Microstructural changes induced in advanced tungsten grades under high temperature neutron irradiation

Recent studies addressing the change of mechanical properties after high temperature irradiation of tungsten
have reported substantial increase of the ductile to brittle transition temperature as well as increase of the
hardness. In this work, we performed microstructural analysis by means of transmission electron microscopy
(TEM) on various tungsten grades earlier exposed to high temperature neutron irradiation at 1200 ◦C up to 1 dpa.
The latter corresponds to the expected irradiation temperature on the surface of a tungsten monoblock during the
steady state operation in ITER. TEM was applied to five tungsten (W) materials including ITER specification pure
W and precipitate strengthened W alloys. The analysis of TEM data coupled with its discussion led to a number of
important conclusions regarding the damage induced at 1200 ◦C neutron irradiation such as: (i) weak effect of
recrystallization on the accumulation of the lattice damage; (ii) promising results on the tolerance of damage
accumulation in W-Y2O3 grade and (iii) internal oxidation of TiC particles which may contribute to the huge
increase of the irradiation induced hardening.