Grain boundary engineering in a thermo-mechanically processed Nb-stabilized austenitic stainless steel

• Published in: IOP conference series. Materials Science and Engineering Vol. 82; no. 1; pp. 12113 - 12116
• Main Authors: Yunquera, A, Jorge-Badiola, D, Gutiérrez, I, Iza-Mendia, A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 24.04.2015
• Subjects: Annealing; Austenitic stainless steels; Boundaries; Cold working; Electron backscatter diffraction; Grain boundaries; Grain boundary migration; High temperature; Optimization; Recrystallization; Stainless steel; Strain annealing; Twinning
• ISSN: 1757-8981; 1757-899X; 1757-899X
• DOI: 10.1088/1757-899X/82/1/012113

Three different thermo-mechanical strategies-annealing, strain recrystallization and strain annealing-were applied to a Nb-stabilized 304H austenitic stainless steel in order to study their effects on grain boundary character distribution (GBCD). An Electron Backscatter Diffraction (EBSD) analysis revealed specific combinations of cold reduction-temperature-time that favor annealing twinning. A uniform increase in microstructural size and special boundaries (particularly for Σ3, Σ9 and Σ27 boundaries) was achieved under strain annealing conditions (low cold reductions) and long times at high temperatures (≥ 990°C). These conditions provide a high fraction of special boundaries (about 80%), which replace the random grain boundary network and thus optimize the GBCD. The profuse presence of Σ3n boundaries is attributed to the geometric interaction of twin-related variants during grain boundary migration. In addition to all this, precipitation takes place at the temperature range where optimum GBCD is achieved. The significance of precipitation in the different strategies was also tackled.