HEAT-TREATMENT AND MECHANICAL-BEHAVIOR OF SINTERED FE-C-P STEELS

The sintered Fe-C-P alloys are believed to be suitable for structural applications in the as-sintered state only, because of the occurence o f phosphorus grain boundary segregation (PGBS) during heat treatment, which produces brittleness even in quasi- static loading at room tempe rature. This condition reduces the application of these materials, whi ch possess good mechanical properties after sintering. For this reason , the present work is devoted to the study of the segregation phenomen a and the microstructural transformations during heat treatment of sev eral alloys with different phosphorus and carbon contents. The behavio ur of these materials is different, depending on chemical composition. In particular, room temperature tensile brittleness (RTTB) is observe d in high and medium carbon steels only, low carbon steels show an inc rease in mechanical properties. By means of a careful microstructural, fractographic, and secondary ion mass spectroscopy (SIMS) characteriz ation this behaviour was explained, and correlated with the microstruc tural transformations occurring during heat treatment.