Microstructure and Deformability of (Ferrite + Cr_2N) Eutectoid-Structured High Nitrogen Steel

摘要

The austenitic Fe-25Cr-lN mass percent alloy undergoes eutectoid transformation (austenite - > ferrite + Cr_2N) during isothermal heat treatment at 1273K to 873K, resulting in the formation of full eutectoid structure. The T.T.T. diagram of this transformation is expressed by a typical C-curve with a nose temperature at around 1170K. The (ferrite + Cr_2N) eutectoid structure exhibits lamellar structure like pearlite in Fe-C alloy. The lamellar spacing and the block size of the eutectoid structure is decreased with lowering the isothermal heat treatment temperature. Tensile testing revealed that the (ferrite + Cr_2N) eutectoid-structured steel does not possess sufficient ductility although its tensile strength and work hardening rate is very high, similarly as pearlite. The drawability is also required to be improved for the production of high strength stainless wire.