My watch list  

Oxygen: A blessing and a curse for nanostructured alloying


Max-Planck-Institut für Eisenforschung GmbH

Dr. Jazmin Duarte did atom probe tomography measurements to characterize the sample and see the oxide distribution.

Severe plastic deformation and powder processing techniques are used to produce nanostructured materials with tailor-made compositions and without the effort of precasting. They allow the production of novel metallic nanocrystalline materials by mechanically alloying immiscible elements. Oxide contamination during the processing of these powders still hinders this method to be applied in industry comprehensively. Meanwhile it is also known that oxygen could be used beneficially to influence morphology, mechanical properties and thermal stability of nanostructured alloys. Up to now this possibility is still not used as it is unclear how oxide behaves during annealing. Scientists from the Max-Planck-Institut für Eisenforschung (MPIE), the Austrian Erich Schmid Institute of Material Science, the Universities Leoben and Graz (Austria) and the Chinese Hubei University analysed in-situ copper-iron alloys during annealing to find out when and how oxide is formed and how it can be used to strengthen nanocrystalline materials.

“By combining different experimental methods and density-functional theory calculations, we studied the thermal behaviour of oxygen in nanocrystalline copper-iron alloys which were fabricated under severe deformation and high pressure. During the heating process but still at very low temperatures, oxidation starts, leading to the formation of nanosized copper and iron oxides inside grains. Later in the heating process the metastable copper-iron solid solution decomposes into iron- and copper-rich phases.”, explains Dr. Jazmin Duarte, senior researcher in the department “Structure and Nano-/Micromechanics of Materials”. The copper and iron oxides and iron precipitates grow with annealing temperature, till they reach approximately 10 nanometres. Both oxide distributions are almost identical, which means that oxygen diffuses to one specific area during heating, simultaneously triggering the nucleation processes of oxides. “For the first time a direct observation of oxide formation in single-phase copper-iron alloys was possible. We also did several comparison studies and ex situ analyses to make sure that neither the electron beam of the transmission electron microscope nor the sample size have an influence on the oxidation and precipitation processes. This new insights give us the possibility of manipulating mechanical properties by including oxygen into nanocrystalline alloys. Oxygen which was formerly seen as contamination to be avoided, can now be used as an ingredient to form advanced, nanostructured alloys.”, explains Prof. Gerhard Dehm, director at the MPIE.

The scientists are now further studying the mechanisms by which oxygen can be introduced into the alloys and how the microstructure and consequently the mechanical behaviour are affected by an increased content of dissolved oxygen. Such tailor-made microstructures could be then used to engineer oxide strengthened nanocrystalline materials for specific applications.

Facts, background information, dossiers
More about MPI für Eisenforschung
  • News

    Atomistic Insights into Electrocatalysis

    Electrocatalysts are important for many industrial processes as they enhance the conversion of electrical energy into chemical energy and thus help to store excessive electrical energy generated by renewable energy resources. Hydrogen is expected to be crucial for the storage of chemical en ... more

    Atomic Design by Water

    A central element in such diverse technological problems as corrosion protection, battery materials or hydrogen production via electrolysis or fuel cells is the contact between two conducting elements – the electrolyte and the solid electrode at which a voltage is applied. Despite its impor ... more

    Gum metals pave the way for new applications

    Metals which can be bent as gum pave the way for new industrial applications for example in the aerospace industry. These so-called gum metals exist but the mechanism behind this behaviour was still unsettled and thus difficult to be used for applications. Scientists from the Max-Planck-Ins ... more

More about Max-Planck-Gesellschaft
  • News

    Wendelstein 7-X achieves world record

    In the past experimentation round Wendelstein 7-X achieved higher temperatures and densities of the plasma, longer pulses and the stellarator world record for the fusion product. Moreover, first confirmation for the optimisation concept on which Wendelstein 7-X is based, was obtained. Wende ... more

    Light-induced superconductivity under high pressure

    A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on ... more

    Molecules Brilliantly Illuminated

    Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of health. Researchers at the Laboratory for Attosecond Physics (LAP) – a joint venture between Ludwig-Maximilians-Universität (LMU) and ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE