• A hybrid aluminium alloy and its zoo of interacting nano-precipitates 

      Wenner, Sigurd; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Ervik, Martin; Holmestad, Randi (Journal article, 2015)
      An alloy with aluminium as its base element is heat treated to form a multitude of precipitate phases known from different classes of industrial alloys: Al–Cu(–Mg), Al–Mg–Si–Cu, and Al–Zn–Mg. Nanometer-sized needle-shaped ...
    • A study of the influence of precipitate free zones on the strain localization and failure of the aluminium alloy AA7075-T651 

      Fourmeau, Marion; Marioara, Calin Daniel; Børvik, Tore; Benallal, Ahmed; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2015)
      Age-hardened aluminium alloys have various degrees of precipitate-free zones (PFZs) along grain boundaries (GBs). The PFZs are weak zones and their existence promotes combined transgranular and intergranular fracture, thus ...
    • Aberration-corrected HAADF-STEM investigations of precipitate structures in Al-Mg-Si alloys with low Cu additions 

      Saito, Takeshi; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Lefebvre, Williams; Holmestad, Randi (Journal article, 2014)
      Precipitates in a lean Al–Mg–Si alloy with low Cu addition (~0.10 wt.%) were investigated by aberration-corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Most precipitates were ...
    • An unreported precipitate orientation relationship in Al-Zn-Mg based alloys 

      Bendo, Artenis; Matsuda, Kenji; Lervik, Adrian; Tsuru, Tomohito; Nishimura, Katsuhiko; Nunomura, Norio; Holmestad, Randi; Marioara, Calin Daniel; Shimuzu, Kazuyuki; Toda, Hiroyuki; Yamaguchi, Masatake (Journal article; Peer reviewed, 2019)
      Characterization of precipitates in Al-Zn-Mg alloys, using a combination of electron diffraction, bright field transmission electron microscopy and atomic scale scanning transmission electron microscopy imaging revealed ...
    • Atomic structures of precipitates in Al–Mg–Si alloys with small additions of other elements 

      Saito, Takeshi; Mørtsell, Eva Anne; Wenner, Sigurd; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Friis, Jesper; Matsuda, Kenji; Holmestad, Randi (Journal article; Peer reviewed, 2018)
      In Al–Mg–Si alloys, additions of only a few weight percent of Mg and Si enable formation of hardening precipitates during heat treatment. The precipitation is complex and is influenced by chemical compositions and ...
    • Atomic-resolution chemical mapping of ordered precipitates in Al alloys using energy-dispersive X-ray spectroscopy 

      Wenner, Sigurd; Jones, Lewys; Marioara, Calin Daniel; Holmestad, Randi (Journal article, 2017)
      Scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDS) is a common technique for chemical mapping in thin samples. Obtaining high-resolution elemental maps in the STEM is ...
    • Atomic-resolution electron energy loss studies of precipitates in an Al-Mg-Si-Cu-Ag alloy 

      Wenner, Sigurd; Marioara, Calin Daniel; Ramasse, Quentin; Kepaptsoglou, Despoina Maria; Hage, Fredrik Sydow; Holmestad, Randi (Journal article, 2014)
      Aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy has been used to determine the distribution of Cu and Ag atomic columns of precipitates in an Al–Mg–Si–Cu–Ag ...
    • Atomic-resolution elemental mapping of precipitates in a 7449 aluminium alloy 

      Wenner, Sigurd; Marioara, Calin Daniel; Lefebvre, Williams; Ramasse, Quentin; Kepaptsoglou, Despoina Maria; Hage, Fredrik Sydow; Holmestad, Randi (Journal article, 2014)
      The high-strength weldable 7xxx series of aluminium alloys are of great importance to the aeronautics industry. Only recently, the complex structures of the AlZnMg hardening precipitates have been solved by HAADFSTEM imaging ...
    • Atomistic details of precipitates in lean Al–Mg–Si alloys with trace additions of Ag and Ge studied by HAADF-STEM and DFT 

      Mørtsell, Eva Anne; Andersen, Sigmund Jarle; Friis, Jesper; Marioara, Calin Daniel; Holmestad, Randi (Journal article, 2017)
      Bonding energies and volume misfits for alloying elements and vacancies in multicomponent Al–Mg–Si alloys have been calculated using density functional theory (DFT). A detailed atomic scale analysis has been done for ...
    • Carbon nanofibers have IgE adjuvant capacity but are less potent than nanotubes in promoting allergic airway responses 

      Nygaard, Unni Cecilie; Samuelsen, Mari; Marioara, Calin Daniel; Løvik, Martinus (Journal article; Peer reviewed, 2013)
      There is a growing concern for the possible health impact of nanoparticles. The main objective of this study was to investigate the allergy-promoting capacity of four different carbon nanofiber (CNF) samples in an injection ...
    • Characterisation of structural similarities of precipitates in Mg–Zn and Al–Zn–Mg alloys systems 

      Bendo, Artenis; Maeda, Tomoyoshi; Matsuda, Kenji; Lervik, Adrian; Holmestad, Randi; Marioara, Calin Daniel; Nishimura, Katsuhiko; Nunomura, Norio; Toda, Hiroyuki; Yamaguchi, Masatake; Ikeda, Ken-ichi; Homma, Tomoyuki (Journal article; Peer reviewed, 2019)
      High angle annular dark field scanning transmission electron microscopy has been employed to observe precipitate structures in Al–Zn–Mg and Mg–Zn alloys. h1 precipitate structures in Al–Zn–Mg are commonly formed by MgZn2 ...
    • Characterization and structure of precipitates in 6xxx Aluminium Alloys 

