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1.
  • Abdul Abas, Riad, et al. (författare)
  • Thermal Diffusivity Measurements of some Industrially Important Alloys by a Laser Flash Method
  • 2007
  • Ingår i: International journal of materials reseach. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 98:6, s. 535-540
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, thermal diffusivity measurements of three industrially significant alloys, viz. 90Ti.6Al.4V, stainless steel with 25Cr and 6Ni as well as plain carbon steel with 0.7 % carbon have been carried out as a function of temperature. The aim of this work is to study the effect of temperature and microstructure on the thermal diffusivities of these alloys. For the 90Ti.6Al.4V alloy, thermal diffusivity increases with temperature below 1225 K. Above this temperature, the values started decreasing probably due to the dissolution of Ti3Al intermediate phase in the matrix, which would result in an increase in the disorder of the structure. For 25Cr: 6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Above this, there is an increase in the thermal diffusivities with temperature during the heating cycle, which was reproducible during thermal cycling. On the other hand, the slope of the curve increases above 950 K. In the case of the 0.7 % carbon steel, the thermal diffusivity shows a decreasing trend with temperature below the Curie point for the alloy, where the alloy consists of bcc + fcc phases. Above this point, only the fcc phase is prevalent and the thermal diffusivity was found to increase with temperature. Heat transfer is carried out by lattice vibration (phonons) as well as electrons. The contribution of electrons varies depending upon the type of alloy. In this study, the highest electron contribution was found in 0.7 % carbon steel, while the lowest was in stainless steel. The thermal conductivity values of these alloys are in good agreement with the calculated values using the model proposed by Mills.
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2.
  • Ahmed, Hesham M., et al. (författare)
  • Isothermal dynamic thermal diffusivity studies of the reduction of NiO and NiWO(4) precursors by hydrogen
  • 2011
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 102:11, s. 1336-1344
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermal diffusivity measurements of uniaxially cold pressed NiO and NiWO(4) were carried out in a dynamic mode in order to monitor the kinetics of hydrogen reduction of the above-mentioned materials using a laser flash unit. The calculated activation energy was found to be higher than that for chemically-controlled reaction obtained earlier by thermogravimetry. The difference has been attributed to physical changes occurring along with the chemical reaction. The activation energy of sintering of the products was evaluated to be 33 and 36 kJ.mol(-1) for NiO and NiWO(4), respectively. Thermal conductivities were calculated taking into consideration the change in heat capacity considering the compositional and the structural changes with the progress of the reaction. The potentiality of the laser-flash method as a complementary technique to thermogravimetry in understanding the mechanism of gas solid reactions is discussed.
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3.
  • Allertz, Carl, et al. (författare)
  • Effect of carbon on the solubility of nitrogen in slag
  • 2015
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 106:8, s. 822-830
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of carbon on nitrogen solubility in slag was investigated for the ternary CaO-MgO-SiO2 and the quaternary Al2O3-CaO-MgO-SiO2 slag systems at 1 873 K under controlled oxygen and nitrogen potentials. Gas-slag equilibration experiments were conducted using molybdenum and graphite crucibles. In the absence of carbon, the nitrogen solubility was very low. The presence of carbon greatly increased the nitrogen solubility in slag. The total nitrogen content was found to increase with SiO2 and MgO concentration for the carbon saturated slags. Low levels of cyanide were found by wet chemistry with considerable uncertainty. The results analyzed by different methods ruled out cyanide formation being the main reason for the large increase in nitrogen solubility in the presence of pure carbon.
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4.
  • Brillo, Juergen, et al. (författare)
  • Density and excess volumes of liquid copper, cobalt, iron and their binary and ternary alloys
  • 2006
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1526-1532
  • Tidskriftsartikel (refereegranskat)abstract
    • The densities of liquid copper, cobalt, and iron, their binary and ternary alloys have been measured over a temperature range including the undercooled regime. A non-contact technique was used, consisting of electromagnetic levitation combined with optical dilatometry. For all samples, the density was a linear function of temperature. The concentration dependence was studied by means of the excess volume which was negligible for Co-Fe and positive for Cu-Fe, Cu-Co, and Cu-Co-Fe. The density of the ternary alloy could be predicted from the excess volumes of the binary phases without the need to introduce any ternary interactions.
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5.
  • Brillo, Juergen, et al. (författare)
  • Density and excess volumes of liquid copper, cobalt, iron and their binary and ternary alloys
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1526-1532
  • Tidskriftsartikel (refereegranskat)abstract
    • The densities of liquid copper, cobalt, and iron, their binary and ternary alloys have been measured over a temperature range including the undercooled regime. A non-contact technique was used, consisting of electromagnetic levitation combined with optical dilatometry. For all samples, the density was a linear function of temperature. The concentration dependence was studied by means of the excess volume which was negligible for Co- Fe and positive for Cu- Fe, Cu- Co, and Cu-Co - Fe. The density of the ternary alloy could be predicted from the excess volumes of the binary phases without the need to introduce any ternary interactions.
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6.
  • Brillo, Jürgen, et al. (författare)
  • Density and excess volumes of liquid copper, cobalt, iron and their binary and ternary alloysRead More: http://www.hanser-elibrary.com/doi/abs/10.3139/146.101415
  • 2006
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1526-1532
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The densities of liquid copper, cobalt, and iron, their binary and ternary alloys have been measured over a temperature range including the undercooled regime. A non-contact technique was used, consisting of electromagnetic levitation combined with optical dilatometry. For all samples, the density was a linear function of temperature. The concentration dependence was studied by means of the excess volume which was negligible for Co–Fe and positive for Cu–Fe, Cu–Co, and Cu–Co–Fe. The density of the ternary alloy could be predicted from the excess volumes of the binary phases without the need to introduce any ternary interactions.
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7.
  • Brillo, Juergen, et al. (författare)
  • Density and surface tension of liquid ternary Ni-Cu-Fe alloys
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 97:1, s. 28-34
  • Tidskriftsartikel (refereegranskat)abstract
    • Density and surface tension of liquid Ni -Cu -Fe alloys have been measured over a wide temperature range, including the undercooled regime. A non-contact technique was used, consisting of an electromagnetic levitator, an optical densitometer, and an oscillating drop tensiometer. At temperatures above and below the liquidus point, density and surface tension are linear functions of temperature. The concentration dependence of the density is significantly influenced by a third-order (ternary) parameter in the volume, while the surface tensions can be derived from the thermodynamic potentials (E)G of the binary phases alone.
