The microstructure evolution and the effect of grain size, temperature, and TiBw on the deformation mechanism of TiBw/TA15 composites during high temperature deformation

In this paper, the deformation mechanism and microstructure evolution of TiB whisker (TiBw)/TA15 composites during high temperature (HT) rolling and tensile were investigated. The effects of grain size and temperature on the HT mechanical properties, deformation mechanism, and strengthening/softening effects were studied. The influence of temperature on the TiBw fracture mode was analyzed within the range of 600-750 degrees C. The results show that grain boundary slip (GBS) and dislocation motion were more prone to promote the occurrence of discontinuous dynamic recrystallization (DRX) and continuous DRX, respectively. TiBw could withstand higher forces and fractured when the orientation was consistent with the loading direction and at a lower temperature, while it was easier to debond with temperature increasing. TiBw/TA15 composites had Hall-Petch (H-P) and inverse H-P (I-H-P) regions in the range of 4.5-7.0 & mu;m with a critical grain size of 5.8 & mu;m under HT tensile at 600 degrees C and 0.001 s-1. The grain boundary strength decreased with the temperature increased, which caused the transformation of the deformation mechanism and the H-P/I-H-P regions at different temperatures. The deformation was dominated by GBS when the strength of grain boundary was lower than that of intracrystalline. The deformation mechanism transformation temperature of TiBw/TA15 composites was 700 degrees C under HT deformation at 0.001 s-1.