Grain Boundary Development in Post-hot-deformed Austenitic Stainless Steel

Thermo-mechanical treatment that involves cold deformation and subsequent annealing is given to the material to alter the grain boundary development. In the present work, an attempt has been made to study the grain boundary development in austenitic stainless steel subjected to hot deformation followed by isothermal holding. Axisymmetric compression tests (strain rate of 0.1 s(-1)) have been performed at temperatures of 900 degrees C, 1000 degrees C and 1100 degrees C to develop a true strain of similar to 0.16. The hot compression test was followed by isothermal holding of samples for times of 2 s, 10 s, 100 s and 1000 s. The electron backscatter diffraction study has been made on the thermo-mechanically treated samples. The developed grain boundaries were analyzed for misorientation angle, Sigma 3(n) coincidence site lattice (CSL) boundaries and triple junction (TPJ). The result shows many annealing twins characterized by Sigma 3 CSL boundary. This Sigma 3 CSL boundary breaks the material's grain boundary connectivity and significantly changes the average grain size. At temperatures 900 degrees C and 1000 degrees C, an increase in holding time leads to an increase in the fraction of triple junction J1. On the other hand, at 1100 degrees C, the fraction of J1 is not much affected by the holding time. However, an improvement in the fraction of J3, in comparison to 900 degrees C and 1000 degrees C, has been observed. A maximum value of similar to 0.12 for J2/(1 - J3) has been observed for the sample hot-deformed and held for 10 seconds at 1100 degrees C.