The tensile properties and fracture toughness of a Zr3Al-based alloy after fast neutron irradiation

The effect of fast neutron irradiation at 600 deg K on the tensile properties and fracture toughness of a Zr3Al-based alloy (Zr--8.6 wt.-% Al) has been studied for fluences up to 2.4 x 1025 n/m2 (E > 1 MeV). For neutron fluences # < 1025 n/m2, the plastic elongation decreases with increasing fluence. Above this fluence, all the Zr3Al specimens exhibit an elastic response with no ductility, i.e. they fail in a brittle manner. Correspondingly, the fracture toughness decreases with increasing neutron fluence from a value of 73 MPa.m1/2 for the unirradiated materials to a low of 0.44 to 7.1 MPa.m1/2 for specimens irradiated to a fluence of 2.3 x 1025 n /m2. These values confirm that, under fast neutron irradiation, the Zr3Al becomes as brittle as glass. The complete loss of ductility, loss of strength and decrease in fracture toughness for neutron fluences > 1025 n/m2 are explained in terms of irradiation-induced disordering/amorphousness of the Zr3Al intermetallic.23 refs.--AA