Blar i NTNU Open på forfatter "Holmestad, Randi"
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Nano-scale characterisation of sheared β” precipitates in a deformed Al-Mg-Si alloy
Christiansen, Emil; Marioara, Calin Daniel; Holmedal, Bjørn; Hopperstad, Odd Sture; Holmestad, Randi (Journal article; Peer reviewed, 2019)This paper compares the nano-scale structure of β” precipitates in a peak-aged Al-Mg-Si alloy before and after deformation. Three complementary advanced transmission electron microscopy techniques are used to reveal the ... -
Nanocrystal segmentation in scanning precession electron diffraction data
Bergh, Tina; Johnstone, D.N.; Crout, P; Høgås, Simon; Midgley, Paul A.; Holmestad, Randi; Vullum, Per Erik; Van Helvoort, Antonius (Journal article; Peer reviewed, 2019)Scanning precession electron diffraction (SPED) enables the local crystallography of materials to be probed on the nanoscale by recording a two‐dimensional precession electron diffraction (PED) pattern at every probe ... -
Nanoscale Characterisation of Deformed Aluminium Alloys
Christiansen, Emil (Doctoral theses at NTNU;2019:252, Doctoral thesis, 2019)Summary: Nanoscale Characterisation of Deformed Aluminium Alloys Abstract Understanding deformation of structures made from aluminium alloys is important for a range of industries. Aluminium producers must know ... -
Nanostructural Analysis of Co-Re/γ-Al2O3 Fischer-Tropsch Catalyst by TEM and XRD
Dehghan-Niri, Roya; Tsakoumis, Nikolaos E.; Voronov, Alexey; Holmen, Anders; Holmestad, Randi; Vullum, Per Erik; Borg, Øyvind; Rytter, Erling; Rønning, Magnus; Walmsley, John (Journal article; Peer reviewed, 2022)A rhenium promoted Fischer-Tropsch (FT) cobalt catalyst supported on γ-Al2O3 has been investigated by Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD), before and after reduction. Electron diffraction, ... -
On intermetallic phases formed during interdiffusion between aluminium alloys and stainless steel
Bergh, Tina; Arbo, Siri Marthe; Hagen, Anette Brocks; Blindheim, Jørgen; Friis, Jesper; Khalid, Muhammad Zeeshan; Ringdalen, Inga Gudem; Holmestad, Randi; Westermann, Ida; Vullum, Per Erik (Peer reviewed; Journal article, 2022)One of the major challenges in welding of aluminium (Al) alloys and steels is the growth of brittle intermetallic phases, which depends on the thermomechanical processing history and the alloying elements. This work focuses ... -
On the Atomic Structure of the β′′ Precipitate by Density Functional Theory
Frafjord, Jonas; Ringdalen, Inga Gudem; Holmestad, Randi; Friis, Jesper (Peer reviewed; Journal article, 2023)The substitution of elements into the precipitate in the 6xxx-series of aluminium alloys is an interface sensitive problem. The strain caused by the misfit between the precipitate and the matrix interacts with the size ... -
On the microstructural origins of improvements in conductivity by heavy deformation and ageing of Al-Mg-Si alloy 6101
Sunde, Jonas Kristoffer; Marioara, Calin Daniel; Wenner, Sigurd; Holmestad, Randi (Peer reviewed; Journal article, 2021)This work has examined an Al-0.54Mg-0.38Si (at.%) conductor alloy (6101) subjected to two different thermomechanical processing routes. Conventional solution treatment, quenching, and artificial ageing (170 °C) was compared ... -
On the Use of a Cluster Identification Method and a Statistical Approach for Analyzing Atom Probe Tomography Data for GP Zones in Al–Zn–Mg(–Cu) Alloys
Shah, Sohail; Thronsen, Elisabeth; de gauser, Frederic; hatzoglou, constantinos; Marioara, Calin Daniel; Holmestad, Randi; Holmedal, Bjørn (Peer reviewed; Journal article, 2023)Early-stage clustering in two Al–Mg–Zn(–Cu) alloys has been investigated using atom probe tomography and transmission electron microscopy. Cluster identification by the isoposition method and a statistical approach based ... -
Optimising multi-frame ADF-STEM for high-precision atomic-resolution strain mapping
Jones, Lewys; Wenner, Sigurd; Nord, Magnus Kristofer; Ninive, Per Harald; Løvvik, Ole Martin; Holmestad, Randi; Nellist, P.D. (Journal article; Peer reviewed, 2017)Annular dark-field scanning transmission electron microscopy is a powerful tool to study crystal defects at the atomic scale but historically single slow-scanned frames have been plagued by low-frequency scanning-distortions ... -
Orientation relationship between b-Si3N4 and Si in multicrystalline silicon ingots for PV applications