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8.
  • Burton, B. P., et al. (författare)
  • Using Ab Initio Calculations in the Calphad Environment
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 92:6, s. 514-525
  • Tidskriftsartikel (refereegranskat)abstract
    • Methods for applying first principles (FP) calculations to CALPHAD modeling, are discussed, with emphasis on easily calculated quantities that can be used to estimate input parameters for CALPHAD optimizations. Estimations of vibrational entropies, and melting points, from chemical systematics of measured elastic constants, or via semiempirical methods based on FP calculations are reviewed. Some strategies for including higher-order (clusters larger than pairs) short range order correlations in CALPHAD calculations are considered.
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9.
  • da Silva, Melina, 1978, et al. (författare)
  • A comparison of thermal stability in nanocrystalline Ni- and Co-based materials
  • 2005
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 96:09, s. 1009-1014
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper the microstructural development upon annealing of nanocrystalline Ni- and Co-based electrodeposits is described. New investigations on Ni, Ni - Fe, and Co-P are compared with previous results on Ni, Co, and Ni -P in terms of microstructural changes and stabilizing mechanisms. The conclusions are: pure nanocrystalline Ni and Co are stabilized by impurities in the grain boundaries. In the case of Co, also an allotropic phase transformation influences the occurrence of abnormal grain growth. Alloying and/or adding solutes is found to increase thermal stability. While in Ni-20 at.% Fe the ordering transformation is expected to be the reason for stabilization, in strongly segregating systems (Ni -P and Co-P) the stabilizing effect is the decrease in grain boundary energy due to solute segregation. After precipitation, Zener pinning still hinders grain boundary migration, but not sufficient to stabilize the nanocrystalline structure.
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10.
  • Delandar, Arash Hosseinzadeh, et al. (författare)
  • Dislocation dynamics modeling of plastic deformation in single-crystal copper at high strain rates
  • 2016
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Carl Hanser Verlag GmbH. - 1862-5282 .- 2195-8556. ; 107:11, s. 988-995
  • Tidskriftsartikel (refereegranskat)abstract
    • Tensile deformation of single-crystal copper along [001] orientation is modeled. Single crystal is deformed at three sets of high strain rates, ranging from 10(3) to 10(5) s(-1), using the three-dimensional dislocation dynamics technique to simulate dislocation microstructure evolution and the resultant macroscopic response. Two initial dislocation configurations consisting of straight dislocations and Frank-Read sources are randomly distributed over the simulation volume with an edge length of 1 mu m. For both initial setups, the mechanical response of the single crystal to the external loading demonstrates a considerable effect of strain rate. In addition, strain rate influences dislocation density evolution and consequently development of the dislocation microstructure. At all applied strain rates for both initial dislocation setups, dislocations evolve into a heterogeneous microstructure and this heterogeneity increases with plastic strain and strain rate.
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11.
  • Farooq, Muhammad, 1973, et al. (författare)
  • EBSD and EDX analysis at the cladding-substrate interface of a laser clad railway wheel
  • 2006
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1512-1518
  • Tidskriftsartikel (refereegranskat)abstract
    • Electron backscatter diffraction and energy-dispersive X-ray spectrometry were used to investigate the intermixed interface produced during laser cladding of a Co - Cr -Mo alloy on a steel substrate. A multi-component system and rapid solidification conditions together lead to a complex microstructure at the interface. The solidification of the cladding starts with the formation of an interface layer, which is about 75 mu m in thickness and consists of randomly oriented equiaxed grains of Co-Cr -Fe solid solution and martensite. Orientation analysis of the grains in the interface layer revealed that some grains have a special orientation relationship with the former austenite grains in the heat affected zone but the cladding is not formed by epitaxial growth on the substrate. Intermixing of the materials at the interface is providing a strong bond between the substrate and the cladding. For a grain from the interface layer to emerge as columnar grain in the cladding, it was determined that its crystallographic direction is not supposed to deviate more than 25 degrees from the sample normal direction.
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12.
  • Farooq, Muhammad, 1973, et al. (författare)
  • Microstructural characterisation of a Co-Cr-Mo laser clad applied on railway wheels
  • 2006
  • Ingår i: International Journal of Materials Research. - 1862-5282. ; 97:6, s. 838-844
  • Tidskriftsartikel (refereegranskat)abstract
    • A Co - Cr -Mo laser cladding applied on railway wheels is characterised by a combination of EBSD and EDX. A complete pass of the cladding is investigated to achieve a better understanding of the microstructure evolution during laser cladding. A microstructure with columnar grains extending over the whole thickness of the cladding is observed. The grains have a -fibre texture with the fibre axis parallel to the normal of the substrate surface, and a substructure consisting of cells/dendrites. During the cladding process, two different kinds of precipitates form in the cell walls, which can be identified as M6C and a non-equilibrium phase. Furthermore, stacking faults are observed to occur in the cladding grains and are discussed with respect to the laser cladding process.
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13.
  • Fjellstedt, Jonas, et al. (författare)
  • Experimental and Theoretical Study of the Al-Rich Corner in the Ternary Al-Ti-B System and Reassessment of the Al-Rich Side of the Binary Al-B Phase Diagram
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter. - 1862-5282 .- 2195-8556. ; 92:6, s. 563-571
  • Tidskriftsartikel (refereegranskat)abstract
    • The phase relations on the B-rich side of stoichiometric TiB2 were experimentally studied. It was found that a peritectic four-phase reaction liquid + AlB12 double left right arrow AlB2 + TiB2 occurs at a temperature between 1073 and 1173 K. Part of the Al-rich corner of the Al -Ti-B phase diagram was calculated and isothermal sections at 973, 1073, 1173 and 1273 K are presented. The peritectic four-phase reaction was calculated to occur at 1150 K in agreement with the experimental results. The Al-rich part of the binary Al -B system was reassessed. A eutectic reaction liquid double left right arrow AlB2 + (Al) was confirmed to occur at 932.9 K and 0.055 at.% B and a peritectic reaction liquid +AlB12 double left right arrow AlB2 concluded to happen at 1150 K (slightly above the four-phase reaction) and 0.60 at.% B, which is at a lower temperature than previously reported.
