| 1. |
- Gyhlesten Back, Jessica, et al.
(författare)
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Microstructure analysis of martensitic low alloy carbon steel samples subjected to deformation dilatometry
- 2019
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Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- Low alloy martensitic steels are commonly used in structural and wear resistant applications due to their excellent mechanical properties and abrasion resistance. Martensite phase is generally achieved by rapid cooling, and prior deformation in the austenite region also affects the martensite transformation. It is important to understand the martensite transformation when there is deformation above Ae3. Deformation and quenching simulations have been performed using dilatometry on a low alloy carbon steel. The aim was to determine the influence of deformation above Ae3 (prior deformation) on, firstly, the austenite grain size and shape, and secondly, the martensitic microstructure and variant selection. In addition, the hardness of the martensitic structure due to prior deformation has been investigated. The experimental results obtained from electron backscatter diffraction and microhardness tests on the deformation dilatometry test samples were analysed. The orientation relationship Kurdjumov-Sachs has been used to analyse the martensitic variants. The results revealed a deeper understanding of prior austenite grain structure's effect on the martensitic transformation kinetics and its morphology. The martensite laths' misorientation interval 15–48° were used to visualise the prior austenite grain size. The martensitic lath structure is more refined due to increased prior deformation. Shorter martensite formation time promotes a single dominating packet within the prior austenite grain.
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| 2. |
- Habainy, J., et al.
(författare)
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Study of heavy ion beam induced damage in tungsten for high power target applications
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 439, s. 7-16
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Tidskriftsartikel (refereegranskat)abstract
- The spallation material at ESS is pure tungsten, which is cooled by gaseous helium flow. To study the behaviour of tungsten under dynamic beam conditions at ESS, pure tungsten specimens have been irradiated at the M3-beamline of the UNILAC facility at GSI Helmholtz Centre for Heavy Ion Research. Tungsten specimens of two thicknesses, 26 μm and 3 mm, were exposed to pulsed uranium and gold ion beams for fluences up to 7.5 · 1013 ions·cm−2 at 4.8 MeV/nucleon. Nanoindentation tests were performed on the cross section of the irradiated 3 mm sample, and microhardness was measured on the top surface. The measured data are compared with the calculated damage values, and a correlation between the radiation induced damage and the observed mechanical property is presented. Thermal diffusivities of foil samples irradiated up to four different fluences were measured with a Laser Flash Apparatus (LFA). The observed changes in the mechanical and thermal properties of irradiated tungsten were used to estimate the changes of operational temperature and mechanical stresses in the ESS target material with the progress of radiation damage, using coupled thermal and mechanical simulations. From the pulsed beam induced dynamic oscillations of thin tungsten specimens, information on fatigue properties of tungsten under irradiation was drawn. In addition to pure tungsten, oxidised tungsten samples were irradiated. This is to investigate the stability of the adhesive oxide layer under pulsed beam conditions, which would be formed due to oxygen impurities in the helium cooling loop. The irradiated oxide scale was examined using Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM).
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| 5. |
- Nath, Deo, et al.
(författare)
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Structure and properties of Al–Ni PM composites
- 2004
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Ingår i: Powder Metallurgy. - : Taylor & Francis. - 0032-5899 .- 1743-2901. ; 47:3, s. 247-252
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Tidskriftsartikel (refereegranskat)abstract
- Al–Ni powder mixtures containing 2, 4, 6 and 8 wt-% nickel were compacted at 125, 250, 375 and 500 MPa and sintered at 620, 630 and 640°C in a nitrogen atmosphere. The sintered density, sintered hardness and strength of composites thus produced were determined as a function of compaction pressure and sintering temperature. Wear rates of the composites were evaluated as a function of applied load and sliding velocity. Optical and scanning electron microscopy were used to reveal the morphology of powder and microstructures of green and sintered compacts. X-ray diffraction studies of the sintered compacts were made to confirm the phases formed on sintering. Sintered density, sintered hardness and strength increased with an increase in compaction pressure and nickel content. X-ray diffraction indicated the presence of Al3Ni phase in the sintered alloy. The wear rate of the sintered Al–Ni PM composite was found to increase with increasing load and decrease with increasing nickel content.
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| 7. |
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| 8. |
- Prashanth, Konda Gokuldoss, et al.
(författare)
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Powder metallurgy of high-strength Al90.4Y4.4Ni4.3Co0.9 gas-atomized powder
- 2012
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Ingår i: 13th International Conference on Aluminum Alloys (ICAA13). - Cham : Springer, Cham. ; , s. 1017-1022
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Konferensbidrag (refereegranskat)abstract
- Al90.4Y4.4Ni4.3Co0.9 gas-atomized powder was hot pressed (HP) to produce highly dense bulk samples through combined devitrification and consolidation. The microstructure of the as-atomized powder is a mixture of amorphous phase with nanocrystalline fcc Al, whereas the consolidated samples consists of fcc Al and a series of intermetallic phases with or without residual amorphous phase depending on the hot pressing temperature (673 or 723 K). The HP samples exhibit a remarkable high strength of ~ 925 MPa (HP at 673 K) and ~ 820 MPa (HP at 723 K) combined with a plastic strain ranging between 14 and 30%. The reduction in strength for the sample HP at 723 K is linked to the complete crystallization of the powder with no residual amorphous phase.
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