Electron backscatter diffraction study of orientation gradients at the grain boundaries of a polycrystalline steel sheet deformed along different loading paths

J. W. SIGNORELLI; A. ROATTA; N. DE VINCENTIS; C. SCHWINDT; M. AVALOS; R. BOLMARO; N BOZZOLO

JOURNAL OF APPLIED CRYSTALLOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 50 p. 1179 - 1191

0021-8898

n a polycrystal, the heterogeneity of plastic deformation in a particular grain isgreatly enhanced by adjacent grains that constrain the grain?s local behavior,often imposing orientation gradients. This work aims to characterize andquantify the local orientation gradients near grain boundaries (GBs). Electronbackscatter diffraction (EBSD) measurements were made on a 0.67 mm thickaluminium-killed drawing quality (AKDQ) steel sheet subjected to differentloading paths that are typical of forming operations. A statistical analysis showsthat a considerable fraction of the analyzed GB profiles can be described by anorientation profile with a constant slope near the GB. In order to quantify thisbehavior, as well as the degree of localization, two new parameters, based on thelocal orientation gradient assessed by EBSD, are proposed: BET (boundaryeffective thickness) and GAS (gradient average severity). These parametersshould be considered together, the BET as an effective thickness of the GB zonewhere the orientation gradient takes place and the GAS as a measure of themagnitude or severity of the orientation gradient. Additionally, the GASparameter shows a strong correlation with the accumulated macroscopic strainfor the investigated deformation levels and loading paths, while the BET profileclearly reveals the influence of the GB on the misorientation profiles. Tensionand biaxial stretching results lead to a BET value between 1.5 and 2 mm. Finally,it is shown that the local misorientation in the GB zone, on both sides of the GBline, is disperse and it does not correlate simply with misorientation or even theslip-transfer geometry across the GB. Moreover, the observed average localmisorientation dispersions in GB zones are different for each loading condition