| 1. |
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| 2. |
- Divakar, M., et al.
(författare)
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Thermodynamics of surfaces and adsorption in the Fe-C-S-O system
- 2000
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940 .- 1073-5615 .- 1543-1916. ; 31:2, s. 267-276
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Tidskriftsartikel (refereegranskat)abstract
- Surface tension experiments have been conducted on Fe-C-S-O alloys using the sessile drop technique at 1823, 1873, and 1923 K in a purified argon atmosphere. The experimental data indicate lowering of surface tension values for alloys with low carbon and oxygen contents relative to the corresponding ternary Fe-S-O system of comparable compositions. The data exhibit an increasing trend of the surface tension values as a function of carbon and oxygen contents and temperature of the melt, Modified Butler's equations have been used in conjunction with the consistent thermodynamic relations for a dilute quaternary system to calculate the surface tensions and adsorption functions of the system, The calculated values are in excellent agreement with those of the experimental data for compositions having lower oxygen at 1823 K, however, the values for the alloys containing higher oxygen contents depart from those of the experimental data. The calculated surface tension values agree within 150 mN/m with those of the experimental data at 1873 K. The agreement, in general, has been favorable despite the constraints involved in the calculations as discussed in the text.
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| 3. |
- Seetharaman, Seshadri, et al.
(författare)
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Estimation of viscosities of ternary silicate melts using the excess Gibbs energy of mixing
- 2000
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940 .- 1073-5615 .- 1543-1916. ; 31:1, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- A correlation to predict the viscosities of ternary Silicates using the Gibbs energies of mixing of the silicate melts has been developed. This correlation has been employed to predict the viscosities of liquid slags in the systems FeO-MnO-SiO2, FeO-MgO-SiO2, CaO-FeO-SiO2, CaO-MnO-SiO2, and CaO-MgO-SiO2. The good agreement between the calculated viscosities and the experimental data in the ternary silicate systems has indicated that this approach can be successfully employed to predict the viscosities of ternary silicate melts.
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| 4. |
- Ahlström, Johan, 1969, et al.
(författare)
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Modified Railway Wheel Steels: Production and Evaluation of Mechanical Properties with Emphasis on Low-Cycle Fatigue Behavior
- 2009
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 40A:7, s. 1557-1567
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Tidskriftsartikel (refereegranskat)abstract
- Railway wheels are exposed to high mechanical and thermal loads. The objective of this study has been to develop wheels that are more resistant to damage from these loads. Fourteen different materials have been produced in the form of full-scale railway wheels. Parameters that have been varied include the chemical composition, production processes, and heat treatment. The materials have been investigated microstructurally and by hardness, tensile, and impact toughness testing. In addition, the low-cycle fatigue (LCF) behavior has been characterized at room temperature and at subzero temperatures. The results indicate improvement in microstructure and mechanical properties for some materials and it is probable that these materials would endure better in service. © The Minerals, Metals & Materials Society and ASM International 2009.
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| 5. |
- Alshahrani, M. A.M., et al.
(författare)
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High-Temperature Hydrogen Attack on 2.25Cr-1Mo Steel: The Roles of Residual Carbon, Initial Microstructure and Carbide Stability
- 2022
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 54, s. 3682-
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Tidskriftsartikel (refereegranskat)abstract
- High temperature hydrogen attack is a damage mechanism that occurs in critical steel components in petrochemical plants and refineries when the hydrogen penetrates the steel and reacts with the carbides within to produce pores containing methane. With the motivation of understanding the role of carbide stability on the reaction with hydrogen, samples of a classic 214Cr-1Mo steel were subjected to a variety of heat treatments that generate a corresponding variety of precipitates, prior to exposure to high-pressure hydrogen in an autoclave. Using quantitative carbide, porosity and microstructural characterisation, it has been possible to demonstrate the roles of four variables: (a) the carbon residue present in the ferrite; (b) the non-equilibrium chemical composition of carbide; (c) the fraction of the carbide that is closest to the thermodynamic equilibrium state and (d) the initial microstructural state, i.e., whether it is martensitic or bainitic prior to heat treatment.
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| 6. |
- Altenkirch, J., et al.
(författare)
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Mechanical Tensioning of High-Strength Aluminum Alloy Friction Stir Welds
- 2008
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Ingår i: Symposium on Neutron and X-Ray Studies for Probing Materials Behavior held at the 137th TMS Annual Meeting and Exhibition. - : Springer Science and Business Media LLC. - 1073-5623. ; 39A, s. 3246-3259
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Konferensbidrag (refereegranskat)abstract
- The extent to which in-situ global mechanical tensioning (GMT) can be used to modify the residual stress state in friction stir (FS) welds is investigated in this article. Residual stress distributions have been determined by synchrotron X-ray and neutron diffraction for four sets of FS welds in high-strength AA7449-W51 and lithium containing AA2199-T8 aerospace aluminum alloys subjected to a systematic range of GMT levels. For the cases studied, the results indicate that the level of residual stresses present in the as-welded state is a function of the alloy. The rate of residual stress reduction brought about by GMT, however, is basically alloy independent; indeed, it is essentially linear with respect to the GMT load, so that the tensioning required to reduce the weld stresses to zero can be calculated directly from the stresses present in the untensioned case. For thin plates, proximity to the yield stress in the hot-softened zone means that a guideline rule is that 1 MPa of tensioning during welding reduces the tensile stress by approximately 1 MPa. The GMT was found to be less effective at greater depths in thick plates. Furthermore, a reduction in bending distortion and an increase in angular distortion was observed with increased GMT, while no effects on the weld microstructure and hardness were observed.
