Thermal deformation behavior and microstructure evolution of GH4169 superalloy under the shear-compression deformation conditions

Abstract

The shear-compression deformation of GH4169 superalloy at 1000–1200 °C and 0.01–1 s−1 was investigated by physical and numerical simulation based on a specific shear-compression sample (SCS). OM, EBSD, and TEM analysis revealed the three typical regions in SCS. Dynamic recrystallization (DRX) preferred to occur in the slot region due to the strain concentration, where the Mises equivalent strain was about 4–6 times higher than the pre-set ones. Mixed grains were observed in the transition region because of insufficient deformation. In contrast, equiaxial grains were preserved in the cylindrical region with negligible deformation. Experimental stress decreased with the increase of temperature and decrease of strain rate. The maximum stress was 180 MPa, which was only 30% of that under single compression deformation. Furthermore, four DRX mechanisms were observed in GH4169. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) were the dominant and auxiliary mechanisms, respectively. Twinning dynamic recrystallization (TDRX) occurred in the annealing twins with a fast nucleation rate, and the intersected nano-twins provided favorable nucleation sites for DRX. Lastly, secondary dynamic recrystallization (SDRX) with unique nucleation mechanism of triangularly intersecting subgrain boundaries emerged in SCS, which nucleated in the DRX grains and further refined the microstructure of GH4169.