Microstructural investigation on tungsten for applications in future nuclear fusion reactors

Tungsten is a promising armour material for plasma facing components of nuclear fusion reactors. Two materials with different density and purity have been examined by optical microscopy, X-ray diffraction (XRD), instrumented indentation tests (FIMEC) and mechanical spectroscopy. For both the materials yield stress and elastic modulus strictly depend on the residual porosity. Moreover, the material with higher porosity (≈ 9%) is not stable and remarkable modulus variations are observed during heating. The IF spectrum exhibits a relaxation Q-1 peak superimposed to an exponentially increasing background. The peak is a single Debye peak with activation energy H = 74.86 kJ mol-1 and preexponential factor τ0 = 1.76 x 10-9 s that has been ascribed to dislocation interaction with intrinsic point defects (autointerstitial and substitutional).