Effects of deformation conditions on the microstructure and substructure evolution of TiBw/Ti60 composite with network structure

摘要

The microstructure evolution of TiBw/Ti60 composite with network structure has been investigated during isothermal compression in the temperature range of 900-1100 ℃ and strain rate range of 0.001-1 s~(-1). Substructure evolution and deformation mechanism have been further investigated by electron backscatter diffraction (EBSD). In α+β phase region, the degree of flow softening decreases with the increase of temperatures and strain rates. At 900 ℃, flow softening is attributed to the dynamic recovery (DRV). At 950 ℃, flow softening is mainly attributed to globularization of primary α (α_p) phase with the continuous dynamic recrystallization mechanism (CDRX). With decreasing strain rates, low angle grain boundaries (LAGBs) in α_p phase were decreased and transformed into high angle grain boundaries (HAGBs), which can result in globularization of α_p phase. In single β phase region, the prior β grain boundaries are reconstructed based on the misorientation criterion between α_s-colonies using the EBSD data. Moreover, DRV, DRX and the growth of β grains occurred at low strain rates. In addition, TiBw played an important role on the microstructure evolution of matrix. At high strain rates, TiBw were seriously broken and TiBw were surrounded by lots of LAGBs. At low strain rate, DRX of p phase and globularization of a phase occurred prior near TiBw region due to providing the nucleation site for DRX and strain accumulation respectively.