永瀬 丈嗣

The microstructure of rapidly solidified melt-spun ribbons obtained from [(Co0.9Zr0.1)(1-x)Cu-x](98)B-2 alloys with a wide Co/Cu ratio was investigated focusing on the liquid-phase separation and the formation of an amorphous phase. It was confirmed that the liquid-phase separation and the formation of an amorphous phase occurred simultaneously in Co-rich Co-Cu-Zr-B alloys. Spherical and ellipsoidal fcc-Cu crystalline precipitates of various sizes dispersed in the Co-Zr-based amorphous phase were obtained in the [(Co0.9Zr0.1)(1-x)Cu-x](98)B-2 alloy. (C) 2015 Elsevier B.V. All rights reserved.

Single crystals of Al0.3CoCrFeNi high entropy alloy were prepared by the floating zone method and the deformation behavior was examined. Dynamic strain aging accompanied by a serrated flow was found to occur in the single crystals at 873 K and 1073 K. Al atoms in the alloy played an important role in the dynamic strain aging. Distinct planar slip on (1 1 1) plane was also observed in Al0.3CoCrFeNi single crystals. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The microstructure of Co-Cu-based (Co0.75Si0.10B0.15)(100-x)Cu-x alloys was investigated for a wide range of Co/Cu ratios, with a focus on liquid phase separation and amorphous phase formation. The simultaneous occurrence of liquid phase separation and amorphous phase formation was confirmed in rapidly solidified (Co0.75Si0.10B0.15)(100-x)Cu-x (x = 10-50) alloys. Nano-scale emulsion-like structures were found in the macroscopically phase-separated Co-rich region in the (Co0.75Si0.10B0.15)(100-x)Cu-x (x = 30, 50) alloys. The microstructure in the CoeCueSieB alloys strongly depended on the solidification process and the Co/Cu ratio. (C) 2015 Elsevier B.V. All rights reserved.

Single crystals of Al0.3CoCrFeNi high entropy alloy were prepared by the floating zone method and the deformation behavior was examined. Dynamic strain aging accompanied by a serrated flow was found to occur in the single crystals at 873 K and 1073 K. Al atoms in the alloy played an important role in the dynamic strain aging. Distinct planar slip on (1 1 1) plane was also observed in Al0.3CoCrFeNi single crystals. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Abstract The microstructure of Co-Cu-based (Co&lt inf&gt 0.75&lt /inf&gt Si&lt inf&gt 0.10&lt /inf&gt B&lt inf&gt 0.15&lt /inf&gt )&lt inf&gt 100-x&lt /inf&gt Cu&lt inf&gt x&lt /inf&gt alloys was investigated for a wide range of Co/Cu ratios, with a focus on liquid phase separation and amorphous phase formation. The simultaneous occurrence of liquid phase separation and amorphous phase formation was confirmed in rapidly solidified (Co&lt inf&gt 0.75&lt /inf&gt Si&lt inf&gt 0.10&lt /inf&gt B&lt inf&gt 0.15&lt /inf&gt )&lt inf&gt 100-x&lt /inf&gt Cu&lt inf&gt x&lt /inf&gt (x = 10-50) alloys. Nano-scale emulsion-like structures were found in the macroscopically phase-separated Co-rich region in the (Co&lt inf&gt 0.75&lt /inf&gt Si&lt inf&gt 0.10&lt /inf&gt B&lt inf&gt 0.15&lt /inf&gt )&lt inf&gt 100-x&lt /inf&gt Cu&lt inf&gt x&lt /inf&gt (xc = 30, 50) alloys. The microstructure in the Co-Cu-Si-B alloys strongly depended on the solidification process and the Co/Cu ratio.

Abstract The microstructure of rapidly solidified melt-spun ribbons obtained from [(Co&lt inf&gt 0.9&lt /inf&gt Zr&lt inf&gt 0.1&lt /inf&gt )&lt inf&gt 1-x&lt /inf&gt Cu&lt inf&gt x&lt /inf&gt ]&lt inf&gt 98&lt /inf&gt B&lt inf&gt 2&lt /inf&gt alloys with a wide Co/Cu ratio was investigated focusing on the liquid-phase separation and the formation of an amorphous phase. It was confirmed that the liquid-phase separation and the formation of an amorphous phase occurred simultaneously in Co-rich Co-Cu-Zr-B alloys. Spherical and ellipsoidal fcc-Cu crystalline precipitates of various sizes dispersed in the Co-Zr-based amorphous phase were obtained in the [(Co&lt inf&gt 0.9&lt /inf&gt Zr&lt inf&gt 0.1&lt /inf&gt )&lt inf&gt 1-x&lt /inf&gt Cu&lt inf&gt x&lt /inf&gt ]&lt inf&gt 98&lt /inf&gt B&lt inf&gt 2&lt /inf&gt alloy.

