Transformation Textures in Steels.

During the hot rolling of steels, the parent austenite phase develops a crystallographic texture. As a result, the material after transformation (ferrite, martensite, acicular ferrite, or bainite ) also acquires a texture which is related in a precise way to the texture of the parent material. The major component of the transformation texture derived from recrystallized austenite is the {001} , which originates from the cube {100} component of the parent texture. The major components of the texture of pancaked austenite are the Bs {110} and Cu {112} , and these give rise, respectively, to the {332} and {113} components in the transformation product. The Goss {110} , Goss/Bs {011} , Bs/S {168} , S{123} , and S/Cu {236} orientations in the deformed austenite also contribute to the formation of the overall transformation texture. Since more than one parent γ orientation can transform into the same bcc orientation, it is sometimes impossible to determine, unambiguously, the origin of particular transformation texture components in the parent γ texture. The intensity of the overall transformation texture can be increased by the addition of Nb, Ti and V to steel, by giving large reductions during controlled rolling, and by using lower finishing temperatures during processing. Among the transformation texture components, the {332} is the most beneficial from the point of view of achieving good deep drawability and improved strength and toughness. The presence of substitutional solutes such as Mn, Ni, Cr or Mo, finer austenite grain sizes and faster cooling rates during transformation increase the intensity of the {332} component. By contrast, the intensity of the {113} component remains relatively insensitive to the above factors.