Effects of Alloy Composition and Processing on the Microstructure of D-9 Type Stainless Steel. Final Report

摘要

The effects of composition modifications of Type 316 stainless steel on the constitution and microstructural stability during extended exposure to elevated temperature has been studied. Conventional TEM, (CTEM), Analytical TEM (STEM) and ultra-high resolution TEM have been used. It has been found that several relatively coarse, heterogeneously distributed constituents including Laves and G phases, TiN and M sub 23 C sub 6 can form in addition to a fine, uniform distribution of MC. In the present case, the MC is TiC. The detailed nature of the latter constituent and its relationship to the fcc gamma matrix have been examined in detail. The results of CTEM are conflicting in that the electron diffraction evidence suggests that the particles should be semicoherent or noncoherent, whereas the images of the MC: gamma interfaces show no structure in the form of ledges or misfit dislocations. Ultra-high resolution TEM showed that the lattice planes were continuous through the matrix and the TiC particles. These results suggest that the TiC is coherent despite the large mismatch between the lattices. This finding has significant bearing on the role of the TiC: gamma interfaces as He sinks in fast neutron environments. 12 figures. (ERA citation 09:002678)