Metallographic Methods for Revealing the Multiphase Microstructure of TRIP-Assisted Steels

Classical etching techniques used for the investigation of steel microstructures allow the simultaneous observation of only a restricted number of phases. So far, this limitation has not been too detrimental, because most low-carbon steel grades possess a quite simple microstructure. The recent interest in the so-called TRIP-assisted multiphase steels characterized by complex microstructures requires new developments in metallographic methods. This paper proposes an extension of already known techniques to allow the study of four kinds of TRIP-aided steels. The actual restrictions justifying the development of an improved method are emphasized. In spite of its simplicity, the procedure has the advantage of allowing the simultaneous observation of the four phases that generally compose the microstructure of TRIP-assisted steels; that is, ferrite, bainite, austenite, and martensite. Light and electron microscopy as well as diffraction techniques are used to demonstrate the interest of the method.