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- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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- Ahmadkhaniha, Donya, et al.
(författare)
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Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg
- 2017
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Konferensbidrag (refereegranskat)abstract
- High-pressure torsion (HPT) processing was applied to cast pure Mg pieces and its effects on microstructure, hardness and tensile properties as well as corrosion resistance were evaluated. The microstructure of the processed samples was examined by electron backscatter diffraction (EBSD) and the mechanical properties were determined by microhardness and tensile tests. Corrosion resistance of the samples was studied via electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The results showed that HPT refined the grain size of Mg very effectively from millimeters in the cast structure to a few micrometers homogeneously through the thickness and created a basal texture on the surface. One or five turns of HPT produced no significant difference in the grain size of the processed Mg but the hardness was a maximum after one turn. The yield strength of the cast Mg was increased by seven times whereas the corrosion resistance was not affected by the HPT processing.
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- Bibimoune, I., et al.
(författare)
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Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by high-pressure torsion using positron annihilation spectroscopy and a high resolution X-ray diffraction
- 2023
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Ingår i: Physica B: Condensed Matter. - 0921-4526. ; 663
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Tidskriftsartikel (refereegranskat)abstract
- Two MgRE (RE = Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DB-VEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ∼115 nm for the as-received state to ∼207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations (positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4–6 × 1014 m−2).
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- Langdon, P. G., et al.
(författare)
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A chironomid-based reconstruction of summer temperatures in NW Iceland since AD 1650
- 2011
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Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 75:3, s. 451-460
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Tidskriftsartikel (refereegranskat)abstract
- Few studies currently exist that aim to validate a proxy chironomid-temperature reconstruction with instrumental temperature measurements. We used a reconstruction from a chironomid percentage abundance data set to produce quantitative summer temperature estimates since AD 1650 for NW Iceland through a transfer function approach, and validated the record against instrumental temperature measurements from Stykkisholmur in western Iceland. The core was dated through Pb-210, Cs-137 and tephra analyses (Hekla 1693) which produced a well-constrained dating model across the whole study period. Little catchment disturbance, as shown through geochemical (Itrax) and loss-on-ignition data, throughout the period further reinforce the premise that the chironomids were responding to temperature and not other catchment or within-lake variables. Particularly cold phases were identified between AD 1683-1710. AD 1765-1780 and AD 1890-1917, with relative drops in summer temperatures in the order of 1.5-2 degrees C. The timing of these cold phases agree well with other evidence of cooler temperatures, notably increased extent of Little Ice Age (LIA) glaciers. Our evidence suggests that the magnitude of summer temperature cooling (1.5-2 degrees C) was enough to force LIA Icelandic glaciers into their maximum Holocene extent, which is in accordance with previous modelling experiments for an Icelandic ice cap (Langjokull). (C) 2010 University of Washington.
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