Orientation-dependent dynamic recrystallization of super austenitic stainless steels

Abstract

Herein, the hot compression of a super austenitic stainless steel (SASS) containing 7Mo–0.46N–0.02Ce is conducted at different temperatures (900–1200 °C) under a strain rate of 10 s−1. The effect of angle between solidification direction of columnar crystals and loading direction (0°, 30°, 60° and 90°) on microstructural evolution of SASS is studied using OM and EBSD. The results reveal that, at low temperatures of 900 °C and 1000 °C, the dynamic recrystallization (DRX) degree of the 30° and 60° samples is higher than that of the 0° and 90° samples, however, the complete DRX has not occurred. At high temperatures of 1100 °C and 1200 °C, the DRX degree of SASS increases with the decrease of angle between solidification direction of columnar crystals and loading direction. Three kinds of DRX mechanisms for samples with different columnar crystal characteristics are observed, i.e., discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX) and a combination of DDRX + CDRX mechanism. However, under the same deformation conditions, preferentially triggered and dominant DRX mechanisms of samples with different columnar crystal characteristics are different. In the 0° and 90° samples, a large number of high angle grain boundaries (15° ≤ HAGB ≤65°) are developed, and new DRX grains are formed on them. While in the 30° and 60° samples, preferential expansion nucleation and growth of DRX grains take place on original GBs. At 1200 °C, the DRX degree of SASS reaches a maximum of ∼0.97 when the angle between solidification direction of columnar crystals and loading direction is 0°.