The possibilities of determining creep parameters for a simple Norton law material are explored from indentation creep testing. Using creep finite element analysis the creep indentation test technique is analyzed in t...The possibilities of determining creep parameters for a simple Norton law material are explored from indentation creep testing. Using creep finite element analysis the creep indentation test technique is analyzed in terms of indentation rates at constant loads. Emphasis is placed on the relationships between the steady creep behavior of indentation systems and the creep property of the indented materials. The role of indenter geometry, size effects and macroscopic constraints is explicitly considered on indentation creep experiments. The influence of macroscopic constraints from the material systems becomes important when the size of the indenter is of the same order of magnitude as the size of the testing material. Two methods have been presented to assess the creep property of the indented material from the indentation experimental results on the single-phase-material and two-phase-material systems. The results contribute to a better mechanical understanding and extending the application of indentation creep testing.展开更多
Based on the electronic theory recently proposed by the author for metal-ceramic interactions, the physical origin of the ion beam enhanced adhesion of non-reactive metal / ceramic systems was outlined for the first t...Based on the electronic theory recently proposed by the author for metal-ceramic interactions, the physical origin of the ion beam enhanced adhesion of non-reactive metal / ceramic systems was outlined for the first time. It has been shown that the ion beam enhanced adhesion is attributed to the enhancement of the chemical bonding between metal and ceramic. The copper / sapphire system was chosen as a typical example for demon- strations.展开更多
On the basis of the experimental work of adhesion(W)data,the adhesion between transition metal car- bides and pure liquid metals which do not react with carbides is studied.In view of great scattering of the ex- perim...On the basis of the experimental work of adhesion(W)data,the adhesion between transition metal car- bides and pure liquid metals which do not react with carbides is studied.In view of great scattering of the ex- perimental values of W,a critical analysis of these results is performed.The selected W values for 9 copper/carbide systems and 6 metal/TiC systems are used to discuss the various suggestions concerning the mechanism of adhesion and to evidence the role of the valence electrons of the both carbide and metal on the interactions between metals and carbides.The interactions between a metal and a carbide are essentially metal- lic interactions,resulting from the overlapping of the valence electrons at the metal/carbide interface.展开更多
The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex s...The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex systems with the desired multifunctionality.Herein,we apply multi-edge X-ray absorption spectroscopy(extended X-ray absorption fine structure(EXAFS),Xray absorption near edge structure(XANES),and X-ray magnetic circular dichroism(XMCD))to probe the structural,electronic,and magnetic properties of all individual constituents in the single-phase face-centered cubic(fcc)-structured nanocrystalline thin film of Cr_(20)Mn_(26)Fe_(18)Co_(19)Ni_(17)(at.%)high-entropy alloy on the local scale.The local crystallographic ordering and componentdependent lattice displacements were explored within the reverse Monte Carlo approach applied to EXAFS spectra collected at the K absorption edges of several constituents at room temperature.A homogeneous short-range fcc atomic environment around the absorbers of each type with very similar statistically averaged interatomic distances(2.54-2.55Å)to their nearest-neighbors and enlarged structural relaxations of Cr atoms were revealed.XANES and XMCD spectra collected at the L2,3 absorption edges of all principal components at low temperature from the oxidized and in situ cleaned surfaces were used to probe the oxidation states,the changes in the electronic structure,and magnetic behavior of all constituents at the surface and in the sub-surface volume of the film.The spin and orbital magnetic moments of Fe,Co,and Ni components were quantitatively evaluated.The presence of magnetic phase transitions and the co-existence of different magnetic phases were uncovered by conventional magnetometry in a broad temperature range.展开更多
文摘The possibilities of determining creep parameters for a simple Norton law material are explored from indentation creep testing. Using creep finite element analysis the creep indentation test technique is analyzed in terms of indentation rates at constant loads. Emphasis is placed on the relationships between the steady creep behavior of indentation systems and the creep property of the indented materials. The role of indenter geometry, size effects and macroscopic constraints is explicitly considered on indentation creep experiments. The influence of macroscopic constraints from the material systems becomes important when the size of the indenter is of the same order of magnitude as the size of the testing material. Two methods have been presented to assess the creep property of the indented material from the indentation experimental results on the single-phase-material and two-phase-material systems. The results contribute to a better mechanical understanding and extending the application of indentation creep testing.
文摘Based on the electronic theory recently proposed by the author for metal-ceramic interactions, the physical origin of the ion beam enhanced adhesion of non-reactive metal / ceramic systems was outlined for the first time. It has been shown that the ion beam enhanced adhesion is attributed to the enhancement of the chemical bonding between metal and ceramic. The copper / sapphire system was chosen as a typical example for demon- strations.
文摘On the basis of the experimental work of adhesion(W)data,the adhesion between transition metal car- bides and pure liquid metals which do not react with carbides is studied.In view of great scattering of the ex- perimental values of W,a critical analysis of these results is performed.The selected W values for 9 copper/carbide systems and 6 metal/TiC systems are used to discuss the various suggestions concerning the mechanism of adhesion and to evidence the role of the valence electrons of the both carbide and metal on the interactions between metals and carbides.The interactions between a metal and a carbide are essentially metal- lic interactions,resulting from the overlapping of the valence electrons at the metal/carbide interface.
文摘The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex systems with the desired multifunctionality.Herein,we apply multi-edge X-ray absorption spectroscopy(extended X-ray absorption fine structure(EXAFS),Xray absorption near edge structure(XANES),and X-ray magnetic circular dichroism(XMCD))to probe the structural,electronic,and magnetic properties of all individual constituents in the single-phase face-centered cubic(fcc)-structured nanocrystalline thin film of Cr_(20)Mn_(26)Fe_(18)Co_(19)Ni_(17)(at.%)high-entropy alloy on the local scale.The local crystallographic ordering and componentdependent lattice displacements were explored within the reverse Monte Carlo approach applied to EXAFS spectra collected at the K absorption edges of several constituents at room temperature.A homogeneous short-range fcc atomic environment around the absorbers of each type with very similar statistically averaged interatomic distances(2.54-2.55Å)to their nearest-neighbors and enlarged structural relaxations of Cr atoms were revealed.XANES and XMCD spectra collected at the L2,3 absorption edges of all principal components at low temperature from the oxidized and in situ cleaned surfaces were used to probe the oxidation states,the changes in the electronic structure,and magnetic behavior of all constituents at the surface and in the sub-surface volume of the film.The spin and orbital magnetic moments of Fe,Co,and Ni components were quantitatively evaluated.The presence of magnetic phase transitions and the co-existence of different magnetic phases were uncovered by conventional magnetometry in a broad temperature range.
