Effects of recrystallization and grain growth on the formation of annealing twin in the 304 stainless steel

Abstract

The objective of this thesis was to increase the fraction of structurally ordered boundary (Coincidence-site-lattice boundary, CSLB) in 304 stainless steel in an attempt to improve its intergranular corrosion properties. Methods used to increase the CSLB fraction were based on the thermomechanical processing including recrystallization, one-step strain annealing, and iterative strain annealing. The Electron Back-scattering Diffraction Pattern (EBSP) in scanning electron microscope (SEM) was employed to characterize type and fraction of grain boundaries. The results show that recrystallization and one-step strain annealing processes do not increase the fraction of CSLB sufficiently to resist intergranular corrosion. Meanwhile, iterative strain annealing was found to increase the CSLB fraction up to 54% in the specimen recrystallized at 850 ํC for 2 hr, then underwent 3 sequential strain annealing steps consisting 3% reduction in thickness and heat treated at 950 ํC for 10 min.