The Effect of Variant Selection on Texture of TWIP/TRIP Steels During Uniaxial Tensile Loading
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TEELS exhibiting twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) are favored due to their unique combination of high stress and elongation. Their industrial processing involves shape giving, during which texture development and phase transformations occur simultaneously (besides other deformation mechanisms). Therefore, a detailed understanding of the underlying mechanisms and their interaction is of great importance. When austenite is mechanically deformed, crystallographic texture develops. When it undergoes transformation, the product phase (ferrite, acicular ferrite, bainite, e martensite, a¢ martensite) is also textured. Since the crystal orientation of the new phase is obtained through phase transformation, the term ‘‘transformation texture’’ was introduced. Transformation texture is governed by the texture of prior austenite, the crystallographic correspondence between austenite and the product phase, and stress. While the first two determine all possible orientations of the new crystals, MARTON BENKE, ADRIENN HLAVACS, and VALERIA MERTINGER are with the Institute of Physical Metallurgy, Metalforming and Nanotechnology, University of Miskolc, MiskolcEgyetemvaros 3515, Hungary. Contact e-mail: [email protected] ERZSEBET NAGY and GABOR KARACS are with the MTA-ME Materials Science Research Group, MiskolcEgyetemvaros 3515, Hungary. Manuscript submitted June 19, 2019. Article published online February 4, 2020 METALLURGICAL AND MATERIALS TRANSACTIONS A
the latter specifies which orientations actually form among all. This is called ‘‘variant selection’’. Miyaji et al.[1] showed that variant selection acts simply due to geometrical non-uniformity even if external load is absent. Since then, the role of variant selection in different steel types has been recognized by many authors.[2–4] To predict the texture of the product phases, models had been established based on the observed {111}c||{011}a¢, h110ic jjh111ia0 orientation relations.[5–9] When it comes to describing the texture of austenite, difficulties arise. First, calculating the austenite texture is rather complicated, since one specific crystal orientation of the product phase can be inherited from multiple parent orientations.[2–4] This problem was resolved with promising results by the method of Tomida et al.[8] which specifies that the orientation relation of a nucleating ferrite and two adjoining austenite grains is fulfilled. Second, the texture of austenite can only be measured if there is a notable amount of retained austenite. In such case, it is possible to directly observe orientation relations between the parent and product phases. The orientation relationship between c and a¢ phases[10] and texture evolution during tensile tests[11,12] or rolling and annealing[13–18] were studied by many authors. In some of these works, conclusions were deduced based on electron backscattered diffraction (EBSD) analysis,[10,11,15] while in others it was done on orientation distribution function (ODF) synthesis.[11–18] Both methods defin
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