title: In-situ Observation of Cross-Sectional Microstructural Changes and Stress Distributions in Fracturing TiN Thin Film during Nanoindentation.
abstract: Load-displacement curves measured during indentation experiments on thin films depend on non-homogeneous intrinsic film microstructure and residual stress gradients as well as on their changes during indenter penetration into the material. To date, microstructural changes and local stress concentrations resulting in plastic deformation and fracture were quantified exclusively using numerical models which suffer from poor knowledge of size dependent material properties and the unknown intrinsic gradients. Here, we report the first in-situ characterization of microstructural changes and multi-axial stress distributions in a wedge-indented 9 μm thick nanocrystalline TiN film volume performed using synchrotron cross-sectional X-ray nanodiffraction. During the indentation, needle-like TiN crystallites are tilted up to 15 degrees away from the indenter axis in the imprint area and strongly anisotropic diffraction peak broadening indicates strain variation within the X-ray nanoprobe caused by gradients of giant compressive stresses. The morphology of the multiaxial stress distributions with local concentrations up to -16.5 GPa correlate well with the observed fracture modes. The crack growth is influenced decisively by the film microstructure, especially by the micro- and nano-scopic interfaces. This novel experimental approach offers the capability to interpret indentation response and indenter imprint morphology of small graded nanostructured features.
authors.affiliation: Materials Center Leoben Forschung GmbH, Leoben, Austria.
authors.forename: Angelika
authors.initials: A
authors.lastname: Zeilinger
authors.affiliation: Department of Materials Physics, Montanuniversität Leoben, Austria.
authors.forename: Juraj
authors.initials: J
authors.lastname: Todt
authors.affiliation: Ruprecht Haensel Laboratory, University of Kiel, Germany.|Helmholtz Zentrum Geesthacht, Geesthacht, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Krywka
authors.affiliation: Helmholtz Zentrum Geesthacht, Geesthacht, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Müller
authors.affiliation: Materials Center Leoben Forschung GmbH, Leoben, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Ecker
authors.affiliation: Materials Center Leoben Forschung GmbH, Leoben, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Sartory
authors.affiliation: Department of Materials Physics, Montanuniversität Leoben, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Meindlhumer
authors.affiliation: Materials Center Leoben Forschung GmbH, Leoben, Austria.
authors.forename: Mario
authors.initials: M
authors.lastname: Stefenelli
authors.affiliation: Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Austria.
authors.forename: Rostislav
authors.initials: R
authors.lastname: Daniel
authors.affiliation: Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Mitterer
authors.affiliation: Helmholtz Zentrum Geesthacht, Geesthacht, Germany.
authors.forename: Jozef
authors.initials: J
authors.lastname: Keckes