Twin-induced grain boundary engineering in 304 stainless steel

Grain boundary character distributions (GBCD) of type 304 stainless steel cold rolled and then annealed at 1173 K were analyzed by electron back scatter diffraction (EBSD). The results showed that low strain (6-10%) followed by long-time annealing (24-96 h) resulted in a GBCD containing a high fraction of Sigma 9 and Sigma 27 boundaries. The ratio of fraction summation of Sigma 9 and Sigma 27 boundaries (f(Sigma 9+Sigma 27)) to the fraction of Sigma 3 boundaries (f(Sigma 3)), i.e. f(Sigma 9+Sigma 27)/f(Sigma 3), reached 0.14 for the specimen strained by 6% and annealed at 1173 K for 96 h. The connectivity of general high angle grain boundary (HAB) network was interrupted significantly by Sigma 3(n) (n = 1-3) boundaries (special boundaries). However, intermediate strain (20-50%) followed by long-time annealing introduced a GBCD of a much lower fraction of Sigma 9 and Sigma 27 boundaries, the value of f(Sigma 9+Sigma 27)/f(Sigma 3) was only around 0.03 and the connectivity of HAB network was not interrupted basically. Additionally, it was observed that a fair number of clusters consisting of Sigma 3-Sigma 9-Sigma 27 boundaries were developed in the process of low strain followed by long-time annealing (96 h), while the same phenomenon was hardly seen in the process of intermediate strain followed by long-time annealing. (C) 2007 Elsevier B.V. All rights reserved.