TEM analysis of fine sulphides dissolution and precipitation in steel

Results of transmission electron microscopy (TEM) investigation of morphology, size distribution and chemistry of nano-inclusions formed in 4 mm thick laboratory steel ingots in as-cast condition and after heat treatment are reported. The investigated steel contained 0.11–0.14 C, 0.6 Mn, 0.25 Si, 0.22 Cu, 0.025–0.037 S (wt.%), and 80–115 ppm O and solidified at an average cooling rate of 250 K s−1. In the as-cast specimens most nano-inclusions had a diameter in the range 10–100 nm with an average size of 30 nm. They were identified by microanalysis in thin foils as sulphides: MnS, (Mn,Cu)S, CuS and Cu2S. After a solution treatment of the thin ingots the re-precipitation of nano-sulphides was investigated.