抄録
Effect of Cu addition on microstructure was investigated in Fe-Cr-Cu martensitic alloys by means of optical and transmission electron microscopy, and X-ray diffractometry. Lath-martensitic single structure can be obtained in 9mass%-Cu steels water-quenched from the solution treatment temperature of 1273K. The morphology of martensite-laths is independent of Cu content in the steels with 4 mass% Cu or less. Dislocation density in martensitic structure, however, is enhanced with increasing Cu content. On the solution treatment, Cu atoms markedly segregate at austenite grain boundary, and the Cu content increases to about 50 at% (53 mass%) in the case of 9 mass% Cr-4 mass% Cu steel. This results in the retardation of grain growth of austenite at the solution treatment temperature probably due to the grain boundary dragging effect by Cu atoms and/or the decrease in grain boundary energy. The austenite grain refining by Cu addition also causes the refining of sub-structure within prior austenite grains; martensite-block and -packet structure.
