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Magnetic thin film enables early detection of wear and corrosion in nonmagnetic metals
August 08, 2018
Source: ASM international
Researchers from the Technical University of Kaiserslautern and Johannes Gutenberg-University, Mainz, both of Germany, announce that they have developed a magnetic coating material that enables early detection of signs of wear, corrosion, and fatigue in nonmagnetic steel as well as other materials such as aluminum.
Described in the Journal of Magnetism and Magnetic Materials, the method involves application of a thin magnetic layer to the nonmagnetic metal, allowing microstructural changes to be detected using magnetic effects. The technique applies magnetic films, each 20 nanometers thin, consisting of terfenol-D (an alloy of terbium, iron, and dysprosium), or permalloy, a nickel-iron compound.
A Kerr microscope (shown in the photo) is then used to check whether strains in the steel can be detected. The “Kerr effect” allows the magnetic microstructures, the so-called domains, to be imaged by rotating the polarization direction of light. "Microscopic strain in nonmagnetic steel causes the direction of magnetization of the thin layer to change,” explains Dr. Martin Jourdan from the Institute of Physics at the JGU. The process provides much earlier detection than conventional methods.
M. Jourdan et al., “Strain detection in non-magnetic steel by Kerr-microscopy of magnetic tracer layers,” Journal of Magnetism and Magnetic Materials (2018).
Materials Testing and Evaluation | Failure Analysis
Materials Testing and Evaluation | Materials Characterization
Metals and Alloys | Aluminum
Metals and Alloys | Stainless Steels