Abstract
The hot deformation characteristics of a GH4169 superalloy are investigated at the temperature and strain rate ranges of 1193–1313 K and 0.01–1 s−1, respectively, through Gleeble-3500 simulator. The hot deformed microstructures are analyzed by optical microscopy (OM), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD) technology. The effects of deformation parameters on the features of flow curves and annealing twins are discussed in detail. It is found that the shapes of flow curves are greatly affected by the deformation temperature. Broad peaks appear at low deformation temperatures or high strain rates. In addition, the evolution of annealing twins is significantly sensitive to the deformation degree, temperature, and strain rate. The fraction of annealing twins first decreases and then rises with the added deformation degree. This is because the initial annealing twin characters disappear at the relatively small strains, while the annealing twins rapidly generate with the growth of dynamic recrystallized grains during the subsequent hot deformation. The fraction of annealing twins is relatively high when the deformation temperature is high or the strain rate is low. In addition, the important role of annealing twins on dynamic recrystallization (DRX) behaviors are elucidated. The obvious bulging at initial twin boundaries, and the coherency of annealing twin boundaries with dynamic recrystallized grain boundaries, indicates that annealing twins can motivate the DRX nucleation during the hot deformation.
Highlights
IntroductionThe grain boundary characteristics are notably significant and exceedingly affect both the mechanical and physical properties of a material [1,2]
For polycrystalline materials, the grain boundary characteristics are notably significant and exceedingly affect both the mechanical and physical properties of a material [1,2]
It is generally accepted that the formation of annealing twin is mainly associated with grain boundary migration during the static or dynamic recrystallization [12,13]
Summary
The grain boundary characteristics are notably significant and exceedingly affect both the mechanical and physical properties of a material [1,2]. Grain boundary engineering (GBE) is an effective method to optimize the grain boundary features for improving material properties [4]. Such improvements result from the increased “special boundaries,” which occupy many coincident sites lattice (CSL) adjacent grain boundaries [5,6,7]. It is generally accepted that the formation of annealing twin is mainly associated with grain boundary migration during the static or dynamic recrystallization [12,13]. Mirzadeh et al [14] found that lots of annealing twins generate after the initiation of dynamic recrystallization (DRX)
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