Surface energy controlled α-γ-α transformation texture and microstructure character study in ULC steels alloyed with Mn and Al

Jai Gautam; Roumen Petrov; Leo Kestens; Elke Leunis

doi:10.1007/s10853-007-2292-4

Surface energy controlled α-γ-α transformation texture and microstructure character study in ULC steels alloyed with Mn and Al

J Mater Sci. 2008;43(11):3969-3975. doi: 10.1007/s10853-007-2292-4. Epub 2008 Jun 1.

Authors

Jai Gautam^{1

2}, Roumen Petrov^{1

2}, Leo Kestens², Elke Leunis³

Affiliations

¹ Department of Metallurgy and Materials Science, Ghent University, Technologiepark 903, Ghent, 9052 Belgium.
² Department of Material Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 Delft, CD The Netherlands.
³ OCAS N.V, Arcelor Mittal Research Industry, Ghent, Belgium.

Abstract

In this article, an ultralow-carbon steel grade alloyed with Mn and Al has been investigated during α-γ-α transformation annealing in vacuum. Typical texture and microstructure has evolved as a monolayer of grains on the outer surface of transformation-annealed sheets. This monolayer consists of <100>//ND and <110>//ND fibre, which is very different from the bulk texture components. The selective driving force is believed to reside in the anisotropy of surface energy at the metal-vapour interface. The grain morphology is very different from the bulk grains. Moreover, 30-40% of the grain boundary interfaces observed in the RD-TD surface sections are tilt incoherent <110> 70.5° boundaries, which are known to exhibit reduced interface energy. Hence, the conclusion can be drawn that the orientation selection of surface grains is strongly controlled by minimization of the interface energy; both metal/vapour and metal/metal interfaces play a roll in this.

Keywords: Coincident Site Lattice Boundary; Grain Morphology; Orientation Imaging Microscopy; Surface Texture; Texture Gradient.