi":"10.1080/09500839.2021.1909166","DOIUrl":"https://doi.org/10.1080/09500839.2021.1909166","url":null,"abstract":"ABSTRACT A new model has been developed to predict austenite ferrite transformation kinetics in steels. For each alloying element, the concentration profile is computed solving a unique diffusion equation (including the 2 phases and the interface). The interface is described assuming linear variation of chemical potentials, saving thus computational time. Interface motion is driven by the minimisation of Gibbs energy. The model naturally reproduces the transition between thermodynamic equilibria (Para equilibrium, Local equilibrium with negligible partitioning, Local equilibrium) during heating. The validity of the model for reverse transformation has been validated on ternary and quaternary systems Fe-C-(Mn-Si-Mo) on decarburisation experiments.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"232 - 241"},"PeriodicalIF":1.2,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1909166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49647475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-06-03DOI: 10.1080/09500839.2021.1933641
Cheng Xie, He Zhao, L. Du, H. Du, Pingping Wu
ABSTRACT Porous ferroelectric materials show great potential for achieving competitive dielectric/piezoelectric properties with light weight. In this study, a phase-field model was employed to simulate the ferroelectric domain structure evolution of porous barium titanate. It is suggested that the ferroelectric/dielectric/piezoelectric properties are strongly influenced by the porosity level and the size of pores for porous ceramics. It is demonstrated that the ferroelectric switching behaviour, the remnant polarisation, the dielectric constant and the piezoelectric constant are enhanced in nanoporous ferroelectrics with ellipse-shaped pores by introducing mechanisms of symmetry breaking. By providing a means of achieving enhanced properties, nanoporous ferroelectrics with ellipse-shaped pores may have a broad impact on the applications of ferroelectrics and enhance the utility of the materials for selected applications.
{"title":"Enhanced ferroelectricity for nanoporous barium titanate: a phase-field prediction","authors":"Cheng Xie, He Zhao, L. Du, H. Du, Pingping Wu","doi":"10.1080/09500839.2021.1933641","DOIUrl":"https://doi.org/10.1080/09500839.2021.1933641","url":null,"abstract":"ABSTRACT Porous ferroelectric materials show great potential for achieving competitive dielectric/piezoelectric properties with light weight. In this study, a phase-field model was employed to simulate the ferroelectric domain structure evolution of porous barium titanate. It is suggested that the ferroelectric/dielectric/piezoelectric properties are strongly influenced by the porosity level and the size of pores for porous ceramics. It is demonstrated that the ferroelectric switching behaviour, the remnant polarisation, the dielectric constant and the piezoelectric constant are enhanced in nanoporous ferroelectrics with ellipse-shaped pores by introducing mechanisms of symmetry breaking. By providing a means of achieving enhanced properties, nanoporous ferroelectrics with ellipse-shaped pores may have a broad impact on the applications of ferroelectrics and enhance the utility of the materials for selected applications.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"341 - 352"},"PeriodicalIF":1.2,"publicationDate":"2021-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1933641","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44380915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-04-28DOI: 10.1080/09500839.2021.1917781
A. Ghorai
ABSTRACT Parameters of the Ashcroft and Heine–Abarenkov model potential have been computed for face-centred cubic (fcc) actinium (Ac) crystal. The calculation uses the pseudopotential technique with nine different exchange and correlation functions and an empirical relation based on other experimental parameters, namely, the melting temperature and the cohesive energy. The complete set of values for this parameter will be used for future calculations of self-diffusion and impurity diffusion via a vacancy mechanism or via other types of defects.
{"title":"Calculation of parameters of the Ashcroft and Heine–Abarenkov model potential for fcc actinium","authors":"A. Ghorai","doi":"10.1080/09500839.2021.1917781","DOIUrl":"https://doi.org/10.1080/09500839.2021.1917781","url":null,"abstract":"ABSTRACT Parameters of the Ashcroft and Heine–Abarenkov model potential have been computed for face-centred cubic (fcc) actinium (Ac) crystal. The calculation uses the pseudopotential technique with nine different exchange and correlation functions and an empirical relation based on other experimental parameters, namely, the melting temperature and the cohesive energy. The complete set of values for this parameter will be used for future calculations of self-diffusion and impurity diffusion via a vacancy mechanism or via other types of defects.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"287 - 292"},"PeriodicalIF":1.2,"publicationDate":"2021-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1917781","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47124026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-04-14DOI: 10.1080/09500839.2021.1912426
S. Kashyap, R. Mitra
ABSTRACT The ZrB2–SiC–LaB6 composite prepared by spark plasma sintering with B4C and C as additives was isothermally exposed in air at 1500°C for 24 h and the evolved oxide scale examined by scanning and transmission electron microscopy. It was found that a glassy borosilicate (BSG) layer with a thin film of La2Si2O7 had formed on the outermost surface of oxide scale, contributing to protection against oxidation. The detailed investigation of the cross-section of the oxide scale has revealed the formation of a layered microstructure formed by growth involving partial crystallisation of BSG forming ZrSiO4 along with re-precipitation of La2Si2O7 and ZrO2 after prior dissolution of La2O3 and ZrO2 in the glassy matrix.
