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Keynote Lecture

WEB Ultrafine-grained dispersoid-strengthened aluminum alloys for applications at elevated temperatures produced by high-energy milling

Tuesday (22.09.2020)
16:10 - 16:40 S: Structural Materials 1
Part of:

Most engineering alloys show a substantial deterioration of the mechanical properties when being applied at elevated temperatures, e.g. in process engineering, power generation or mobility. This is attributed to creep degradation and the gradual disappearance of the hardening effects by grain refining and strengthening precipitates. By introducing small-sized non-metallic dispersoids by mechanical alloying, coarsening and grain boundary migration can be hindered effectively.

In the present work, aluminum alloy powders (Al5083, Al2024, Al7075) were mechanically alloyed by high-energy ball milling in combination with non-metallic zinc ferrite spinel (ZnFe2O4). After hot isostatic pressing (HIP) of the resulting flake-shaped particles, the materials are hot extruded and machined to cylindrical tensile, fatigue and creep specimens. It was shown that the ultrafine-grained materials, with an average grain size of 250nm, exhibit superior mechanical properties under monotonic and cyclic loading conditions. As compared to the respective bulk materials, the yield strength was increase substantially at sufficient ductility (up to 10% elongation at fracture). The ultrafine-grained structure is maintained at elevated temperature due to the presence of very small ceramic particles that effectively pin the alloy grain boundaries. This leads to a promising creep response of the aluminum materials at temperatures up to 300°C.

Additional Authors:
  • Dr. Katrin Jahns
    RWTH Aachen University
  • Michael Harwarth
    University of Applied Sciences Osnabrück