| 1. |
- Peng, Ru, 1960-, et al.
(författare)
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Determination of Grain-Orientation-Dependent Stress in Coatings
- 2005
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - 1012-0386 .- 1662-9507. ; 105, s. 107-112
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative interpretations of the so-called non-linear lattice strain distributions observed in coatings and thin films are important not only for determining the macro- and micro-stress fields, but also for inferring the active mechanisms of grain interactions during various deposition processes. In this paper, we present a method, which determines simultaneously both the macro- and micro-stress fields in the coatings and thin films. This method is extended from the previous stress-orientation distribution function (SODF) analysis method, which has already been used for residual stress analysis in bulk materials subjected to rolling and fatigue deformation. The validity of analysis method is demonstrated through measurements of lattice strains by high-energy x-ray and analysis of grain-orientation-dependent stresses in a CrN coating
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| 2. |
- Baretzky, B., et al.
(författare)
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Structure of historical brass tongues and shallots from Baroque organs
- 2006
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Ingår i: Diffusion and Defect Data. Pt A Defect and Diffusion Forum. - Stafa : Trans Tech Publications Ltd.. - 1012-0386 .- 1662-9507. ; 249, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- The composition and microstructure of historic tongues and shallots from reed pipes of various Baroque organs has been studied. They contain Cu-Zn solid solution (α-brass with 23-29 wt. % Zn) and lead particles. Lead is mainly present as spherical bulk or lens-like grain boundary (GB) inclusions. However, in two samples Pb wets the brass GBs. In this case Pb forms the branched root-like structures. Grain size in brass scatters from 10 to 200 μm. Around 50% of all GBs in brass are Σ=3 twin GBs. The high-indexed coincidence site lattice facets were observed in twin GBs. The increase of number of various facets roughly correlates with decreasing grain size. It may indicate the variation in annealing temperature used by organbuilders in Baroque Era. The annealing temperature has been estimated using the faceting phase diagram for twin GBs in Cu.
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| 3. |
- Blumenau, AT, et al.
(författare)
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Dislocation structures in diamond : density-functional based modelling and high-resolution electron microscopy
- 2004
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Ingår i: Defect and Diffusion Forum. - Zürich : Trans Tech Publications. - 1012-0386 .- 1662-9507. ; 226-228, s. 11-30
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Tidskriftsartikel (refereegranskat)abstract
- The core structures of perfect 60 and edge dislocations in diamond are investigated atomistically in a density-functional based tight-binding approach, and their dissociation is discussed both in terms of structure and energy. Furthermore, high resolution electron microscopy is performed on dislocation cores in high-temperature, high-pressure annealed natural brown diamond, and HRTEM image simulation allows a comparison of theoretically predicted and experimentally observed structures.
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| 4. |
- Bobyr, Serhii, et al.
(författare)
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Statistical Model of Hydrogen Diffusion in BCC Metals
- 2023
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - : Trans Tech Publications, Ltd.. - 1012-0386 .- 1662-9507. ; 429, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work is developing of the statistical model of hydrogen diffusion in the crystal lattice of BCC metals with an estimate of the contribution of quantum effects and deviations from the Arrhenius equation. The values of the statistical model calculations of H diffusion coefficients in Fe, V, Nb and Ta are in good agreement with the experimental data. The statistical model can also explain deviations from the Arrhenius equation at temperatures 300-500 K in Fe and Nb. The downward deviation of the diffusion coefficient at 300K can be explained by the fact that the statistical model does not consider the tunneling effect at temperatures below 300K. It was suggested that thermally activated fast tunnelling transition of hydrogen atoms through the potential barrier at temperatures below 500 K provides an almost free movement of H atoms in the α-Fe and V. Using the statistical model allows for the prediction of the diffusion coefficient for H in BCC metals at intermediate temperatures.
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| 5. |
- Coutinho, J., et al.
(författare)
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Limits to n-type doping in Ge : formation of donor-vacancy complexes
- 2008
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - 1012-0386 .- 1662-9507. ; 273-276, s. 93-98
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Tidskriftsartikel (refereegranskat)abstract
- Vacancies and interstitials in semiconductors play a fundamental role in both high temperature diffusion and low temperature radiation and implantation damage. In Ge, a serious contender material for high-speed electronics applications, vacancies have historically been believed to dominate most diffusion related phenomena such as self-diffusivity or impurity migration. This is to be contrasted with silicon, where self-interstitials also play decisive roles, despite the similarities in the chemical nature of both materials. We report on density functional calculations of the formation and properties of vacancy-donor complexes in germanium. We predict that most vacancy-donor aggregates are deep acceptors, and together with their high solubilities, we conclude that they strongly contribute for inhibiting donor activation levels in germanium.
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| 6. |
- Epishin, Alexander, et al.
(författare)
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Interdiffusion in cmsx-4 related ni-base alloy system at a supersolvus temperature
- 2021
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Ingår i: Defect and Diffusion Forum. - 1012-0386 .- 1662-9507. ; 407, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Interdiffusion in Ni-base superalloy CMSX-4 and alloys related to CMSX-4 was investigated at the temperature 1288 °C, which is 8 °C above the y’-solvus temperature of this superalloy, 1280 °C. This temperature is of a special interest because it is a temperature of hot isostatic pressing applied to CMSX-4 and modeling of this process needs verified diffusion data for this specific temperature. Various diffusion couples were assembled from the investigated alloys, annealed at 1288 °C and studied by electron probe microanalysis. So far as the annealing temperature was higher than the y’-solvus temperature of CMSX-4 and other investigated alloys have no strengthening y’-phase, interdiffusion occurred in the fcc solid solutions of nickel. It was found that in the case when the y’-forming and y-stabilizing elements diffuse in the same direction (towards nickel) the diffusion rate accelerates, but when they diffuse in the opposite directions (counter diffusion) it slows down. Such an interdiffusion behavior is in agreement with the results predicted with diffusion simulation software Dictra.
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| 7. |
- Gomez-Gallegos, A. A., 1983-, et al.
(författare)
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Studies on titanium alloys for aerospace application
- 2018
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - : Trans Tech Publications. - 1012-0386 .- 1662-9507. ; 385, s. 419-423
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Tidskriftsartikel (refereegranskat)abstract
- Since the development of the Ti54M titanium alloy in 2003, its application within the aerospace sector has gradually increased due to the combination of properties such as improved forgeability and machinability, low flow stress at elevated temperatures, and superplastic characteristics. However, for the successful exploitation of Ti54M a comprehensive understanding of its mechanical characteristics, microstructure stability, and superplastic behaviour is required. The superplastic forming of titanium alloys is characterised by high deformation at slow strain rates and high temperatures which influence the material microstructure, and in turn, determine the forming parameters. These mechanisms make the prediction of the material behaviour very challenging, limiting its application within the aerospace industry. Even though Ti54M has been commercially available for over 10 years, further studies of its mechanical and superplastic properties are still required with the aim of assessing its applicability within the aerospace industry as a replacement for other commercial titanium alloys. Therefore, in this work a study of the mechanical and superplastic properties of Ti54M, in comparison with other commercial titanium alloys used in the aerospace industry - i.e. Ti-6AL-4V, and Ti-6-2-4-2 - is presented. The final objective of this study, carried out at the Advanced Forming Research Centre (AFRC, University of Strathclyde, UK), is to obtain material data to calibrate and validate a model capable of estimating the behaviour and grain size evolution of titanium alloys at superplastic conditions.
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| 8. |
- Markevich, VP, et al.
(författare)
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Stable hydrogen pair trapped at carbon impurities in silicon
- 2003
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Ingår i: Defect and Diffusion Forum. - 1012-0386 .- 1662-9507. ; 221-2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Local mode spectroscopy and ab initio modeling are used to investigate two trigonal defects found in carbon rich Si into which H had been in-diffused. Isotopic shifts with D and C-13 are reported along with the effect of uniaxial stress. Ab-initio modeling studies suggest that the two defects are two forms of the CH2* complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed experimentally. The defects are energetically favorable in comparison with separated C-s and H-2 in Si and may represent aggregation sites for hydrogen.
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| 9. |
- Matsushita, Taishi, et al.
(författare)
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Thermal diffusivity of TiAlNb and AlNi alloys - The European IMPRESS project
- 2008
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Ingår i: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum. - Stafa : Trans Tech Publications Ltd.. - 1012-0386 .- 1662-9507. ; 273-276, s. 375-380
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Tidskriftsartikel (refereegranskat)abstract
- The thermal diffusivities of some industrially important alloys have been measured as a part of the EU funded Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) project which is coordinated by the European Space Agency (ESA). The thermal diffusivities of the alloys were measured by the Laser flash method with a carefully designed gas cleaning system to remove traces of oxygen from the argon atmosphere. In the present work, the thermal diffusivity of TiAlNb (Ti46.1Al45.9Nb8 at %) and AlNi alloy (Al-Ni31.5 at %) alloys have been measured independently at Royal Institute of Technology, Sweden (KTH) and National Physical Laboratory, UK (NPL). The results from both laboratories were consistent, and have been compared with predictions of phase transformation temperatures calculated using Thermo Calc and MTDATA software. Generally the variation of thermal diffusivity appears to be related to the phase transformation. However, one anomaly observed in the present work on TiAlNb was a maximum thermal diffusivity value at about HOOK. No corresponding peak was found for the density, ρ, the specific heat capacity, Cp, or the electrical resistivity, 1/σ, which were also measured as part of the project. In view of the fact that the thermal diffusivity could be related to electrical conductivity by the Wiedemann-Franz law describing electronic contribution to heat conduction, the present results indicate a non-electron contribution. This aspect is being currently investigated further. The recommended thermal diffusivity value of TiAlNb and AlNi alloys were obtained as follows. TiAlNb alloy: a = 3.75+ 5.16 ·10-3T+1.89·10-6 T2-2. 69·10-9 T3 [10-6 m2 s -1] (293 K < T < 1573 K) AlNi alloy: a = 4.77+ 5.41·10-2T- 7.14·10-5T2 + 2.88·10-8T3 [10-6 m2/s] (373K <T<943K).
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| 10. |
- Muhmood, L., et al.
(författare)
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A new approach for the diffusion coefficient evaluation of sulfur in CaO-SiO2-Al2O3 slag
- 2011
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Ingår i: 6th International Conference on Diffusion in Solids and Liquids, DSL-2010. - 9783037851173 ; 312-315, s. 626-634
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Konferensbidrag (refereegranskat)abstract
- The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The P S2 and PO2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 slag at 1723 K was estimated as 4.14×10-6 cm2/sec.
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