Intergranular fracture induced by helium bubbles segregation in NiFe single-phase concentrated solid solution alloys

Single-phase concentrated solid solution alloys (SP-CSAs) are potential nuclear structural materials with excellent irradiation resistance. Under irradiation environment, helium (He) atoms are easily segregated and stored at grain boundaries (GBs), thus causing He embrittlement of materials. The intergranular fracture behavior of NiFe SP-CSAs caused by He bubbles segregation is studied with molecular dynamics (MD) method. The effects of Fe atom concentration, GB type and He atom number in He bubbles on the intergranular fracture are analyzed. Since the disordered atoms impede crack initiation and propagation, NiFe SP-CSAs exhibit stronger fracture resistance than pure Ni. With the increase of strain, the number of disordered atoms at the GB increases further, so that the fracture strain of NiFe SP-CSAs with symmetric tilt GB decreases. With the increase of Fe atom concentration, Fe atoms inhibit the intergranular crack initiation and propagation in NiFe SP-CSAs more powerfully. In addition, the increase of the He atom number in the He bubble promotes the fracture. The formation of SP-CSAs is also beneficial to enhancing intergranular fracture resistance of alloys with twist GBs and asymmetrically tilt GBs, and the impact on the latter is more pronounced.