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@PHDTHESIS{Sjoegren:618891,
      author       = {Sjoegren, Elis},
      othercontributors = {Ahadi, Aylin and Orlov, Dmytro and Lenrick, Filip},
      title        = {{I}n situ {C}haracterization of {D}eformation {M}echanisms
                      in {H}armonic {S}tructure {N}ickel},
      school       = {Lund University},
      type         = {Dissertation},
      reportid     = {PUBDB-2024-07213},
      isbn         = {978-91-8104-256-6},
      pages        = {91},
      year         = {2024},
      note         = {I do not want the fulltext to be published in the DESY
                      Library as I want to direct traffic to the Lund University
                      website.; Dissertation, Lund University, 2024},
      abstract     = {There is an ever-increasing demand for structural metals
                      with higher strength. Metals can be strengthened by reducing
                      grain size in their microstructure, but ductility is also
                      concomitantly reduced. High strength and ductility are a
                      desirable combination of properties for most structural
                      engineering materials. By arranging fine grains in a
                      continuous network that surrounds islands of coarse grains,
                      in a so-called harmonic structure, it is possible to
                      increase the strength without reducing ductility. Such a
                      synergetic effect has been attributed to an accelerated
                      work-hardening rate in harmonic structures.This thesis aims
                      at deepening the understanding of the synergetic effects,
                      which can help the optimization of harmonic structures in
                      the future. The distributions of stress and strain were
                      measured during tensile testing as they are deemed important
                      for understanding the interplay between coarse and fine
                      grain fractions. Stress distribution among the grain
                      fractions were measured at unprecedented detail in harmonic
                      structures materials through synchrotron X-ray powder
                      diffraction and individual grains through high resolution
                      reciprocal space mapping. To achieve individual
                      investigation of grain fractions, a new algorithm was
                      elaborated in this work for the separation and analysis of
                      diffraction data in a single- phase material with two
                      fractions of grain sizes. The distribution of strain was
                      measured with digital image correlation in optical
                      microscopy.The main achievements in this work reveal that
                      the constriction of coarse grains by fine grains in harmonic
                      structures increases the yield strength of coarse grains
                      compared to homogenous counterparts. At elastic-plastic
                      transition, stress partitions between the grain fractions
                      and back stresses develop in coarse grains along with
                      forward stresses in fine grains. With further macroscopic
                      strain, the local strains also clearly partition between the
                      grain fractions. The stress-strain behaviour of the grain
                      fractions is similar to the homogenous counterparts when the
                      local and macroscopic strains are similar. The high
                      work-hardening rate of the harmonic structure is the
                      superposition of fine grains with inherited high
                      work-hardening rate and coarse grains with low
                      work-hardening rate. Beyond elastic-plastic transition, the
                      acceleration of work-hardening rate in the coarse-grained
                      fraction is found, which coincides with the strain
                      partitioning. The evolution of strain distributions shortly
                      before macroscopic fracture indicates that the
                      microstructure might suppress strain localization. However,
                      full understanding of fracture mechanisms requires further
                      investigation.},
      cin          = {DOOR ; HAS-User / LUND},
      cid          = {I:(DE-H253)HAS-User-20120731 / I:(DE-H253)LUND-20191211},
      pnm          = {6G3 - PETRA III (DESY) (POF4-6G3) / FS-Proposal: I-20170726
                      EC (I-20170726-EC) / FS-Proposal: I-20190991 EC
                      (I-20190991-EC) / SWEDEN-DESY - SWEDEN-DESY Collaboration
                      $(2020_Join2-SWEDEN-DESY)$},
      pid          = {G:(DE-HGF)POF4-6G3 / G:(DE-H253)I-20170726-EC /
                      G:(DE-H253)I-20190991-EC /
                      $G:(DE-HGF)2020_Join2-SWEDEN-DESY$},
      experiment   = {EXP:(DE-H253)P-P07-20150101 /
                      EXP:(DE-H253)P-P21.2-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://bib-pubdb1.desy.de/record/618891},
}