Towards understanding the development of grain boundary clusters in austenitic stainless steel

The development of global microstructure characteristics has been compared to the local distribution and extent of Σ3 and Σ3 n (1≤ n ≤3) grain boundary clusters as a function of thermo-mechanical processing in Type 304 stainless steel. A cold reduction of 5% produced GBE modified microstructures on annealing at 1050°C, containing almost one order of magnitude longer maximum cluster lengths than the corresponding annealing treatments for a reduction of 15%. Differences in the development of the distributions of cluster length scales were observed between the thermo-mechanical treatments. A re-conversion of the longest cluster obtained after GBE processing was observed with long annealing times. The local distribution of Σ3 n boundary clusters was assessed, and regions with a low density of clusters are indicative of the onset of GBE conversion of microstructure.