      Holmestad, Randi; Bjørge, Ruben; Ehlers, Flemming J H; Torsæter, Malin; Marioara, Calin Daniel; Andersen, Sigmund Jarle (Journal article; Peer reviewed, 2012)
      Solute atom nanoscale precipitates are responsible for the favourable mechanical properties of heat treatable aluminium alloys such as Al-Mg-Si (6xxx). The shape, structure and strengthening properties of age-hardening ...
    • Clustering and Vacancy Behavior in High- and Low-Solute Al-Mg-Si Alloys 

      Wenner, Sigurd; Nishimura, Katsuhiko; Matsuda, Kenji; Matsuzaki, Teiichiro; Tomono, Dai; Pratt, Francis L.; Marioara, Calin Daniel; Holmestad, Randi (Journal article, 2014)
      The precipitate microstructure and vacancy distribution in Al-Mg-Si alloys with different amounts of solute and different heat treatments were investigated by transmission electron microscopy and muon spin relaxation ...
    • Cu atoms suppress misfit dislocations at the β″/Al interface in Al-Mg-Si alloys 

      Saito, Takeshi; Ehlers, Flemming J H; Lefebvre, Williams; Hernandez-Maldonado, David; Bjørge, Ruben; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Mørtsell, Eva Anne; Holmestad, Randi (Journal article, 2016)
      The Cu interactions with the Al–Mg–Si alloy main hardening phase β″ are investigated in atomic scale, by using experimental and simulated high angle annular dark-field scanning transmission electron microscopy techniques ...
    • Deformation and strain localization in polycrystals with plastically heterogeneous grains 

      Khadyko, Mikhail; Marioara, Calin Daniel; Ringdalen, Inga Gudem; Dumoulin, Stephane; Hopperstad, Odd Sture (Journal article; Peer reviewed, 2016)
      A model of a polycrystalline material is studied, where each grain consists of several zones with different plastic properties. The size and configuration of the zones as well as their properties are mimicking the situation ...
    • Directionality and column arrangement principles of precipitates in Al-Mg-Si-(Cu) and Al-Mg-Cu linked to line defect in Al 

      Andersen, Sigmund Jarle; Marioara, Calin Daniel; Friis, Jesper; Bjørge, Ruben; Du, Qiang; Ringdalen, Inga Gudem; Wenner, Sigurd; Mørtsell, Eva Anne; Holmestad, Randi; Saito, Takeshi; Røyset, Jostein; Reiso, Oddvin (Journal article, 2016)
      In the structures of all metastable precipitates in Al-Mg-Cu and Al-Mg-Si alloys, we find that column surrounding of an element column in the needle/lath direction order according to simple principles. Advanced transmission ...
    • Early combination of material characteristics and toxicology is useful in the design of low toxicity carbon nanofiber 

      Jensen, Ellen K; Larsen, Sten Yngve; Nygaard, Unni Cecilie; Marioara, Calin Daniel; Syversen, Tore (Journal article; Peer reviewed, 2012)
      This paper describes an approach for the early combination of material characterization and toxicology testing in order to design carbon nanofiber (CNF) with low toxicity. The aim was to investigate how the adjustment of ...
    • Effect of Copper Addition on Precipitation Behavior near Grain Boundary in Al-Zn-Mg Alloy 

      Matsuda, Kenji; Yasumoto, Toru; Bendo, Artenis; Tsuchiya, Taiki; Lee, Seungwon; Nishimura, Katsuhiko; Nunomura, Norio; Marioara, Calin Daniel; Lervik, Adrian; Holmestad, Randi; Toda, Hiroyuki; Yamaguchi, Masatake; Ikeda, Ken-ichi; Homma, Tomoyuki; Ikeno, Susumu (Journal article; Peer reviewed, 2019)
      The effect of Cu-addition on age-hardening and precipitation have been investigated by hardness measurement, tensile test, high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning ...
    • Effect of copper addition on the cluster formation behavior of Al-Mg-Si, Al-Zn-Mg, and Al-Mg-Ge in the natural aging 

      Hatakeyama, Daichi; Nishimura, Katsuhiko; Matsuda, Kenji; Namiki, Takahiro; Lee, Seungwon; Nunomura, Norio; Aida, Tetsuo; Matsuzaki, Teiichiro; Holmestad, Randi; Wenner, Sigurd; Marioara, Calin Daniel (Journal article; Peer reviewed, 2018)
      The time-dependent resistivity of Al-Mg-Si(-Cu), Al-Zn-Mg(-Cu), and Al-Mg-Ge(-Cu) alloys are studied over a range of constant temperatures between 255 K and 320 K. The resistivity vs time curves for the samples show three ...
    • Effect of copper on fine precipitates at the early stage of aging in Al-Mg-X (X=Si, Ge, Zn) alloys 

      Matsuda, Kenji; Kawai, Akihiro; Watanabe, Katsumi; Lee, Seungwon; Marioara, Calin Daniel; Wenner, Sigurd; Nishimura, Katsuhiko; Matsuzaki, Teiichiro; Nunomura, Norio; Sato, Tatsuo; Holmestad, Randi; Ikeno, Susumu (Journal article, 2017)
      Age-hardenable Al–Mg–Si, Al–Mg–Ge, and Al–Zn–Mg alloys including Cu were investigated by transmission electron microscopy to understand extra diffraction spots that appear in their selected area electron diffraction patterns. ...