Influence of Ti on Inclusion Formation of Reduced Activation Ferritic/Martensitic Steels

Abstract

Reduced activation ferritic/martensitic steels (RAFs), such as F82H (Fe 8Cr 2W 0.2V 0.04Ta 0.1C), are the leading candidates for structural materials of fusion reactors, and it is essential for the development of RAFs to assure its good for fusion application. In this study, the influence of Ti on impact property was studied based on microstructural analyses and charpy impact tests which were performed in general purity F82H (0.004Ti 0.0060N) and high purity F82H (＜0.001Ti 0.0014N). In general purity F82H, its impact property around DBTT showed both 100 brittle fracture and brittle ductile, and this tendency did not appear in high purity F82H. SEM observation on those brittle fracture surfaces of general purity F82H revealed the presence of Al 2 O 3  Ta(V, Ti)O composite oxides at the fracture initiation point. The size distribution analyses of oxides indicate that the complex oxide in general purity F82H showed a higher number density than in high purity F82H. In addition to this, EDS analyses showed that complex oxides in general purity F82H had a strong peak of Ti, but they were not detected in the oxides in high purity F82H. These results suggest that Ti has a significant influence on the formation of oxides, which in turn affects impact property.