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@PHDTHESIS{Weidt:785507,
      author       = {Weidt, Moritz Rudolf Martin},
      othercontributors = {Bührig-Polaczek, Andreas and Dahle, Arne K.},
      title        = {{M}icroporosity characteristics in {A}l-{S}i foundry
                      alloys},
      volume       = {27},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {Gießerei-Institut der RWTH Aachen},
      reportid     = {RWTH-2020-03260},
      isbn         = {978-3-944601-16-8},
      series       = {Ergebnisse aus Forschung und Entwicklung},
      pages        = {1 Online-Ressource (XXI, 231 Seiten) : Illustrationen,
                      Diagramme},
      year         = {2020},
      note         = {Auch veröffentlicht auf dem Publikationsserver der RWTH
                      Aachen University; Dissertation, RWTH Aachen University,
                      2020},
      abstract     = {Although the importance of aluminium as a material for a
                      broad variety of technical applications is already very
                      high, the general trend of weight reduction in the mobility
                      sector has the potential to boost the application of
                      aluminium in structural components as well as in housings,
                      covers and the powertrain even further. The aluminium cast
                      process is and remains a very competitive process to produce
                      highly complex and integrated, near-net-shape components up
                      to very large production volumes. This is true, although the
                      capability to predict and thus control the amount and size
                      of microporosity is still worthy of improvement. To achieve
                      better control of microporosity, a better understanding of
                      the causes, the nucleation, the growth, and the final
                      characteristics of microporosity in aluminium cast alloys
                      are necessary. This work aims to expand and deepen the
                      understanding and knowledge of microporosity by looking at
                      the fundamental principles of solidification, and the
                      evaluation of almost 100 micro XCT scans taken from
                      industrial production and laboratory casting experiments. A
                      pore volume-weighted approach is applied to enable the
                      comparison of XCT data generated at three different spatial
                      resolutions. The weighing procedure leads to linear
                      correlations between average porosity and the maximum and
                      mean pore volume and size for up to four characteristic
                      specimen populations. The four different specimen
                      populations can be related to the hydrogen content as well
                      as the local cooling rate. At low hydrogen levels, the
                      differences in solidification morphology due to chemical
                      composition determine the amount of average porosity. The
                      maximum pore size increases strongly with average porosity,
                      and only very low local cooling rates change the observed
                      low sphericity pore morphology. At high hydrogen levels, the
                      sensitivity of the mean and maximum pore volume and size is
                      lower in respect to average porosity, and the local cooling
                      rate strongly affects the observable high sphericity pores.
                      In the transition zone between low and high hydrogen levels,
                      a mixture of high and low sphericity pores can be observed.
                      For low hydrogen levels, the analysis of the mean pore
                      sphericity shows a constant drop with increasing average
                      porosity. At medium to high hydrogen levels samples show a
                      constant and high mean sphericity value. A single linear
                      relation between the mean and maximum pore volume
                      respectively the mean and maximum pore size can be
                      established. These correlations are independent of all
                      varied experimental parameters and therefore constitute a
                      new and fundamental characteristic of microporosity in
                      aluminium cast alloys. The presented findings improve the
                      understanding of the characteristics of microporosity and
                      allow the prediction of important pore distribution
                      measures. The developed correlations will find application
                      in the Integrated Computational Materials Engineering (ICME)
                      approach and are the first step in a through process
                      modelling framework.},
      cin          = {526110 / 520000},
      ddc          = {620},
      cid          = {$I:(DE-82)526110_20140620$ / $I:(DE-82)520000_20140620$},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      doi          = {10.18154/RWTH-2020-03260},
      url          = {https://publications.rwth-aachen.de/record/785507},
}