• 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 ...
    • 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 ...
    • 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 ...
    • 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 ...
    • 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 ...
    • 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 ...
    • 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 ...
    • Effect of room temperature storage time on precipitation in Al-Mg-Si(-Cu) alloys with different Mg/Si ratios 

      Wenner, Sigurd; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmestad, Randi (Journal article; Peer reviewed, 2012)
      The effect of natural ageing time before artificial ageing has been investigated in four Al – Mg – Si(– Cu) alloys, with 0.4 % Mg + 0.8 % Si and 0.8 % Mg + 0.4 % Si, both with and without 0.14 at.% Cu. The precipitate ...
    • Effects of Germanium, Copper, and Silver Substitutions on Hardness and Microstructure in Lean Al-Mg-Si Alloys 

      Mørtsell, Eva Anne; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Røyset, Jostein; Reiso, Oddvin; Holmestad, Randi (Journal article; Peer reviewed, 2015)
      It is shown that strength loss in a 6060 Al-Mg-Si alloy caused by reduction in solute can be compensated by adding back smaller quantities of Ag, Ge, and Cu. Nine alloys were investigated. Ge was found to be the most ...
    • Elemental electron energy loss mapping of a precipitate in a multi-component aluminium alloy 

      Mørtsell, Eva Anne; Wenner, Sigurd; Longo, Paulo; Andersen, Sigmund Jarle; Marioara, Calin Daniel; Holmestad, Randi (Journal article, 2016)
      The elemental distribution of a precipitate cross section, situated in a lean Al-Mg-Si-Cu-Ag-Ge alloy, has been investigated in detail by electron energy loss spectroscopy (EELS) and aberration corrected high angle annular ...
    • HAADF-STEM and DFT investigations of the Zn-containing β'' phase in Al-Mg-Si alloys 

      Saito, Takeshi; Ehlers, Flemming J H; Lefebvre, Williams; Hernandez-Maldonado, D; Bjørge, Ruben; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmestad, Randi (Journal article, 2014)
      The Zn-containing β″ phase in Al–Mg–Si alloys was investigated by aberration corrected high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), combined with density functional theory (DFT) ...
    • How calcium prevents precipitation hardening in Al–Mg–Si alloys 

      Wenner, Sigurd; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmestad, Randi (Journal article, 2013)
      We have investigated the effect on precipitate microstructure and hardness upon adding small amounts of Ca to a base Al–Mg–Si alloy. The main investigative techniques were transmission and scanning electron microscopy. We ...
    • Improving ageing kinetics and precipitation hardening in an Al-Mg-Si alloy by minor Cd addition 

      Qian, Feng; Mørtsell, Eva Anne; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Li, Yanjun (Journal article; Peer reviewed, 2018)
      This study reports significant improvements in both the age hardening kinetics and peak hardness of an Al-Mg-Si alloy by microalloying with 0.06 at% Cd. A detailed high-angle annular dark-field scanning transmission electron ...
    • Modeling over-ageing in Al-Mg-Si alloys by a multi-phase CALPHAD-coupled Kampmann-Wagner Numerical model 

      Du, Qiang; Tang, Kai; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmedal, Bjørn; Holmestad, Randi (Journal article, 2017)
      The formation of the equilibrium precipitation phase during ageing treatment of Al-Mg-Si alloys is preceded by a series of metastable phases. Given longer ageing time, higher ageing temperature or elevated temperature ...
    • 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 ...
    • 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 in an Al-Mg-Cu alloy and the effect of a low amount of Ag 

      Mihara, Mami; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmestad, Randi; Kobayashi, Equo; Sato, Tatsuo (Journal article, 2016)
      Two high-purity aluminium alloys based on composition Al–3.0Mg–1.0Cu (wt%), one with added 0.4 wt% Ag, were compared up to 11 days ageing at 443 K by means of transmission electron microscopy and hardness measurements. The ...
    • Structural investigation of precipitates with Cu and Zn atomic columns in Al-Mg-Si alloys by aberration-corrected HAADF-STEM 

      Saito, Takeshi; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Lefebvre, Williams; Holmestad, Randi (Journal article; Peer reviewed, 2014)
      Precipitates in Al-Mg-Si alloys with Cu addition (~0.1 wt%) and Zn addition (~1 wt%) were investigated by aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Most ...
    • Structural modifications and electron beam damage in aluminium alloy precipitate θ'-Al2Cu 

      Wenner, Sigurd; Friis, Jesper; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Holmestad, Randi (Journal article, 2015)
      The –AlCu phase in an Al–4Zn–2Cu–1Mg–0.7Si (wt.%) alloy was investigated by means of scanning transmission electron microscopy. With our specific alloy composition, the phase is often formed with stacking faults on and ...
    • The effect of Cu and Ge additions on strength and precipitation in a lean 6xxx aluminium alloy 

      Mørtsell, Eva Anne; Marioara, Calin Daniel; Andersen, Sigmund Jarle; Røyset, Jostein; Reiso, Oddvin; Holmestad, Randi (Journal article; Peer reviewed, 2015)
      It has been demonstrated that the strength loss in a lean Al-Mg-Si alloy due to solute reduction could be compensated by back-adding a lower at % of Ge and Cu. Nanosized precipitate needles which are the main cause of ...