G. Korb (Sp), G. Kladler, Austrian Research Centers GmbH, Seibersdorf (Austria)
The ODS-Alloy (PM 1000, PM 2000, PM 1500)
(ODS .... Oxide Dispersion Strengthened)
are mainly used in a very coarse-grained condition after a secondary recrystallisation. Such grains can be as large
as centimeters and - in length - even meters.
Nevertheless during their production route they run through a status of “fine grained” microstructure because of
their permanent deformation under hot or semi-hot temperatures and multiple dynamic recrystallisation. Only the
final secondary recrystallisation step at temperatures close to the melting point lead to the described coarse
structure.
The presented work intended to achieve an extremely fine structure starting from the “as worked” condition via a
so called “Severe Plastic Deformation” (SPD)
SPD is a deformation of a metal or alloy by extremely high loads, enforced shear deformations under high
isostatic pressure within very specific tools. The deformation temperatures are kept relatively low not to provoke
recrystallisation “in situ”.
One of the well-known methods is “Equal Channel Angular Pressing” (ECAP) whereby the metallic sample is forced
to pass a rectangular bended channel at the minimum for several passes.
For ODS-Alloys, the methodology “ECAP”, used for light metals, Copper and other easy-to-deform-alloys had to
be adapted and approved. ODS alloys are severe to deform and exhibit a rather high deformation resistance.
Finally the authors succeeded in deformation of PM2000 (Fe-based ODS alloy) in the fine grained status ( ~ 1-2
μm grain size) at moderate temperatures. The characterisation of the samples gave a significant increase in RT
hardness (RT strength) and a sensibility versus relatively mild heat-treatments (hardness decrease!).
A significant decrease of grain – size down to 100 – 300 nm could be observed in TEM pictures. Detailed
characterisation of the mechanical properties (ductility) are under way, a potential application of such materials
tough modified in composition could be found in severe radiation and heat loaded parts e.g. in Fission and Fusion
Reactors.
Remark: The work performed for this publication has been carried out mostly in the frame of the integrated
Project “EXTREMAT”, financielly supported by the EU, Project Nr. 500253-2. The authors are grateful for this
support.