Embedded Grain Rotation and Roping of Stainless Steel

Abstract

The recent application of crystal plasticity calculations to electron backscatter diffraction (EBSD) data from ferritic stainless steel sheet has confirmed the presence of grain clusters parallel to the rolling direction (RD) with similar deformation tendencies. The results of these simulations provide strong support for the Takechi model of roping. The remaining question that has not yet been adequately addressed is how the deformation tendencies of grains/grain clusters are affected by being embedded within a three-dimensional medium. In this article, the behavior of individual grain orientations when embedded within media of differing crystallographic orientations is explored within the framework of a viscoplastic self-consistent (VPSC) model. It is shown that the tendency for out-of-plane shear exhibited by some grain orientations persists, even when the grains are embedded within a matrix that has very different deformation tendencies. This is further extended to examine the influence of the orientation of grain clusters in relation to the roping phenomenon.

Quantification of the Morphological Signature of Roping Based on Multiscale Analysis and Autocorrelation Function Description

“…The terms ‘roping’ and ‘ridging’ refer to the surface appearance of the material that shows rope-like features parallel to the prior rolling direction and distributed along the transverse direction. This phenomenon was observed in ferritic stainless steels [ 1 , 2 ] as well as aluminum alloys [ 3 , 4 ]. Both materials are often used for exterior applications whose surface appearance is important (e.g., automotive body applications).…”

Accounting for local interactions in the prediction of roping of ferritic stainless steel sheets

“…Grains having a strong shearing tendency were embedded within a matrix having either a strong opposite shearing tendency or no shearing tendency. From these simulations it was shown that the tendency for shearing in orientations such as {1 1 1} 1 1 0 was far stronger than the tendency for no shearing in grains having orientations such as {1 1 1} 1 1 2 , this result being explained by the difference in the slope of Taylor factor with respect to shear component of the deformation gradient [13]. These results indicated that the grains having no net tendency for shearing would shear if placed adjacent to grains having a strong shearing tendency, thereby increasing the number of grains contributing to the net shearing behaviour.…”

“…It is known empirically, however, that the microstructure through the sheet thickness has a significant effect on the characteristics of roping. In an attempt to specifically look at the importance of local environment on the tendency for individual grains to shear, Sinclair [13] used the VPSC code with idealized microstructures to study the deformation behaviour of individual grains embedded within different media. Grains having a strong shearing tendency were embedded within a matrix having either a strong opposite shearing tendency or no shearing tendency.…”

“…Following on the work of Sinclair [13], this work seeks to examine the role of local environment of individual grains on the tendency for shearing by examining the information contained in the RD plane (plane containing the ND and TD) of the sheet as opposed to the more commonly examined ND plane. EBSD maps measured on this plane are used for input to crystal plasticity simulations.…”

Influence of the Cold Rolling and Annealing Sequence on the Ridging Behaviour of Ti‐Stabilized 18% Cr Ferritic Stainless Steel

“…Such bands are believed to originate from the as‐cast columnar grains with {001}〈uv0〉 orientations, which persist even after numerous processing steps 4–6. There is now a general consensus that the out‐of‐plane shear rate model put forward by Takechi et al 8 and later validated by others 5, 7, 9, 10 is the most likely mechanism of ridging in the presence of a banded orientation distribution.…”