{"title":"Microstructure and composition of multi-layered oxide scale evolved during isothermal exposure of ZrB2–SiC–LaB6 composite to air at 1500°C","authors":"S. Kashyap, R. Mitra","doi":"10.1080/09500839.2021.1912426","DOIUrl":"https://doi.org/10.1080/09500839.2021.1912426","url":null,"abstract":"ABSTRACT The ZrB2–SiC–LaB6 composite prepared by spark plasma sintering with B4C and C as additives was isothermally exposed in air at 1500°C for 24 h and the evolved oxide scale examined by scanning and transmission electron microscopy. It was found that a glassy borosilicate (BSG) layer with a thin film of La2Si2O7 had formed on the outermost surface of oxide scale, contributing to protection against oxidation. The detailed investigation of the cross-section of the oxide scale has revealed the formation of a layered microstructure formed by growth involving partial crystallisation of BSG forming ZrSiO4 along with re-precipitation of La2Si2O7 and ZrO2 after prior dissolution of La2O3 and ZrO2 in the glassy matrix.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"265 - 276"},"PeriodicalIF":1.2,"publicationDate":"2021-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1912426","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48304858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2021-04-09DOI: 10.1080/09500839.2021.1910745
Xiangwei Kong, Weiqiang Hu, Zunfeng Du, T. Sun, Zongqing Ma
ABSTRACT In order to prepare high-performance tungsten alloys, surface modification of tungsten nanopowders prepared by a wet chemical method was carried out by acid pickling at room temperature. The low-temperature sintering characteristics of tungsten nanpowders before and after pickling was compared and analysed. The surface modification was carried out by pickling with a solution of hydrofluoric acid, concentrated nitric acid and ammonium fluoride at room temperature. After this surface treatment, uniformly distributed step-shaped defects formed on the surface of the tungsten nanopowders. After low-temperature sintering, the grain size of the tungsten alloy corresponding to the surface-modified powder precursor was reduced by 20% compared to the alloy using untreated powder as precursor. In addition, the step-shaped defects also increase the sintering activity of the pickled tungsten powder and promote its sintering densification, making the final density of pure tungsten sintered at 1600°C as high as 96.7%, and its hardness greatly increased to 521 HV0.2. The results show that room-temperature pickling and subsequent low-temperature sintering is a promising method for preparing high-performance nanotungsten alloys.
{"title":"Effect of surface modification on the microstructure and sintering characteristics of tungsten nanopowders prepared by a wet chemical method","authors":"Xiangwei Kong, Weiqiang Hu, Zunfeng Du, T. Sun, Zongqing Ma","doi":"10.1080/09500839.2021.1910745","DOIUrl":"https://doi.org/10.1080/09500839.2021.1910745","url":null,"abstract":"ABSTRACT In order to prepare high-performance tungsten alloys, surface modification of tungsten nanopowders prepared by a wet chemical method was carried out by acid pickling at room temperature. The low-temperature sintering characteristics of tungsten nanpowders before and after pickling was compared and analysed. The surface modification was carried out by pickling with a solution of hydrofluoric acid, concentrated nitric acid and ammonium fluoride at room temperature. After this surface treatment, uniformly distributed step-shaped defects formed on the surface of the tungsten nanopowders. After low-temperature sintering, the grain size of the tungsten alloy corresponding to the surface-modified powder precursor was reduced by 20% compared to the alloy using untreated powder as precursor. In addition, the step-shaped defects also increase the sintering activity of the pickled tungsten powder and promote its sintering densification, making the final density of pure tungsten sintered at 1600°C as high as 96.7%, and its hardness greatly increased to 521 HV0.2. The results show that room-temperature pickling and subsequent low-temperature sintering is a promising method for preparing high-performance nanotungsten alloys.","PeriodicalId":19860,"journal":{"name":"Philosophical Magazine Letters","volume":"101 1","pages":"253 - 263"},"PeriodicalIF":1.2,"publicationDate":"2021-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/09500839.2021.1910745","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43755284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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