Crystallography and interphase boundary of (MnS + VC) complex precipitate in austenite

Abstract

Crystallography and interphase boundary of (MnS ϩ VC) complex precipitates formed in austenite (␥) matrix are studied by transmission electron microscopy (TEM) in an austenitic Fe-36 mass pct Ni alloy containing small amounts of manganese, sulfur, vanadium, and carbon. When VC is formed directly within the ␥ matrix grain, it displays a cube-cube orientation relationship (OR) with respect to ␥. When VC is formed on MnS, which precipitated in ␥ with a cube-on-edge OR, three distinctive VC/␥ ORs are found: (1) , (2) the cube-cube OR, and (3) the cubeon-edge OR. The MnS/␥ OR becomes irrational after ␥ recrystallization. When VC forms on such incoherent MnS particles, which hold irrational ORs with respect to ␥ matrix, a wide variety of VC/␥ ORs are observed. Geometrical analysis by near coincidence site lattice (NCS) model achieves reasonable success in explanation of the observed planar facets for VC precipitates having rational ORs with respect to ␥. However, as for the VC formed on the incoherent MnS with irrational ORs, there is rather poor agreement between observation and prediction.(111) g // (001) VC , [11 0] g //[11 0] VC

Dependence of Elevated Temperature Intergranular Cracking on Grain Size and Bulk Sulfur Content in TP347H Austenitic Stainless Steels

“…The round-shaped MnS precipitates are denser in the HS steel of the higher sulfur content. As reported in a research, 20) the MnS precipitate and the NbC carbide are formed as a complex precipitate. size, which are shown in Figs.…”

“…5(b). If the previous system 20) which reports the coherent MnS precipitation in the Fe-36%Ni austenite matrix are considered, such the lower grain boundary segregation concentration of sulfur and the resulting longer time to failure may not be expected in the HS steel.…”