TEM analysis of centreline sulphide precipitates modified by titanium additions to low carbon steel

Elongated inclusions, particularly MnS, contribute significantly to reduced ductility and toughness in hot rolled steel but earlier research indicated that these properties can be improved by titanium additions. Such additions to a steel result in titanium being dissolved in manganese sulphide or MnS being replaced by TiS and/or titanium carbosulphides. In the present study, a steel was designed to decrease alloying element segregation and to evaluate the effect of titanium on centreline sulphide precipitates. Precipitates were identified by using scanning electron microscopy and characterized by the use of transmission electron microscopy following sample preparation by focused ion beam milling techniques. Iron–titanium-sulphides form in close proximity to MnS precipitates that contain iron. Evidence is provided that an increase in the titanium content of steel leads to an increase in the percentage of titanium contained in the iron sulphides and a decrease in the iron content of MnS inclusions.