The microstructure of rapidly solidified melt-spun ribbons of (Fe0.75M0.10B0.15)(100-x)Cu-x (M = Si, Zr) alloys was investigated focusing on amorphous-phase formation and the solidification structure. In this study, Fe-Cu-Si-B and Fe-Cu-Zr-B alloys were designed to show amorphous-phase formation and liquid-phase separation simultaneously. Amorphous-phase formation was confirmed in both Fe-Cu-Si-B and Fe-Cu-Zr-B alloys. Minor exceptions in a combination map of mixing enthalpy and quaternary predicted phase diagram are acceptable range for designing a quaternary Fe-Cu-based alloy system that shows liquid-phase separation in Fe-based and Cu-based liquids and the formation of an Fe-based amorphous phase. (C) 2015 Elsevier Ltd. All rights reserved.

The microstructure of rapidly solidified melt-spun ribbons of (Fe0.75M0.10B0.15)(100-x)Cu-x (M = Si, Zr) alloys was investigated focusing on amorphous-phase formation and the solidification structure. In this study, Fe-Cu-Si-B and Fe-Cu-Zr-B alloys were designed to show amorphous-phase formation and liquid-phase separation simultaneously. Amorphous-phase formation was confirmed in both Fe-Cu-Si-B and Fe-Cu-Zr-B alloys. Minor exceptions in a combination map of mixing enthalpy and quaternary predicted phase diagram are acceptable range for designing a quaternary Fe-Cu-based alloy system that shows liquid-phase separation in Fe-based and Cu-based liquids and the formation of an Fe-based amorphous phase. (C) 2015 Elsevier Ltd. All rights reserved.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, alpha-Pt2Si, was successfully formed at the platinum/silicon oxide interface under 25-200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation. It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation. (C) 2015 AIP Publishing LLC.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, alpha-Pt2Si, was successfully formed at the platinum/silicon oxide interface under 25-200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation. It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation. (C) 2015 AIP Publishing LLC.

The synthesis of metal silicide at the metal/silicon oxide interface by electronic excitation was investigated using transmission electron microscopy. A platinum silicide, alpha-Pt2Si, was successfully formed at the platinum/silicon oxide interface under 25-200 keV electron irradiation. This is of interest since any platinum silicide was not formed at the platinum/silicon oxide interface by simple thermal annealing under no-electron-irradiation conditions. From the electron energy dependence of the cross section for the initiation of the silicide formation, it is clarified that the silicide formation under electron irradiation was not due to a knock-on atom-displacement process, but a process induced by electronic excitation. It is suggested that a mechanism related to the Knotek and Feibelman mechanism may play an important role in silicide formation within the solid. Similar silicide formation was also observed at the palladium/silicon oxide and nickel/silicon oxide interfaces, indicating a wide generality of the silicide formation by electronic excitation. (C) 2015 AIP Publishing LLC.

The structural changes induced in a CoCrCuFeNi multicomponent nano-crystalline high-entropy alloy (HEA) under fast electron irradiation were investigated by in-situ transmission electron microscopy (TEM) using a high voltage electron microscope (HVEM). A fine-grained face centered cubic (fcc) single phase was obtained in the sputtered specimens. The fcc solid solution showed high phase stability against irradiation over a wide temperature range from 298 to 773 K, and remained as the main constituent phase even when the samples were irradiated up to 40 displacement per atom (dpa). Moreover, the irradiation did not seem to induce grain coarsening. This is the first report on the irradiation damage in 5-component HEA under MeV electron irradiation. (C) 2014 Elsevier Ltd. All rights reserved.

The structural changes induced in a CoCrCuFeNi multicomponent nano-crystalline high-entropy alloy (HEA) under fast electron irradiation were investigated by in-situ transmission electron microscopy (TEM) using a high voltage electron microscope (HVEM). A fine-grained face centered cubic (fcc) single phase was obtained in the sputtered specimens. The fcc solid solution showed high phase stability against irradiation over a wide temperature range from 298 to 773 K, and remained as the main constituent phase even when the samples were irradiated up to 40 displacement per atom (dpa). Moreover, the irradiation did not seem to induce grain coarsening. This is the first report on the irradiation damage in 5-component HEA under MeV electron irradiation. (C) 2014 Elsevier Ltd. All rights reserved.

The structural changes induced in a CoCrCuFeNi multicomponent nano-crystalline high-entropy alloy (HEA) under fast electron irradiation were investigated by in-situ transmission electron microscopy (TEM) using a high voltage electron microscope (HVEM). A fine-grained face centered cubic (fcc) single phase was obtained in the sputtered specimens. The fcc solid solution showed high phase stability against irradiation over a wide temperature range from 298 to 773 K, and remained as the main constituent phase even when the samples were irradiated up to 40 displacement per atom (dpa). Moreover, the irradiation did not seem to induce grain coarsening. This is the first report on the irradiation damage in 5-component HEA under MeV electron irradiation. (C) 2014 Elsevier Ltd. All rights reserved.

The microstructure of nanoglobules with a core-shell structure embedded in an Fe-Zr-B-based amorphous phase by liquid phase separation was investigated in an Fe-Cu-Zr-B immiscible alloy. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM) studies of the melt-spun ribbon clarified that an fcc Cu nanocrystalline core was covered by a B-enriched Fe-based amorphous shell in the nanoglobules.

The microstructure of arc-melted ingots and rapidly solidified melt-spun ribbons of quaternary Fe-Cu-Nb-B immiscible alloys was investigated, with a focus on amorphous-phase formation and solidification structure. A continuous melt-spun ribbon with an Fe-Nb-B-based amorphous matrix and 10-100 nm diameter fcc-Cu crystalline globules was obtained for the (Fe0.75Nb0.10B0.15)80Cu20alloy.

The formation of an amorphous phase was identified in Fe-Ag-based quaternary immiscible alloys of (Fe-M-B)-Ag, where M = Si, Zr, Nb. A macroscopically phase-separated melt-spun ribbon formed in the (Fe-Si-B)-Ag alloy was found to be composed of an fcc-Ag crystalline phase and an Fe-Si-B-based amorphous phase, a microstructure that is significantly different from that formed in an (Fe-Si-B)-Cu alloy system. An emulsion-type structure cannot be seen in the (Fe-Si-B)-Ag alloy.

The microstructure of nanoglobules with a core-shell structure embedded in an Fe-Zr-B-based amorphous phase by liquid phase separation was investigated in an Fe-Cu-Zr-B immiscible alloy. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM) studies of the melt-spun ribbon clarified that an fcc Cu nanocrystalline core was covered by a B-enriched Fe-based amorphous shell in the nanoglobules.

The existence of Pt&lt inf&gt 7&lt /inf&gt Cu ordering phase (intermetallic compound) was investigated by ab initio calculations and high voltage electron microscopy (HVEM) focusing on irradiationinduced ordering. The Pt&lt inf&gt 7&lt /inf&gt Cu ordering phase (cF32, prototype Ca&lt inf&gt 7&lt /inf&gt Ge) was predicted at 0 K through density functional theory (DFT), and using cluster expansion (CE) method and grand canonical Monte Carlo (GCMC) simulation, the ordering temperature of fcc-based Pt&lt inf&gt 7&lt /inf&gt Cu ordering phase was estimated to be above room temperature. The formation of Pt&lt inf&gt 7&lt /inf&gt Cu ordering phase was confirmed by a short-time irradiation for 3.6×10&lt sup&gt 3&lt /sup&gt s at 600 K. MeV electron irradiation can reduce drastically the annealing time for the ordering in the Pt-Cu alloy system, indicating that the combination of the prediction by ab initio calculations and HVEM can offer the unique opportunity to investigate the existence of ordering phase in alloys.

Si nanowire-based Tunnel-Field Effect Transistor (TFET) characteristics are intensively studied as function of nanowire diameter and doping. A significant reduction of B diffusion with decreasing nanowire diameter is e.g. observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In an Ultra High Voltage Electron Microscope (UHVEM), the formation of self-interstitial clusters can be studied in situ while varying e-beam flux, irradiation temperature, impurity concentration and capping layers surrounding the nanowires. Results are presented on {113}-defect formation in Si nanowires with diameters between 40 and 500 nm. The Si nanowires are embedded in SiO2 and are etched into an epitaxial Si stack on a heavily As doped Si substrate. The top layer of the epitaxial stack is in situ B doped or B implanted. In situ UHVEM studies are performed on focused ion beam prepared cross-section samples, irradiating with different fluxes of 2 MeV electrons between room temperature and 375 degrees C. A strong dependence of {113}-defect formation on nanowire radius and doping is observed. The observations are compared with simulations based on quasi-chemical reaction rate theory. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