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| 7. |
- Apaydin, R. O., et al.
(författare)
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Single-Step Production of Nanostructured Copper-Nickel (CuNi) and Copper-Nickel-Indium (CuNiIn) Alloy Particles
- 2016
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 47A:7, s. 3744-3752
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured copper-nickel (CuNi) and copper-nickel-indium (CuNiIn) alloy particles were produced from aqueous solutions of copper, nickel nitrates and indium sulfate by hydrogen reduction-assisted ultrasonic spray pyrolysis. The effects of reduction temperatures, at 973 K, 1073 K, and 1173 K (700 A degrees C, 800 A degrees C, and 900 A degrees C), on the morphology and crystalline structure of the alloy particles were investigated under the conditions of 0.1 M total precursor concentration and 0.5 L/min H-2 volumetric flow rate. X-ray diffraction studies were performed to investigate the crystalline structure. Particle size and morphology were investigated by scanning electron microscope and energy-dispersive spectroscopy was applied to determine the chemical composition of the particles. Spherical nanocrystalline binary CuNi alloy particles were prepared in the particle size range from 74 to 455 nm, while ternary CuNiIn alloy particles were obtained in the particle size range from 80 to 570 nm at different precursor solution concentrations and reduction temperatures. Theoretical and experimental chemical compositions of all the particles are nearly the same. Results reveal that the precursor solution and reduction temperature strongly influence the particle size of the produced alloy particles.
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| 8. |
- Arai, Y., et al.
(författare)
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In-situ observed dynamics of peritectic solidification and delta/gamma transformation of Fe-3 to 5 At. Pct Ni alloys
- 2005
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 36A:11, s. 3065-3074
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of liquid -> delta ferrite and delta ferrite -> gamma austenite transformation in Fe-3.50 at. pct Ni alloy, and of the peritectic solidification of Fe-4.83 and 5.01 at. pct Ni alloys, have been dynamically observed in situ with a confocal scanning laser microscope (CSLM) combined with an infrared image furnace (IIF). The unique sequence, morphologies, and rates of these transformations have been determined at a temperature gradient of 4 K/mm and growth rates of 2 to 3 mu m/s, in unidirectional solidification experiments. These observations have been discussed in terms of the constitutional undercooling description of solidification theory.
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| 9. |
- Asala, G., et al.
(författare)
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Microstructural Analyses of ATI 718Plus® Produced by Wire-ARC Additive Manufacturing Process
- 2017
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 48A:9, s. 4211-4228
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Tidskriftsartikel (refereegranskat)abstract
- A detailed microstructural study of ATI 718Plus superalloy produced by the wire-arc additive manufacturing (WAAM) process was performed through the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron probe micro-analysis (EPMA), and electron backscatter diffraction (EBSD). Extensive formation of eutectic solidification microconstituents including Laves and MC-type carbide phases, induced by micro-segregation, are observed in the build of the alloy in the as-deposited condition. Notwithstanding the significant segregation of niobium (Nb), which has been reported to promote the formation of the delta-phase in ATI 718Plus, only eta-phase particles are observed in the deposit. Excessive precipitation of eta-phase particles is found to be linked to Laves phase particles that are partially dissolved in the deposit after post-deposition heat treatment (PDHT). The EBSD analysis shows a high textured build in the aOE (c) 100 > directions with only a few misoriented grains at the substrate-deposit boundary and the top of the deposit. Investigation on the hardness of the build of the alloy, in the as-deposited condition, showed a softened zone about 2 mm wide at the deposited metal heat affected zone (DMHAZ), which has not been previously reported and potentially damaging to the mechanical properties. An extensive analysis with the use of both microstructural characterization tools and theoretical calculations shows that the DMHAZ has the lowest volume fraction of strengthening precipitates (gamma’ and gamma aEuro(3)) in terms of their number density, which therefore induces the observed softness. Delayed re-precipitation kinetics and the extent of the precipitation of gamma’ and gamma aEuro(3) in the DMHAZ which is related to the diffusion of segregated solute elements from the interdendritic regions are attributed to this phenomenon. The microstructural analyses discussed in this work are vital to adequate understanding of properties of ATI 718Plus produced by the additive manufacturing process technique.
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| 10. |
- Attallah, Moataz M., et al.
(författare)
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Microstructural and Residual Stress Development due to Inertia Friction Welding in Ti-6246
- 2012
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Ingår i: Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 43A:9, s. 3149-3161
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Tidskriftsartikel (refereegranskat)abstract
- A thorough investigation has been performed to assess the microstructural properties, mechanical properties (hardness and elastic modulus), and residual stress development in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) inertia friction welds in the as-welded and postweld heat-treated conditions. It was evident that the thermomechanical deformation in the weld region occurred above the beta transus, forming dynamically recrystallized beta grains and precipitating acicular alpha within the beta grains, which resulted in a localized hardness increase. In the heat-affected zone, a ghost microstructure of the base metal formed because of the absence of sufficient time for diffusion, resulting in Mo segregation in the prior primary alpha plates. Energy-dispersive synchrotron X-ray diffraction and neutron diffraction were used to assess the residual stress development in the three principal directions. The variation in the unstrained lattice parameters across the weld regions was established by imposing a stress balance on the axial stress component in the radial direction. It was found that the maximum stresses occurred in the hoop direction, with significantly lower stresses present in the radial and axial directions. The maximum tensile hoop stresses were located at similar to 4 mm from the weld centerline and not at the dynamically recrystallized beta-rich weld zone. This was associated with the alpha -> beta phase transformation and the subsequent acicular alpha precipitation within the region surrounding the weld centerline.
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