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

摘要

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 γ-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 γ-Fe.The interface orientation relationship between TiN and γ-Fe is determined as follows:（100）TiN//■γ-Fe,■TiN//■γ-Fe.Because of the smallest interfacialmisfit,the secondary close-packed lane {100} of TiN preferentially combines with the close-packed plane {111} of γ-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.