When processing Si nanowire based Tunnel Field Effect Transistors (TFETS's), a significant reduction of B diffusion with decreasing nanowire diameter is observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In this study, Ultra High Voltage Electron Microscopy (UHVEM) is used to study in situ the formation of self-interstitial clusters in nanowire based TFET containing samples prepared by Focused Ion Beam (FIB) thinning. Si nanowires with diameters ranging from 40 to 500 nm are irradiated in an UHVEM using different fluxes of 2 MeV electrons at temperatures between room temperature and 375 degrees C. A strong dependence of defect formation on nanowire radius and on dopant concentration and type is observed. The UHVEM observations are compared with simulations based on quasi-chemical reaction rate theory and with two dimensional dopant concentration distributions determined with high-vacuum Scanning Spreading Resistance Microscopy (SSRM). (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The formation of an amorphous phase was identified in Fe-Ag-based quaternary immiscible alloys of (Fe-M-B)-Ag, where M = Si, Zr, Nb. A macroscopically phase-separated melt-spun ribbon formed in the (Fe-Si-B)-Ag alloy was found to be composed of an fcc-Ag crystalline phase and an Fe-Si-B-based amorphous phase, a microstructure that is significantly different from that formed in an (Fe-Si-B)-Cu alloy system. An emulsion-type structure cannot be seen in the (Fe-Si-B)-Ag alloy. (C) 2014 Elsevier B.V. All rights reserved.

When processing Si nanowire based Tunnel Field Effect Transistors (TFETS's), a significant reduction of B diffusion with decreasing nanowire diameter is observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In this study, Ultra High Voltage Electron Microscopy (UHVEM) is used to study in situ the formation of self-interstitial clusters in nanowire based TFET containing samples prepared by Focused Ion Beam (FIB) thinning. Si nanowires with diameters ranging from 40 to 500 nm are irradiated in an UHVEM using different fluxes of 2 MeV electrons at temperatures between room temperature and 375 degrees C. A strong dependence of defect formation on nanowire radius and on dopant concentration and type is observed. The UHVEM observations are compared with simulations based on quasi-chemical reaction rate theory and with two dimensional dopant concentration distributions determined with high-vacuum Scanning Spreading Resistance Microscopy (SSRM). (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Preparation of a sigma-CrFe single-phase specimen was achieved by arc melting of pure Fe and Cr, cold rolling, and subsequent annealing at 973 K or 1073 K in vacuum. Cold rolling before annealing is effective for the annealing-induced formation of sigma-CrFe from the bcc solid-solution phase. The phase stability and the structural change from sigma-CrFe to a bcc solid-solution phase under fast electron irradiation were investigated by in situ transmission electron microscope (TEM) observation in the temperature range between 22 K and 473 K by using an ultra-high voltage electron microscope (UHVEM). The phase transition of sigma-CrFe by fast electron irradiation was found to occur at a particular temperature.

Si nanowire-based Tunnel-Field Effect Transistor (TFET) characteristics are intensively studied as function of nanowire diameter and doping. A significant reduction of B diffusion with decreasing nanowire diameter is e.g. observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In an Ultra High Voltage Electron Microscope (UHVEM), the formation of self-interstitial clusters can be studied in situ while varying e-beam flux, irradiation temperature, impurity concentration and capping layers surrounding the nanowires. Results are presented on {113}-defect formation in Si nanowires with diameters between 40 and 500 nm. The Si nanowires are embedded in SiO2 and are etched into an epitaxial Si stack on a heavily As doped Si substrate. The top layer of the epitaxial stack is in situ B doped or B implanted. In situ UHVEM studies are performed on focused ion beam prepared cross-section samples, irradiating with different fluxes of 2 MeV electrons between room temperature and 375 degrees C. A strong dependence of {113}-defect formation on nanowire radius and doping is observed. The observations are compared with simulations based on quasi-chemical reaction rate theory. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The microstructure of arc-melted ingots and rapidly solidified melt-spun ribbons of quaternary Fe-Cu-Nb-B immiscible alloys was investigated, with a focus on amorphous-phase formation and solidification structure. A continuous melt-spun ribbon with an Fe-Nb-B-based amorphous matrix and 10-100 nm diameter fcc-Cu crystalline globules was obtained for the (Fe0.75Nb0.10B0.15)(80)Cu-20 alloy. (C) 2014 Elsevier B.V. All rights reserved.

