Anisotropy of Retained Austenite Stability during Transformation to Martensite in a TRIP-Assisted Steel Esmaeil Emadoddin,  Abbas Akbarzadeh, Roumen Petrov, and Lie Zhao Retained austenite as a key constituent in final microstructure plays an important role in TRansformation Induced Plasticity (TRIP) steels. The volume fraction, carbon concentration, size, and morphology of this phase are the well-known parameters which effects on the rate of transformation of retained austenite to martensite and the properties of steel, are studied by many researchers. Of the transformation of retained austenite to martensite under strain in a TRIP steel is studied in this paper. The experimental results show that the transformation rate of retained, austenite with similar characteristics, to martensite in differently processed TRIP steel samples, exhibits an anisotropic behavior. This phenomenon implies a kind of variant selection of martensitic reaction of retained austenite under strain and is explained by ferrite texture developed in steel. 1. Introduction Nowadays, many industrial innovations are focused on use of high performance materials. TRansformation Induced Plasticity (TRIP)-assisted steels are appropriate example for such a material. They are class of low alloy steels with improved strain and ductility that are developed in new sheet industrial applications. [1–4] The multiphase TRIP assisted steels contain ferrite, bainite/martensite, and retained austenite. Transformation of retained austenite to martensite by straining achieves exceptional properties such as high strength, good ductility, better stretching formability, and shock absorption. [1,5–9] The amount, distribution, and transformation charac- teristics of retained austenite directly affect the TRIP behavior. [10,11] The role of retained austenite character- istics on TRIP behavior has been extensively studied [1,2] and the available results are sufficient to predict their influence on the steels properties. In this way, processing parameters such as chemical composition, thermomech- anical conditions of production, intercritical annealing temperature of cold rolled sheets, bainitic treatment con- ditions have been widely studied to produce TRIP steel sheets for industrial applications. [12–18] There seems to be lack of studies on textural depend- ence of the martensitic transformation of retained austen- ite in TRIP steels. [19–22] Hence, in the present paper, anisotropic behavior of martensitic transformation of retained austenite is investigated in a recently developed industrial Al-contain TRIP-assisted steel. This behavior is referred as the different amount of martensitic transform- ation of retained austenite when load was applied at different direction of TRIP steel sheet. The variations of strain-induced martensite are evaluated along two direc- tions in samples experimentally designed with similar specifications of retained austenite and different ferrite textures which were developed by different thermo- mechanical processing. 2. Experimental Work The chemical composition of the steel used in this study is shown in Table 1. Different hot rolling schedules are employed to process hot bands with thickness of 2.7 mm. Table 2 shows the finish hot rolling temperature and cooling conditions of samples. For simulation of coiling [  ] Dr. E. Emadoddin Faculty of Materials and Engineering, Semnan University, Semnan, Iran Email: emadoddin@semnan.ac.ir A. Akbarzadeh Faculty of Material Science and Engineering, Sharif University of Technology, Azadi Ave., Tehran, Iran R. Petrov Dept. of Metallurgy and Materials Science, Ghent University, Technologiepark 903, Ghent, Belgium L. Zhao Dept. of Materials Science and Engineering, Delft University of Technology (TU Delft), Mekelweg 2, Delft, the Netherlands L. Zhao Materials Innovation Institute, Mekelweg 2, 2628 CD Delft, the Netherlands DOI: 10.1002/srin.201200197 www.steel-research.de ß 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim steel research int. 84 (2013) No. 3 297 FULL PAPER