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14.
  • Frisk, Karin, et al. (författare)
  • Effect of Cr and v on phase equilibria in Co-WC based hardmetals
  • 2008
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 99:3, s. 287-293
  • Tidskriftsartikel (refereegranskat)abstract
    • New measurements of the influence of Cr and V on the melting temperature of the binder phase in Co-based hardmetals are presented. It was shown that both Cr and V affect the melting temperature significantly. Cr decreases the melting temperature by over 100°C, and V by approximately 40°C. This is due to the high solubility of Cr and V in liquid Co, and this solubility was determined by experiments and calculations. The solubility of Cr in solid fccCo is also discussed, as well as the composition of the MC, M7C3 and the M6C carbides in alloys with Cr and V. The new experimental information is used to obtain a reliable thermodynamic description of the binder phase (Co-rich) in C-Co-Cr-W and C-Co-V-W alloys. Calculated equilibria are compared with experiments. © Carl Hanser Verlag GmbH & Co. KG.
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15.
  • Godard, Claudia, et al. (författare)
  • Electron backscatter diffraction-analysis of deformed micro-milled commercially pure-titanium specimens at different strain values
  • 2017
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 108:10, s. 798-807
  • Tidskriftsartikel (refereegranskat)abstract
    • The surface structuring process micro-milling introducessmall grooves, which act as geometrical notches and influencethe mechanical properties of the component, into thesurface. The mechanical behaviour depends on the relationof the notch size to the grain size. Micro-milling processeswere applied to improve the functional properties of componentsurfaces. They are used in mechanically loaded environmentsas well as in biotechnological applications.Therefore, commercially-pure-titanium is a favoured materialof investigation. To determine the effect of the notches,a detailed analysis of the deformation behaviour of thestructured material is indispensable. In the present work,structured specimens were tested under quasi-static loading.The testing was interrupted at different strain values.The micro-sections of the specimens were characterizedby means of electron backscatter diffraction analysis to obtaininformation about the first indication of plastic deformationand the development of the deformation features.The results show inhomogeneous deformation behaviourof the material. The deformation mechanisms, the developmentof small angle and high angle grain boundaries as wellas twinning are shown.
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16.
  • Haglund, Sven, et al. (författare)
  • Sintering of WC-Co Under Axial Load
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 89:5, s. 323-326
  • Tidskriftsartikel (refereegranskat)abstract
    • Solid state sintering of cemented carbides is studied experimentally by means of dilatometry. Both an ordinary dilatometer and a dilatometer where an axial load was applied on the specimen were used. It is concluded that increased axial load, due to its hydrostatic component, gives larger volumetric shrinkage and that the decrease in the shrinkage rate at isothermal treatment is a result of a rapidly increasing rigidity of the powder compact at isothermal temperatures.
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17.
  • Haglund, Sven, et al. (författare)
  • Solid State Sintering of Cemented Carbides - An Experimental Study
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 89:5, s. 316-322
  • Tidskriftsartikel (refereegranskat)abstract
    • Solid state sintering of cemented carbides is studied experimentally by means of dilatometry and SEM. Surface analysis of the powders is performed by means of ESCA, Auger and SIMS. It is concluded that for pure WC-Co mixtures the major part of densification occurs in the solid state and that high heating rates yield higher densification rates. 200 ppm of Ti, preferentially located at grain surfaces, yield a drastic decrease in sintering rate. Melting of the binder, i. e. transition to liquid phase sintering, only has a minor effect on densification rate.
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18.
  • Hallstedt, Bengt, et al. (författare)
  • Thermodynamic evaluation of the Al-Cr-C system
  • 2006
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:5, s. 539-542
  • Tidskriftsartikel (refereegranskat)abstract
    • The system Al-Cr-C contains one ternary phase, Cr2AlC. By combining a Calphad assessment with ab initio calculations and differential thermal analysis, the Gibbs energy of Cr2AlC could be determined and the complete phase diagram calculated. Cr2AIC melts incongruently at about 1773 K to form Cr7C3 (or Cr3C2) and Al4C3 in addition to liquid. According to the ab initio calculations the equilibrium composition of Cr2AIC is very nearly stoichiometric, but can dissolve some Al metastably by replacing Cr. The agreement between the thermodynamic calculation and the various sources of information is excellent.
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19.
  • Hayashi, Miyuki, et al. (författare)
  • Thermal diffusivities of uniaxially cold-pressed Fe2Mo powders
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 94:11, s. 1179-1184
  • Tidskriftsartikel (refereegranskat)abstract
    • Fe2Mo powders have been produced from Fe2MoO4 powders by gas - solid reduction using pure H-2 gas at 1023 and 1173 K. The thermal diffusivity of the cold-pressed Fe2Mo powders having a relative density between 0.52 and 0.72 has been measured at room temperature both in air and in vacuum using the laser-flash method. A correlation was observed between the thermal diffusivity and the relative density for the powders reduced at different temperatures, regardless of the difference in microstructure of the powders. In order to explain the porosity dependence of the effective thermal conductivity, a new simple method developed based on the Ohm's law models was used. The model successfully simulates the experimental data, and the thermal conductivity of bulk Fe2Mo was estimated as 10.8 W/mK.
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20.
  • Hillert, Mats (författare)
  • Solute drag illustrated graphically
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 96:2, s. 104-107
  • Tidskriftsartikel (refereegranskat)abstract
    • There are two approaches to the interaction between solute atoms and migrating interfaces. A comparison between the two is illustrated with molar Gibbs energy diagrams. It is demonstrated that the present treatments of solute drag are equivalent to the treatment based on dissipation of Gibbs energy for grain boundary migration but not for phase transformations. A new treatment of solute drag is equivalent to the dissipation approach for both cases. It predicts that the solute drag changes sign for phase transformations and acts as a driving force.
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21.
