FURTHER INVESTIGATIONS ON MARTENSITES IN FE-0.5WT-PERCENT-C AND FE-0.5WT-PERCENT-C-24WT-PERCENT NI MELT SPUN RIBBONS

The types of martensites occurring in Fe-C and Fe-Ni-C melt spun ribbons in the as-solidified and after heat treatment conditions has been investigated using transmission electron microscopy. It has been found that melt spinning of Fe-0. 5 wt% C induces a dislocated martensitic structure at room temperature even for grains as fine as 3 mu m. The martensite laths are separated by thin layers of retained austenite. Some of the martensite laths exhibit a twin relation. The dislocations within the laths are mainly screw. The counterpart alloy, Fe-0. 5 wt% C-24 wt% Ni exhibits 100% austenite under similar conditions. Increasing the austenite grain size upon annealing enhances martensitic transformation. The present work is concentrated on the details of butterfly martensite obtained in these ribbons.