Effects of heat treatments and neutron irradiation on the physical and mechanical properties of copper alloys at 100 deg. C

The final irradiation experiment in a series of screening experiments aimed at investigating the effects of bonding and bakeout thermal cycles on irradiated copper alloys is described herein. Tensile specimens of CuCrZr and CuNiBe alloys were given various heat treatments corresponging to solution anneal, prime-ageing and bonding thermal treatment.

Additional specimens were reaged and given a reactor bakeout treatment at 350 deg. C for 100 h. GlidCop"T"M CuAl-15 (previously referred to as CuAl-25) was given a heat treatment corresponding to a bonding thermalcycle only. Specimens were neutron irradiated at 100 deg. C to a dose level of #approx#0.3 dpa in the DR-3 reactor at Risø National Laboratory.

Post-irradiation tensile tests at (100 deg. C), electrical resistivity measurements (at 23 deg. C), and microstructural examinations were performed. Testing and analysis of the unirradiated specimens have been reported earlier, and will only be referred to when necessary. The post-irradiation tests at 100 deg.

C revealed that the greatest loss of ductility occurred in the CuCrZr alloys irradiated at 100 deg. C, irrespective of the preirradiatios heat treatment, with the uniform elongation dropping to levels of less than 1.5%. The yield and ultimate strengths for all of the individual heat treated samples increased substantially after irradiation.

The same trend was observed for the CuNiBe alloys, which exhibited much higher uniform elongation and strength after irradiation than that observed in the case of CuCrZr alloys. In both alloys irradiation-induced precipitation lead to a large increase in the strength of the solution annealed specimens with a noticeable decrease in uniform elongation.

The CuAl-25 alloy also experienced an increase in the overall strength of the alloy after irradiation, accompanied by approximately a 50% decrease in the uniform and total elongation.