  • Hoseiny, Seyyed Mohammad Hamed, 1980, et al. (författare)
  • The influence of microstructure and mechanical properties on the machinability of martensitic and bainitic prehardened mould steels
  • 2013
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 104:8, s. 748-761
  • Tidskriftsartikel (refereegranskat)abstract
    • The machinability of two prehardened mould steels, one continuously-cooled and one quenched and tempered, is compared in terms of cutting temperature, cutting force and tool life. Both materials have a hardness of similar to 40 HRC which is a typical hardness for prehardened mould steels. The results of machinability tests are related to mechanical properties and microstructural features, and the material removal rate is estimated for the materials. The continuously-cooled steel with bainitic structure shows higher machinability and possesses superior impact toughness and ductility compared to the quenched and tempered steel with martensitic structure. These properties are very important for plastic mould steels. The continuously-cooled bainitic steel also has the advantage of not requiring any costly quenching and tempering processes in connection with its production.
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22.
  • Huang, W., et al. (författare)
  • Thermodynamic Assessment of the Nb-W-C System
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 88:1, s. 55-62
  • Tidskriftsartikel (refereegranskat)abstract
    • The phase equilibrium and thermodynamic information of the Nb-W-C system was reviewed and assessed by using thermodynamic models for the Gibbs energy of individual phases. The assessment was based on the recent evaluations of the W-C, Nb-W and Nb-C, which was revised in the present work taking ternary information into account. The model parameters were evaluated by fitting the selected experimental data by means of a computer program. A consistent set of parameters was obtained, which satisfactorily describes most of the experimental information.
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23.
  • Hutchinson, Bevis, et al. (författare)
  • Deformation modes and anisotropy in magnesium alloy AZ31
  • 2009
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 100:4, s. 556-563
  • Tidskriftsartikel (refereegranskat)abstract
    • A strongly textured sheet of magnesium alloy AZ31 has been subjected to tensile testing at temperatures between ambient and 300 °C. Structures have been examined by optical and transmission electron microscopy and also by atomic force microscopy to quantify surface displacements seen at grain boundaries. Plastic anisotropy varies strongly with test temperature as was observed previously by Agnew and Duygulu. The present findings do not support the view that crystallographic becomes a major contributor to deformation at higher temperatures. Rather, the material behaviour reflects an increasing contribution from grain boundary sliding despite the relatively high strain rate (10-3 s-1 ) used in the mechanical tests. © Carl Hanser Verlag GmbH & Co. KG.
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24.
  • Hörnqvist Colliander, Magnus, 1979, et al. (författare)
  • Development of the unloading stiffness during cyclic plastic deformation of a high-strength aluminium alloy in different tempers
  • 2007
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 98:11, s. 1115-1123
  • Tidskriftsartikel (refereegranskat)abstract
    • The development of stiffness during unloading from peak stress during cyclic plastic deformation (low cycle fatigue) was studied in a high-strength Al-5.4Zn-1.2Mg alloy, both in naturally aged and peak aged conditions. A phenomenological model based on a 2nd order stress–strain relationship was developed using data from detailed recordings of the stress-strain hysteresis loops. Three stages of the parameter values were identified: an initial transition part of the fatigue life time, a major stationary stage shifting over to the final stage where failure modes become prominent. The nonlinear stiffness was found to be asymmetric with respect to tension and compression. Further, the naturally aged material generally shows larger stiffness for both positive and negative stresses than does the peak aged material. Finally, the stiffness for the naturally aged condition exhibits larger scatter compared to the peak aged materials, interpreted as inferior averaging in the dislocation structures.
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25.
  • Hörnqvist Colliander, Magnus, 1979, et al. (författare)
  • Effect of heat treatment on the strain hardening behaviour of an Al-Zn-Mg alloy
  • 2009
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 100:11, s. 1574 - 1581
  • Tidskriftsartikel (refereegranskat)abstract
    • The strain hardening of the Al-5.2Zn-1.2Mg alloy AA7030 in different conditions has been investigated. The dislocation related strengthening was described by the Voce equation and the quantitative effects of different superposition laws have been studied. All tempers, except the over-aged, suffer from plastic instability before the geometric Considère condition is reached. This was attributed primarily to the occurrence of shear failure due to dynamic strain ageing effects. For plastic strain levels below approximately 8 %, preceding the plastic instability, the results show that the saturation stress in the under and peak-aged tempers is independent of heat treatment, whereas the kinetics of structure formation differs. Using a linear superposition law in the under and peak aged tempers has negligible effects, whereas the use of Pythagorean addition for the over-aged temper significantly decreases the goodness-of-fit, although not to unacceptable levels. Furthermore, the naturally aged temper shows strong influence of dynamic precipitation.
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26.
  • Jiang, Kaiyun, et al. (författare)
  • On the high temperature stability of gamma-Al2O3/Ti0.33Al0.67N coated WC-Co cutting inserts
  • 2012
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Carl Hanser Verlag GmbH. - 1862-5282 .- 2195-8556. ; 103:12, s. 1509-1516
  • Tidskriftsartikel (refereegranskat)abstract
    • The high temperature stability of gamma-Al2O3 films deposited using filtered cathodic arc and plasma assisted chemical vapor deposition on Ti0.33Al0.67N coated WC-Co cutting inserts is investigated. X-ray diffractometry reveals that filtered cathodic arc deposited films transform partially into the thermodynamically stable alpha-Al2O3 phase at a temperature of 1000 degrees C. The gamma to alpha-Al2O3 transformation for plasma assisted chemical vapor deposition grown films is observed at 900 degrees C. These results are in qualitative agreement with differential scanning calorimetry measurements. Transmission electron microscopy on filtered cathodic arc and plasma assisted chemical vapor deposition films annealed at 900 degrees C reveals the existence of hexagonal AlN in the Ti0.33Al0.67N interlayer, as well as Al depletion at the Al2O3/Ti0.33Al0.67N interface. After annealing the plasma assisted chemical vapor deposition sample at 900 degrees C, alpha-Al2O3 grains with a size of 100 nm are observed inside the gamma-Al2O3 matrix, while for filtered cathodic arc samples only the gamma-phase is identified. Transmission electron microscopy analysis on both filtered cathodic arc and plasma assisted chemical vapor deposition samples annealed at 1000 degrees C shows that the original Al2O3/Ti0.33Al0.67N/WC-Co layer architecture is no longer intact. The formation of TiO2 is detected along the growth direction of the Al2O3 films. The present study suggests that not only the morphology and the impurities incorporated into gamma-Al2O3 but also stability of the Ti0.33Al0.67N interlayer determine the high temperature stability of gamma-Al2O3/Ti0.33Al0.67N coated hard-metal.
