TiN/γ-Fe interface orientation relationship and formation mechanism of TiN precipitates in Mn18Cr2 steel

A Mn18Cr2 steel containing TiN precipitates was fabricated by vacuum induction melting. The morphology of TiN precipitates and the interface orientation relationship between TiN and gamma-Fe were characterized by means of SEM, TEM and SAED, and the formation mechanism of TiN precipitates in Mn18Cr2 steel was clarified. Results show that the TiN precipitates are more likely to exhibit a cubic-shaped morphology and form both within the grain and at the grain boundary of gamma-Fe. The interface orientation relationship between TiN and gamma-Fe is determined as follows: (100)(TiN)//(1 (1) over bar1)(gamma-Fe), [0 (1) over bar1](TiN)//[(1) over bar 12](gamma-Fe). Because of the smallest interfacial misfit, the secondary close-packed lane {100} of TiN preferentially combines with the close-packed plane {111} of gamma-Fe during the precipitation in order to minimize the interface energy. After nucleation, the TiN precipitates exhibit cubic appearance due to the fact that the TiN has a FCC structure with rock salt type structure. This study provides reference for the material design of the austenitic high-manganese steels with excellent yield strength.

Automated summary

This study revealed the formation mechanism of TiN precipitates in Mn18Cr2 steel and the orientation relationship between TiN and gamma-Fe, providing important reference for the material design of austenitic high-manganese steels with excellent yield strength.