The microstructure of nanoglobules with a core-shell structure embedded in an Fe-Zr-B-based amorphous phase by liquid phase separation was investigated in an Fe-Cu-Zr-B immiscible alloy. Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM) studies of the melt-spun ribbon clarified that an fcc Cu nanocrystalline core was covered by a B-enriched Fe-based amorphous shell in the nanoglobules. (C) 2014 Elsevier B.V. All rights reserved.

When processing Si nanowire based Tunnel Field Effect Transistors (TFETS's), a significant reduction of B diffusion with decreasing nanowire diameter is observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In this study, Ultra High Voltage Electron Microscopy (UHVEM) is used to study in situ the formation of self-interstitial clusters in nanowire based TFET containing samples prepared by Focused Ion Beam (FIB) thinning. Si nanowires with diameters ranging from 40 to 500 nm are irradiated in an UHVEM using different fluxes of 2 MeV electrons at temperatures between room temperature and 375 degrees C. A strong dependence of defect formation on nanowire radius and on dopant concentration and type is observed. The UHVEM observations are compared with simulations based on quasi-chemical reaction rate theory and with two dimensional dopant concentration distributions determined with high-vacuum Scanning Spreading Resistance Microscopy (SSRM). (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The microstructure of rapidly solidified melt-spun ribbons of (Fe0.75M0.10B0.15)100-xCux (M = Si, Zr) alloys was investigated focusing on amorphous-phase formation and the solidification structure. In this study, Fe-Cu-Si-B and Fe-Cu-Zr-B alloys were designed to show amorphous-phase formation and liquid-phase separation simultaneously. Amorphous-phase formation was confirmed in both Fe-Cu-Si-B and Fe-Cu-Zr-B alloys. Minor exceptions in a combination map of mixing enthalpy and quaternary predicted phase diagram are acceptable range for designing a quaternary Fe-Cu-based alloy system that shows liquid-phase separation in Fe-based and Cu-based liquids and the formation of an Fe-based amorphous phase.

Si nanowire-based Tunnel-Field Effect Transistor (TFET) characteristics are intensively studied as function of nanowire diameter and doping. A significant reduction of B diffusion with decreasing nanowire diameter is e.g. observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out-diffusion of excess self-interstitials. In an Ultra High Voltage Electron Microscope (UHVEM), the formation of self-interstitial clusters can be studied in situ while varying e-beam flux, irradiation temperature, impurity concentration and capping layers surrounding the nanowires. Results are presented on {113}-defect formation in Si nanowires with diameters between 40 and 500 nm. The Si nanowires are embedded in SiO2 and are etched into an epitaxial Si stack on a heavily As doped Si substrate. The top layer of the epitaxial stack is in situ B doped or B implanted. In situ UHVEM studies are performed on focused ion beam prepared cross-section samples, irradiating with different fluxes of 2 MeV electrons between room temperature and 375 degrees C. A strong dependence of {113}-defect formation on nanowire radius and doping is observed. The observations are compared with simulations based on quasi-chemical reaction rate theory. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The microstructure of arc-melted ingots and rapidly solidified melt-spun ribbons of quaternary Fe-Cu-Nb-B immiscible alloys was investigated, with a focus on amorphous-phase formation and solidification structure. A continuous melt-spun ribbon with an Fe-Nb-B-based amorphous matrix and 10-100 nm diameter fcc-Cu crystalline globules was obtained for the (Fe0.75Nb0.10B0.15)(80)Cu-20 alloy. (C) 2014 Elsevier B.V. All rights reserved.

Reduced activation ferritic/martensitic steels (RAFMs), such as F82H steel, are designed to enhance the high-temperature strength by formation of MX-type nanometer-scale precipitates, mainly TaC. However, their instability under irradiation was recently reported. The purpose of this work, therefore, is to clarify the mechanism employing simultaneous observations under electron irradiation at elevated temperature in a high voltage electron microscope. In this work, Fe-0.2 wt.% TaC was fabricated as a model alloy of F82H steel. The instability of the precipitates was observed under electron irradiation at 1 MeV or above. The remarkable shrinkage and disappearance were clearly observed under irradiation with 1.5 MeV and above. On the contrary, the precipitates were mostly stable below 0.75 MeV. Two kinds of mechanism of the irradiation-induced instability were deduced from the electron-energy dependence. One is the dissolution and diffusion of tantalum from precipitates in ferrite matrix. The other is the displacements of tantalum in precipitates that introduce dissolution of Ta into matrix. (C) 2014 Elsevier B.V. All rights reserved.