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27.
  • Johnsson, Mats, et al. (författare)
  • Study of Al1–xTixB2 Particles Extracted from Al–Ti–B Alloys
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - 1862-5282 .- 2195-8556. ; 89:6, s. 394-398
  • Tidskriftsartikel (refereegranskat)abstract
    • Al1-xTixB2 particles extracted from Al-Ti-B alloys have been investigated by means of a transmission electron microscope equipped with an X-ray energy-dispersive spectroscopic analyser. The solid solubility Al1-xTixB2 was found to be unlimited (0 <= x <= 1). The composition of boride particles extracted from an Al-Ti-B alloy with a composition within the solid solubility range was widely spread, whereas it was close to TiB2 for Ti concentrations in excess of the TiB2 stoichiometry. The particle size varied from 0.02 to 2 mu m. The largest particles were almost pure TiB2 or AlB2, but the small ones were solid solutions of varying compositions. Those small particles tended to form relatively large agglomerates. Due to impurities in the master alloys, vanadium was present in some boride particles, implying that we actually have an Al1-x(Ti1-yVy)(x)B-2 solid solution (0 <= x + y <= 1). The y value was found to vary within the range 0 <= y <= 0.07. It was found that master alloys containing boride particles with a narrow size distribution and a composition close to TiB2 gives better grain refinement results than master alloys with wide distributions of particle size and composition.
  •  
28.
  • Kjellqvist, Lina, 1979-, et al. (författare)
  • Thermodynamic assessment of the Mn-Ni-O system
  • 2010
  • Ingår i: International Journal for Materials Research Zeitschrift für Metallkunde. - Munchen : Carl Hanser Verlag. - 1862-5282 .- 2195-8556. ; 101:10, s. 1222-1231
  • Tidskriftsartikel (refereegranskat)abstract
    • The C-Cr-Fe-Ni-O system has recently been studied with the intention to thermodynamically describe the influence of oxygen on high alloyed steels. In this study the ternary Mn-Ni-O system is assessed. The liquid phase is assessed using the ionic two-sublattice model. Good agreement between calculated and experimental values are achieved.
  •  
29.
  • Kusoffsky, Alexandra, et al. (författare)
  • A Simplified Short Range Order Model Suitable for Multicomponent Alloys
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 89:12, s. 836-839
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this work has been to develop a model for short range order within the compound energy formalism. The short range order contribution to the Gibbs energy is described as a number of internal variables, here called epsilon-variables. This work is restricted to ordered and disordered phases with fcc structures.
  •  
30.
  • Li, Fan, et al. (författare)
  • A kinetic study of nickel coating on boron nitride micro-particles
  • 2007
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 98:6, s. 526-534
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, the mechanism of nickel coating on BN particles by hydrazine reduction was studied. A nickel sulfate - ammonium sulfate - ammonia - hydrazine hydrate plating system was employed. It was found that Pd on the surface of BN particles acted as an active center for nickel deposition at the initial stage of the process. Thereafter, Ni itself would act as an active center to catch Ni from the solution through the reaction: Ni2+, + 2H(ad)(*) double right arrow Ni + 2H(+). The rate of the process was found to be controlled by the reaction at the interface under the present experimental conditions. A kinetic model was proposed on the basis of the experimental results. The model predictions were found to be in agreement with the experimental data.
  •  
31.
  • Li, Fan, et al. (författare)
  • Nickel coating on some organic and carbon fibres by chemical plating
  • 2008
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 99:1, s. 84-91
  • Tidskriftsartikel (refereegranskat)abstract
    • A new method was developed to produce nickel coated fibres, which could be used as a raw material for making lightweight electrodes in nickel based secondary batteries. Hydrazine was employed as the reducing agent, ammonia solution as a complexing agent, nickel sulphate as the source of nickel ions and ammonia-ammonium sulphate as the buffer system. While the experiments confirmed that the ammonia-ammonium sulphate system could be applied for plating nickel on viscose, polyester, polyamide and carbon fibres, viscose fibre was found to be the more suitable material. The suitable operating conditions were reported.
  •  
32.
  • Li, Fan, et al. (författare)
  • Thermodynamic consideration and experimental study on preparation of hollow nickel fibres
  • 2008
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 99:9, s. 1023-1031
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, heat-treated hollow nickel fibres were prepared by thermal decomposition from nickel viscose composite. The thermodynamic properties of viscose fibre, namely standard enthalpy of formation, heat capacity, absolute entropy, and standard Gibbs free energy of formation were estimated by bond enthalpy. Thermodynamic analysis showed that viscose fibres could decompose at any reachable temperature, when the kinetic conditions were favourable. The results of thermogravimetric analysis experiments indicated that viscose filling could be removed by heat treatment in air. The thermogravimetric analysis results along with X-ray diffraction, scanning electron microscopy and X-ray energy dispersive spectrum analysis showed that hollow nickel fibre could be prepared by direct thermal decomposition in air flow at low temperatures, e.g. 573 K. Decomposition of the viscose filling could also be carried out at higher temperatures. However, serious oxidation of nickel would also take place during the decomposition. To remove nickel oxide, reduction by hydrogen gas could be applied.
  •  
33.
  • Lindberg, Daniel, et al. (författare)
  • Thermodynamic modeling of the stability and melting properties of sodium borates relevant to black liquor combustion and gasification
  • 2007
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - Münich : Carl Hanser Verlag GmbH. - 1862-5282 .- 2195-8556. ; 98:10, s. 1012-1018
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of borates as an autocausticizing agent in kraft recovery boilers of pulp mills is an interesting concept for decreasing the lime consumption at pulp mills. The main autocausticizing reaction is between NaBO2 and Na2CO3 forming Na3BO3 and CO2 at high temperatures in a liquid phase in the recovery boiler. The thermodynamic and phase equilibrium data of the Na2CO3-NaBO2-Na3BO3 system were evaluated and optimized. The liquid phase was modeled with the modified quasichemical model. The thermodynamic database obtained can be used to calculate the phase equilibrium and thermodynamic properties of multicomponent sodium salt mixtures of importance for the borate autocausticizing concept. The thermodynamic database is a part of an extensive thermodynamic database for alkali salt mixtures of importance for black liquor combustion in the pulp and paper industry.
