Microstructure characteristics and properties of a novel Ni-based alloy for thermal neutron and gamma ray co-shielding

Abstract

A novel type of Ni-based alloy containing the gadolinium neutron absorption unit and the tungsten gamma ray shielding unit were successfully fabricated. The Ni5Gd formed was distributed along the grain boundary. W phase was precipitated when the W content reached 25 wt%, and Ni5Gd also precipitated along W phase rather than just along the grain boundary. The yield strength of the new alloy increased with Gd and W content, which was mainly attributed to solid solution strengthening and load transfer mechanism. The fracture elongation first dropped and then remained above 25% with the W content because the fracture pattern changed from intergranular fracture to a mixture of intergranular fracture and cleavage of W phase. The ultimate tensile strength of alloy with 18 wt% W and 2.5 wt% Gd can remain above 800 MPa at 400–600 °C. The absorption efficiency for thermal neutron of new alloys increased with the Gd content. The density of the new alloy could reach up to 10.86 g/cm3 with the W content which was close to that of plumbum, and the shielding efficiency for gamma ray increased. Our work provides new insights for achieving thermal neutron and gamma ray co-shielding alloys with integrated structure and function.