Speaker
Hanns Gietl
(Max-Planck-Institut für Plasmaphysik (IPP))
Description
Tungsten is a promising plasma facing material for future fusion reactors due to its unique property combination such as low sputter yield, high melting point and low activation. The main drawbacks for the use of pure tungsten are the brittleness below the ductile-to-brittle transition temperature and the embrittlement during operation e.g. by overheating and neutron irradiation. This limitation is mitigated by using tungsten fibre-reinforced tungsten composite (WfW) which utilizes extrinsic mechanisms to improve the toughness similar to ceramic fibre-reinforced ceramics. It was shown that this idea in principle works in the as-fabricated WfW as well as in the embrittled material. Recently a novel chemical vapour deposition process was developed allowing the production of large and reproducible samples [Riesch2016].
In this contribution we present a qualification program based on tensile tests on improved material samples produced with this new process. The material parameters were evaluated by means of displacement controlled “standard” tension test as well as low cycle fatigue (LCF) on as-fabricated and on embrittled samples. Standard tension tests give insight on the ultimate tensile strength and reveal the active toughening mechanisms provided by the fibres within the composite. However the expected loads on the material in a future fusion device are not only high steady state temperature but also extreme energy transients resulting in thermal cyclic loading of the material. Similar loading conditions are achieved in a low cycle fatigue test.
In the as-fabricated condition samples the material is still able to bear rising load despite multiple matrix cracks. Fibre necking as well as fibre pull out was observed leading to the typical pseudo ductile behavior of the composite. The description of the mechanical tests will be supplemented by detailed microstructural investigations.
[Riesch2016] Riesch et al., Proceedings of the 17th ICFRM, Nuclear Materials&Energy, 2016, submitted
Co-authors
Christian Linsmeier
(Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germany)
Hanns Gietl
(Max-Planck-Institut für Plasmaphysik (IPP), Boltzmannstrasse 2, 85748 Garching, Germany;Technische Universität München, Boltzmannstrasse 15, 85748 Garching, Germany)
Jan Willem Coanen
(Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), 52425 Jülich, Germany)
Johann Riesch
(Max-Planck-Institut für Plasmaphysik (IPP), Boltzmannstrasse 2, 85748 Garching, Germany)
Rudolf Neu
(Max-Planck-Institut für Plasmaphysik (IPP), Boltzmannstrasse 2, 85748 Garching, Germany)
Till Hoschen
(Max-Planck-Institut für Plasmaphysik (IPP), Boltzmannstrasse 2, 85748 Garching, Germany)