  •  
34.
  • Lindwall, Greta, 1981-, et al. (författare)
  • The effect of nitrogen on the coarsening rate of precipitate phases in iron-based alloys with chromium and vanadium: experimental and theoretical investigations
  • 2013
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Carl Hanser Verlag. - 1862-5282 .- 2195-8556. ; 105:5, s. 442-451
  • Tidskriftsartikel (refereegranskat)abstract
    • A comparison of the coarsening of nitrogen-rich vanadium precipitates and the coarsening ofcarbon-rich vanadium precipitates is presented. The precipitate phases are studied experimentally,via fabrication of model alloys, and theoretically, via simulations utilizing the DICTRA software.The experimental investigations indicate that the nitrogen-rich precipitates exhibit a slowercoarsening behaviour than the carbon-rich precipitates. Analysis using thermodynamic andkinetic modelling shows that this can be explained by the higher thermodynamic stability of thenitrogen-rich precipitate compared to the carbon-rich precipitate. The calculated coarsening ratesare compared with the measured rates, and found to be in satisfactory agreement using reasonablevalues for the interfacial energies. The investigations are motivated by the ne precipitate sizedistribution of nitrides and carbonitrides characteristic for high nitrogen alloyed tool steels producedby means of powder metallurgy.
  •  
35.
  • Lundstrom, Dennis, et al. (författare)
  • Anisotropy in Thermal Transport Properties of Cast γ-TiAl Alloys
  • 2022
  • Ingår i: International Journal of Materials Research. - 1862-5282. ; 92:11, s. 1203-1212
  • Tidskriftsartikel (refereegranskat)abstract
    • The thermal transport properties have been determined for titanium aluminide with nominal composition Ti-48Al-2W-0.5Si (at.%), cast to cylindrical bars with different gamma/(gamma + alpha(2)) microstructures. The amount of phases and the orientation of the lamellar plates vary from the core to the rim in each of the bars. Differences in the thermal conductivity of the two phases lead to anisotropy in the thermal transport properties, but with cylindrical symmetry in the bars. A newly developed, high-precision technique, the so-called transient plane source (TPS) technique, was used to resolve the anisotropy in a wide temperature range. Typically, the conductivity increases monotonously from about 12- 14 W/m center dot K at room temperature up to about 20-22 W/m center dot K at 700 degrees C for the different materials. The anisotropy in both conductivity and diffusivity is about 15% at all temperatures, but with fundamental differences between the different materials. The anisotropy of the transport properties is explained in terms of amounts of phases and directionality of the lamellar plates.
  •  
36.
  • Markstrom, Andreas, et al. (författare)
  • Experimental and thermodynamic evaluation of the Co-Cr-C system
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 97:9, s. 1243-1250
  • Tidskriftsartikel (refereegranskat)abstract
    • New experimental results on the liquid + graphite + M7C3 equilibrium are presented. The solubility of Co in the M7C3 carbide has been measured at 1523 and 1723 K. These measurements together with recently published measurements on the fcc + graphite + M7C3 equilibrium show that the solubility of Co in the M7C3 is much higher than predicted from thermodynamic calculations. A new thermodynamic description of the Co-Cr -C system is presented which accurately describes the solubility of Co in the M7C3 carbide in the temperature range 1373 - 1723 K.
  •  
37.
  • Markström, Andreas, et al. (författare)
  • Experimental and thermodynamic evaluation of the Co-Cr-C system
  • 2006
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:9, s. 1243-1250
  • Tidskriftsartikel (refereegranskat)abstract
    • New experimental results on the liquid + graphite + M7C3 equilibrium are presented. The solubility of Co in the M7C3 carbide has been measured at 1523 and 1723K. These measurements together with recently published measurements on the fcc + graphite + M7C3 equilibrium show that the solubility of Co in the M7C3 is much higher than predicted from thermodynamic calculations. A new thermodynamic description of the Co–Cr –C system is presented which accurately describes the solubility of Co in the M7C3 carbide in the temperature range 1373 – 1723K.
  •  
38.
  • Mayrhofer, P.H., et al. (författare)
  • Spinodal decomposition of cubic Ti1-xAlxN : Comparison between experiments and modeling
  • 2007
  • Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 98:11, s. 1054-1059
  • Tidskriftsartikel (refereegranskat)abstract
    • Annealing of cubic (c) Ti1-xAlxN, possessing NaCl structure, leads to decomposition into the stable constituents c-TiN and hexagonal (h) AlN (ZnS wurtzite structure) via the formation of metastable C-TiN rich and metastable c-AlN rich phases. In this paper, we describe the influence of sizes of the newly formed particles and strain energy due to their different lattice parameter and elastic constants with respect to the remaining matrix on decomposition processes and energetics. Good agreement between the enthalpy output obtained from differential scanning calorimetry and values derived from ab-initio and continuum mechanical based calculations for the decomposition and transformation processes occurring is obtained. Based on the comparison between experiments including X-ray diffraction and small-angle neutron scattering of annealed samples and modeling we can conclude that spinodal decomposition is present in c-Ti1-xAlxN coatings with x = 0.50 and 0.66, whereas the alloy with x = 0.25 is outside the spinodal. © carl hanser verlag gmbh & co. Kg.
  •  
39.
  • Moverare, Johan, 1973-, et al. (författare)
  • Anisotropic high cycle fatigue behaviour of duplex stainless steels : influence of microstresses
  • 2002
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 93:1, s. 7-11
  • Tidskriftsartikel (refereegranskat)abstract
    • The anisotropic high cycle fatigue behaviour has been investigated for a duplex stainless steel in as-received and prestrained condition. It was found that the anisotropy of the fatigue limit is different from the anisotropy of yield strength. The main reason for this is the influence of microstresses on fatigue crack initiation. Fatigue cracks are seen to nucleate preferably in the austenite phase, which has tensile microstresses. Prestraining alters the microstresses from being higher in the transverse direction to being higher in the rolling direction. At the same time, the fatigue limit is changed from being higher in the rolling direction to being higher in the transverse direction.
  •  
40.
