A MICROSTRUCTURAL EXPLANATION FOR IRRADIATION EMBRITTLEMENT OF V-15CR-5TI

[摘要] In order to explain severe degradation of mechanical properties, specimens of V-15Cr-5Ti have been examined by transmission electron microscopy following irradiation at 600-degrees-C to 14 dpa in FFTF. Specimens irradiated at 420 and 520-degrees-C were also examined to confirm density change measurements that indicated swelling levels as high as 2.5%. Following irradiation at 600-degrees-C, a complex microstructure was found that included a perfect dislocation network of line segments and loops, faulted loops, a high density of black spot damage and a high density of rod-shaped precipitates. Heat-to-heat variations did not appear to significantly alter these microstructural features; instead the density of large blocky precipitates, believed to be TiO2, was found to have increased with increasing oxygen content. Only two of the specimens irradiated at 600-degrees-C contained voids, whereas none of the specimens irradiated at 420 or 520-degrees-C contained voids. Therefore, swelling as measured by density change is probably due to phase instability in these specimen conditions, and the hardening and irradiation embrittlement that has been observed can be explained by the microstructural development. Phase stability appears to be an important criterion in the design of vanadium alloys for fusion applications.

[发布日期] 1991-12-01