A New Route for Identification of Precipitates on Austenite Grain Boundary in an Nb-V-Ti Microalloyed Steel

The precipitates on austenite grain boundaries in an Nb-V-Ti microalloyed steel have been investigated by transmission electron microscope (TEM) examination of carbon extraction replica. The replica was prepared from specimen etched with saturated picric solution rather than Nital which is conventionally used. Then particles on both grain boundaries and triple point of grain boundaries were clearly observed and identified as (Nb,Ti)(C,N) particles. In case of conventional way, it is difficult to determine the location of particles with respect to austenite grain boundaries. The number of particles observed in new way developed was greatly reduced compared with that found in replica prepared by the conventional way, which may be caused by the dissolution of partial precipitates during the etching with longer time and at higher temperature involved in new way. Despite this, the new way developed provides an effective way to determine the precipitate particles on austenite grain boundaries.