  • Muhmood, Luckman, et al. (författare)
  • Studies of dynamic mass transfer at the slag-metal interface - Interfacial velocity measurements
  • 2012
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 103:7, s. 875-883
  • Tidskriftsartikel (refereegranskat)abstract
    • The dynamics of oxygen transport along the slag-metal interface of pure iron and alumina-saturated CaO-Al2O3-SiO2 slag was studied using high-temperature X-ray image analysis. The oscillations of the metal drop occurring due to the interfacial movement of oxygen atoms driven by Marangoni forces were studied in detail. The change in interfacial area during the oscillations was measured using a digitizing software and MATLAB. It was observed that the interfacial velocity as a function of oxygen exhibits insignificant variation with temperature. Further, the values obtained for the interfacial velocity using oxygen concentration difference at the interface were slightly lower in comparison to those using sulfur. The possible reason for this lower velocity could be that, although oxygen is a smaller atom compared to that of sulfur, the energy barrier at the free iron surface is higher for oxygen, thus hindering its motion along the interface.
  •  
41.
  • Nakano, Anna, et al. (författare)
  • Synthesis of nano-manganese ferrite by an oxalate method and characterization of its magnetic properties
  • 2015
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Carl Hanser Verlag GmbH. - 1862-5282 .- 2195-8556. ; 106:12, s. 1264-1268
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, nano-sized manganese ferrite (MnFe2O4) was synthesized through the decomposition of the mixed oxalates. The formation of the spinel manganese ferrite was confirmed by X-ray diffraction analysis. The morphology of the ferrite products was studied by scanning electron microscopy. The particle size, which was determined using the Scherrer formula, ranged from 25 to 30 nm. Magnetic properties of the manganese ferrite were analyzed using a vibrating sample magnetometry technique; a narrow hysteresis loop indicated the MnFe2O4 obtained was a soft ferromagnet. Magnetic properties of the manganese ferrite produced were in agreement with those reported in literature for MnFe2O4 nanoparticles prepared by conventional methods, including co-precipitation and mechanochemical processes. By plotting a series of literature data determined by different authors and techniques, a correlation between saturation magnetisation and particle size has been noted regardless of the synthesis methods. In general, the oxalate method seems to be able to produce nano-manganese ferrite in a shorter time (2-3 h) as compared to other conventional techniques reported in literature (up to 54 h).
  •  
42.
  • Norgren, Susanne, et al. (författare)
  • Heat Capacity of DyFe2
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 89:12, s. 811-813
  • Tidskriftsartikel (refereegranskat)abstract
    • Experimental information on the heat capacity of DyFe2 is analyzed in terms of a vibrational contribution represented by the Einstein model, a magnetic contribution represented by the Inden-Hillert-Jarl model as well as a second order contribution aT + bT(2), a and b being adjustable parameters. As a comparison the heat capacity was obtained by the Neumann-Kopp rule with a magnetic contribution added.
  •  
43.
  • Ohnuma, Ikuo, et al. (författare)
  • Interaction between Magnetic and Chemical Ordering Using the Compound Energy Model
  • 2021
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 89:12, s. 847-854
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of interaction between the magnetic and chemical ordering reactions on the phase equilibria between the bcc phases, A2, B2 and DO3 has been studied by using the four-sublattice Compound Energy Model (CEM) taking account of the magnetic contribution to the Gibbs energy. An interaction between the magnetic and chemical ordering arises when the Curie temperature is formulated as a function of the site fraction of elements on each sublattice. A positive interaction arises from the higher deviation of the Curie temperature of the ordered state from that of the disordered one and leads to a two-phase separation between the ferro- and paramagnetic B2 phases. A lower deviation causes a negative interaction which introduces a convexity in the Gibbs energy curve around the composition of the intersection point between the Curie temperature and the order-disorder transition temperature. As a result, two-phase separations between either para- or ferro-magnetic A2 phase and paramagnetic B2 phase are introduced.
  •  
44.
  • Okamoto, Riki, et al. (författare)
  • Assessment of niobium segregation energy in migrating ferrite/austenite phase interfaces
  • 2010
  • Ingår i: INT J MATER RES. - : Walter de Gruyter GmbH. - 1862-5282. ; 101:10, s. 1232-1240
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of physical parameters on the total dissipation of Gibbs energy inside migrating ferrite/austenite interfaces have been re-investigated using Odqvist's solute drag model. It is shown that the mobility of the ferrite/austenite phase interface and the diffusivity of niobium in the interface have a strong effect on the Gibbs energy dissipation. As the phase interface mobility was recently reassessed, it is clear that the Gibbs energy of niobium segregation and the diffusivity of niobium in the interface must also be reassessed. In this paper both parameters are reassessed in the Fe-C-Nb system using new physical parameters and experimental results from ultra-low carbon steels.
  •  
45.
  • Rachbauer, Richard, et al. (författare)
  • Electronic origin of structure and mechanical properties in Y and Nb alloyed Ti-Al-N thin films
  • 2011
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : Hanser. - 1862-5282 .- 2195-8556. ; 102:6, s. 735-742
  • Tidskriftsartikel (refereegranskat)abstract
    • Ti(1-x)A(x)N thin films are industrially well established protective coatings, whose beneficial mechanical properties are mainly based on the formation of a metastable microstructure and local composition during film synthesis. Alloying of a transition metal (TM) to Ti(1-x)Al(x)N is a promising approach to reach yet higher oxidation and corrosion resistance in high-temperature environments, while maintaining a high intrinsic hardness and elasticity, being essential for a good wear performance. In order to study the effect of alloying with Y and Nb on the structure and mechanical properties of the industrially preferred cubic (c) Ti(1-x)Al(x)N system, quaternary Ti(1-x-z)Al(x)Y(z)N and Ti(1-x)Al(x)Nb(z)N films were deposited by means of plasma-assisted reactive magnetron sputtering and investigated using X-ray diffraction, transmission electron microscopy and nanoindentation. It is shown that Y addition to c-Ti(0.42)Al(0.58)N changes its structure towards single phase wurtzite (w) Ti(0.36)Al(0.55)Y(0.09)N, with deteriorated mechanical properties. In contrast, by the addition of Nb the structure remains cubic up to the studied composition of c-Ti(0.35)Al(0.57)Nb(0.08)N and the film hardness increases from 30.1 to 39.5 GPa. Ab initio studies show that the effect of Y and Nb alloying on structure and mechanical properties of quaternary Ti(1-x-z)Al(x)TM(z)N is not only correlated with strain increase due to lattice mismatch, but rather the changed electronic configuration.