Undheim, Espen; Vullum, Per Erik; Holmestad, Randi; Arnberg, Lars; Di Sabatino Lundberg, Marisa (Journal article; Peer reviewed, 2018)β-Si3N4 particles are thought to be nucleation sites for silicon in multicrystalline silicon (mc-Si) ingots for PV applications. The orientation relationship (OR) between Si and β-Si3N4 has been investigated by transmission ... -
Orientation relationships of phase transformation in α-Al12Mn3Si pseudomorphs after plate-like Al6Mn precipitate in an AA3004 Al-Mn based alloy
Nakayasua, Hiroki; Kobayashi, Equo; Sato, Tatsuo; Holmestad, Randi; Marthinsen, Knut (Journal article; Peer reviewed, 2017)The phase transformation in the plate-like precipitates of Al6Mn in an AA3004 Al-Mn based alloy, which was prepared by a chemical extraction technique, was investigated using transmission electron microscopy. The boiling-phenol ... -
Phase stabilization principle and precipitate-host lattice influences for Al-Mg-Si-Cu alloy precipitates
Ehlers, Flemming J H; Wenner, Sigurd; Andersen, Sigmund Jarle; Marioara, Calin Daniel; Lefebvre, Williams; Boothroyd, Chris; Holmestad, Randi (Journal article, 2014)In this work, we seek to elucidate a common stabilization principle for the metastable and equilibrium phases of the Al–Mg–Si–Cu alloy system, through combined experimental and theoretical studies. We examine the structurally ... -
Potential Oxide-Based Intermediate Band Materials: Fabrication and Photoemission Studies
Jorge, Marina Rodrigues (Doctoral theses at NTNU;2020:83, Doctoral thesis, 2020)Intermediate band solar cells (IBSCs) is a so-called third generation solar cell concept, and are based on a new type of semiconductor materials which have an intermediate band (IB) within the bandgap. This IB works as a ... -
Precipitate statistics in an Al-Mg-Si-Cu alloy from scanning precession electron diffraction data
Sunde, Jonas Kristoffer; Paulsen, Øyvind; Wenner, Sigurd; Holmestad, Randi (Journal article; Peer reviewed, 2017)The key microstructural feature providing strength to age-hardenable Al alloys is nanoscale precipitates. Alloy development requires a reliable statistical assessment of these precipitates, in order to link the microstructure ... -
Precipitate Structure Changes during Overaging in an Al-Mg-Si Alloy
Granholt, Jason Daniel David A. (Master thesis, 2012)Starting from a super saturated solid solution and two different conditions withβ′′ precipitates (T6) an Al-Mg-Si alloy was heat treated at 200◦C and investigated byhardness measurements. One of the T6 conditions was ... -
Precipitate/matrix incompatibilities related to the {111}Al Ω plates in an Al-Cu-Mg-Ag alloy
Gazizov, M.R.; Boev, A.O.; Marioara, Calin Daniel; Holmestad, Randi; Aksyonov, D.A.; Gazizova, M.Yu.; Kaibyshev, R.O. (Journal article; Peer reviewed, 2021)The atomic structure of Ω plates forming on {111}Al planes in an Al-Cu-Mg-Ag alloy has been investigated by Z-contrast atomic-resolution scanning transmission electron microscopy imaging and ab initio density functional ... -
Precipitates in aluminium alloys
Andersen, Sigmund Jarle; Marioara, Calin Daniel; Friis, Jesper; Wenner, Sigurd; Holmestad, Randi (Journal article; Peer reviewed, 2018)Precipitation strengthening is a highly complex phenomenon on the nanoscale, responsible for providing strength in Al-Cu, Al-Mg-Cu, Al-Mg-Zn and Al-Mg-Si alloys. Advances in methodology, especially high-angle annular ... -
Precipitation behavior in an Al-Cu-Mg-Si alloy during ageing
Gazizov, Marat; Marioara, Calin Daniel; Friis, Jesper; Wenner, Sigurd; Holmestad, Randi; Kaibyshev, Rustam (Peer reviewed; Journal article, 2019)The precipitation behavior and aging response of an Al-4.9Cu-0.74Mg-0.51Si-0.48Mn-0.1Cr-0.08Ti-0.02Fe (wt. %) alloy was examined in detail after aging at 170 °C with different dwell times up to 96 h. Deformation by ... -
Precipitation behavior in an Al-Cu-Mg-Si alloy during ageing
Gazizov, Marat; Marioara, Calin Daniel; Friis, Jesper; Wenner, Sigurd; Holmestad, Randi; Kaibyshev, Rustam (Peer reviewed; Journal article, 2019)The precipitation behavior and aging response of an Al-4.9Cu-0.74Mg-0.51Si-0.48Mn-0.1Cr-0.08Ti-0.02Fe (wt. %) alloy was examined in detail after aging at 170 °C with different dwell times up to 96 h. Deformation by ... -
Precipitation behavior of Al-Si-Cu-Mg(-Fe) alloys by a deformation-semisolid extrusion process
Kim, DaeHan; Kim, JaeHwang; Wenner, Sigurd; Thronsen, Elisabeth; Marioara, Calin Daniel; Holmestad, Randi; Kobayashi, Equo (Journal article; Peer reviewed, 2021)