Investigation of the hot deformation behavior and microstructure evolution of TiB2 +TiAl3/2024Al composite

Abstract

In this study, the hybrid aluminum matrix composite reinforced with TiB2 and TiAl3 particles was fabricated by in situ synthesis. Hot compression tests were performed at a deformation temperature range of 300 − 450 ℃ and strain rates of 0.001 − 1 s−1 on a Gleeble-3500 system to investigate the hot deformation behavior of the fabricated composite. The experimental results show that the flow stress was sensitively dependent on the strain rate and temperature, and the peak stress level increased with the decrease of deformation temperature or the increase of strain rates. A sine-hyperbolic constitutive equation with the hot deformation activation energy of 244.844 kJ/mol was established to describe the flow stress of the composite. Further, the effects of TiB2 and TiAl3 particles on the flow stress levels of the composite under different hot deformation conditions were described by the developed strengthening model. It found that the predicting values of yield strength calculated by the established model agreed well with the experimental data, and the nano-sized TiB2 had a greater contribution to the stress level of the composite compared to the micro-sized TiAl3. Based on the microstructure characterization, dynamic recovery (DRV) was found to be the main flow softening mechanism during hot deformation and the evolution of dynamic recrystallization (DRX) was insufficient. Micro-sized TiAl3 particles and TiB2 particle clusters can promote DRX nucleation and growth of newly formed grains, meanwhile, separated nano-sized TiB2 particles had a pinning effect on the dislocation migration leading to substructure formation, which was in favor of the development of DRV.