Effects of sulphur on hot ductility of low-carbon steel austenite

AbstractThe hot ductility of low-carbon austenite has been studied in order to reveal the hot-cracking mechanism related to sulphur segregation and sulphide precipitation during solution treatment and deformation. Ductility was greatly reduced during high-strain-rate tensile deformation in the temperature range 1073-1373 K. Fracture occurred via a typical intergranular mode, characterized by both shallow dimples caused by microvoid coalescence and rather smooth facets caused by intergranular decohesion. The former morphology is a result of the dense precipitation of sulphides, identified as Fe-rich (Fe, Mn) S, on the austenite grain boundaries. Finely dispersed sulphide particles within the grains and the existence of precipitate-free zones along grain boundaries enhanced strain localization in the vicinity of the boundaries during deformation. The intergranular decohesion arises from the decrease in grain-boundary strength produced by sulphur segregation. Hot ductility is improved on decreasing the solut...