Tungsten foil laminate for structural divertor applications – Tensile test properties of tungsten foil

This paper is the third part of our series on tungsten foil laminates. Within the tungsten laminate project we have succeeded in ductilizing tungsten by synthesizing a tungsten laminate made of tungsten foil, which is ductile. By assembling and joining several layers of tungsten foil, the ductile properties of the foil can be extended to the bulk.The aim of this paper is to present the results of tensile tests on 100-μm-thick tungsten foil in as-received and recrystallized conditions (1 h at 2000 °C). The results show that the mechanical properties of tungsten foil are anisotropic and can be explained by considering (i) the texture of the tungsten foil of {1 0 0}〈0 1 1〉, (ii) the anisotropic grain shape (0.5 μm × 3 μm × 15 μm), (iii) the preferred slip direction of body-centered cubic (bcc) metals, the 〈1 1 1〉 direction, as well as the preferred cleavage plane of tungsten at room temperature, the {1 0 0} plane. Furthermore, the results give further hints for the sources and mechanism of the extraordinary ductility of tungsten foil such as the ‘foil effect’, which is the dislocation annihilation at the free surface. In particular, the ductile material behavior of tungsten foil in the recrystallized condition seems to benefit from the foil effect and this is how a plastic strain of about 30% in a tensile test at 600 °C can be explained.