Formation mechanism and application potential of Σ1 boundary in grain boundary engineering of high nitrogen austenitic stainless steel

Sigma 3 boundaries improve the intergranular corrosion resistance of high nitrogen austenitic stainless steels. However, the regeneration of these boundaries is, unfortunately, accompanied by significant grain coarsening. 18Mn18Cr0.5N and 18Mn18Cr0.6N steels were thermo-mechanically processed and the corresponding microstructures were evaluated. Formation mechanisms were proposed for Sigma 1 boundaries in different R-Sigma 3-Sigma 1 -type junctions. These boundaries formed during grain growth accompanying Sigma 3 formation and reaction. After 30% cold tension and cyclic heating between 500 degrees C and 1100 degrees C, numerous Sigma 1 boundaries were formed and disrupted the high angle grain boundary network efficiently. Moreover, a small grain size was maintained. Sigma 1 boundaries have significant application potential in grain boundary engineering. (C) 2019 Elsevier B.V. All rights reserved.