  •  
46.
  • Skrinjar, Olle, et al. (författare)
  • A micromechanical analysis of local contact at die compaction of powder materials
  • 2011
  • Ingår i: INTERNATIONAL JOURNAL OF MATERIALS RESEARCH. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 102:3, s. 317-322
  • Tidskriftsartikel (refereegranskat)abstract
    • The present investigation concerns a finite element study of the local contact behavior of spherical powders in unit cell arrangements. Numerical results related to die compaction of unit cells of regular body-centered cubic lattices have been compared to previous analytical and numerical findings describing especially local but also global contact at powder compaction. In particular, previously published results concerning self-similarity contact are of interest here. Results relevant for isostatic compaction are also presented for comparative reasons. The finite element calculations are continued up to full density of solid material in the unit cells. The powder assembly is assumed to be composed of monolithic powder material.
  •  
47.
  • Skrinjar, Olle, et al. (författare)
  • On the micromechanics of die compaction of composite powder materials
  • 2011
  • Ingår i: INTERNATIONAL JOURNAL OF MATERIALS RESEARCH. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 102:4, s. 406-412
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present investigation a finite element study is performed concerning the local contact behavior of spherical powders in unit cell arrangements of composite powder materials. In particular, die compaction of unit cells of regular body-centered cubic lattices have been studied and the numerical results are compared to previous analytical and numerical findings describing, in particular, local contact but also global behavior in composite powder compaction. The foundation for the analytical results rests on previously published results where approximate composite contact relations are derived from self-similarity considerations in a situation where the powder particles are of the same material. Results pertinent to isostatic compaction are also presented for comparative reasons. The finite element calculations are continued up to full density of solid material in the unit cells.
  •  
48.
  • Smuk, Olena, et al. (författare)
  • The effect of copper on secondary phase precipitation in duplex stainless steel - a thermodynamic calculations approach
  • 2022
  • Ingår i: International Journal of Materials Research - Zeitschrift für Metallkunde. - : WALTER DE GRUYTER GMBH. - 1862-5282 .- 2195-8556. ; 96:8, s. 918-923
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermodynamic calculations with Thermo-Calc software and the steel database TCFE3 was applied to investigate the precipitation behavior of industrial grades of duplex stainless steels with high copper content, 1.6 and 2.3 wt.%, Duplok 27 and DUP 27, respectively. Well-documented super duplex stainless grade SAF 2507 with copper content of 0.20 wt.% was used as the reference steel. The results of the calculations are compared with the experimental results obtained previously for these steels. It is shown that copper decreases the high-temperature limit of precipitation of sigma and chi phases and reduces the equilibrium amount of precipitated chi phase. Copper addition to a duplex stainless steel facilitates precipitation of chromium nitride phase and stabilizes it at elevated temperatures. The ferrite-austenite balance at high temperatures is also affected in these steels by the copper addition.
  •  
49.
  • Stekovic, Svjetlana, et al. (författare)
  • Low-Cycle Fatigue and Damage of an Uncoated and Coated Single Crystal Nickel-Bse Superalloy SCB
  • 2007
  • Ingår i: International Journal of Materials Research. - 1862-5282. ; 98:1, s. 26-32
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents low-cycle fatigue (LCF) behaviour and damage mechanisms of uncoated and coated specimens of a single crystal nickel-base superalloy SCB tested at 500°C and 900°C. Four coatings were deposited on the base material, an overlay coating AMDRY997, a platinum-modified aluminide diffusion coating RT22 and two innovative coatings called IC1 and IC3 with a NiWdiffusion barrier in the interface. AMDRY997 and RT22 were used as reference coatings. The LCF tests were performed at three strain amplitudes, 1.0, 1.2 and 1.4%, with R ¼ % 1, in laboratory air and without any dwell time. The LCF life of the specimens is determined by crack initiation and propagation. Crack data are presented for different classes of crack size in the form of crack density, that is, the number of cracks normalised to the investigated interface length. Micrographs of damage of the coatings are also shown. The effect of the coatings on the LCF life of the superalloy was dependent on the test temperature and deposited coating. At 500°C all coatings had a detrimental effect on the LCF life of the superalloy. At 900°C both AMDRY997 and IC1 prolonged the fatigue life of the superalloy by factors ranging between 1.5 and 4 while RT22 and IC3 shortened the life of the coating–substrate system. Specimens coated with RT22 exhibited generally more damage than other tested coatings at 9008 C. Most of the cracks observed initiated at the coating surface and a majority were arrested in the interdiffusion zone between the base material and the coating. No topologically close-packed phases were found. Delamination was only found in AMDRY997 at higher strains. Surface roughness or rumpling was found in the overlay coating AMDRY997 with some cracks initiating from the rumples. The failure morphology at 900°C reflected the role of oxidation in the fatigue life, the crack initiation and propagation of the coated specimens. The wake of the cracks grown into the substrate was severely oxidised leading to the loss of Al and Ti to the oxide and resulting in the formation of a ϒ’ depleted zone. The cracks grew more or less perpendicular to the load axis in a Stage II manner.  
  •  
50.
  • Sterneland, Therese (författare)
  • Thermodynamic investigation of Co-Cr alloys, III : Thermo-analytical measurements using DSC and DTA techniques
  • 2006
  • Ingår i: INTERNATIONAL JOURNAL OF MATERIALS RESEARCH. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1533-1538
  • Tidskriftsartikel (refereegranskat)abstract
    • Several Co-Cr alloys have been investigated by Differential Scanning Calorimetry (DSC) as well as by Differential Thermal Analysis (DTA) in the temperature range 2981823 K. The compositional range investigated was from 0 to 87 wt.% Cr with special attention given to alloys with low Cr contents, i.e. 0 to 10 wt.% Cr. From the DSC measurements molar heat capacity values, phase transformation temperatures, enthalpies of transformation and Curie transition temperatures were derived. From the DTA measurements, the melting temperatures and melting enthalpies were evaluated. The trends obtained were compared with the results for pure Co as well as the proposed phase diagram reported in literature.
  •  
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