Hot deformation behavior and microstructure evolution of GH3536-TiB2 composites fabricated by powder metallurgy

Abstract

The hot deformation behavior and microstructure evolution of GH3536-TiB₂ composites fabricated by powder metallurgy (PM) were examined in the temperature range of 950–1150°C and strain rate range of 0.001–1 s⁻¹. The hot compression stress-strain curves and the constitutive equation were obtained. In addition, the hot processing map was drawn, which indicated that the appropriate hot working window was 950–1050°C/0.001–0.1 s⁻¹ and 1050–1100°C/0.001–0.01 s⁻¹. The microstructure analysis showed that the splitting and spheroidization of M₃B₂ led to a decrease in size and volume fraction at 950–1100°C. At 1150°C, the eutectic microstructure of M₃B₂ + γ was formed due to the dissolution of M₃B₂, which caused macroscopic cracking of the deformed sample. Additionally, the deformation temperature and the strain rate had little effect on the size and volume fraction of M₃B₂. Besides, discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) were found in the deformed microstructure, while the former was dominant. Within the test range of this work, the dynamic recrystallization (DRX) fraction of the deformed composites was high due to the bulging nucleation of numerous interfaces. The DRX grain size increased with increasing deformation temperature or decreasing strain rate. Texture analysis showed that the deformation texture of <101>//compression direction RD existed in the matrix when the deformation temperature was below 1100°C, and the texture type became <001>//RD at 1100°C. Additionally, it was also found that the <001>//RD texture was formed in M₃B₂ under the strain rates of 0.1 and 0.01 s⁻¹.