Mechanical Property Changes of Tungsten after Helium Ion Irradiation with Different Damage Degree

The surface of recrystallized tungsten was irradiated by helium ions with different energy and ion fluence. The microstructure of tungsten with irradiation damage of 0.2,0.5,1.0 dpa was observed. The nanoindentation test was conducted with spherical indenter of different radius (1,5,10 μm) to obtain the indentation stress-strain curve, and the change of mechanical properties and reason for the change were explored. The results show that the thickness of damage layer on tungsten surface was 554-558 nm after irradiation with different damage degree. With increasing damage degree, the density of dislocation loop in tungsten increased obviously. The indentation stress-strain curves of tungsten after irradiation did not exhibit pop-in phenomenon, and the yield strength increased with damage degree, and the indentation elastic modulus basically unchanged. The dislocation loop defect caused by irradiation was the direct cause of the change of mechanical properties of tungsten. The mechanical properties of tungsten had the effect of indentation size. The smaller the indenter radius, the higher the yield strength of tungsten, and the greater the indentation stress when the stress-strain curve of unirradiated tungsten showed pop-in.