Revealing hot deformation behavior of Ti2C-Ti composite and associated dynamic recrystallization mechanism of ceramic matrix

Titanium carbide based composites have attracted much attention owing to their light weight, high elastic modulus, and excellent wear resistance. However, the hot working of these composites has been facing great challenges, especially for the coordinated deformation of brittle phase. Here, soft Ti phase was introduced to improve the thermal deformation ability. In particular, the dynamic recrystallization (DRX) mechanism, crack propagation, and dislocation motion behavior of brittle Ti2C matrix were unveiled in this study. Firstly, a Ti2C-Ti composite was hot compressed at 770-1000 degrees C with strain rates of 0.012-0.0013 s-1. The results showed that the optimal processing temperature was 950 degrees C, at which the microstructure can be refined by DRX behavior without the occurrence of macro instability. In the later softening stage of hot compression, the recrystallized Ti2C grains were formed through both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX). The intergranular Ti phase, which acts as a binder, coordinated the deformation of the Ti2C-Ti composite, and the phase boundaries attracted dislocations on the side of the brittle Ti2C phase. This dislocation motion behavior mitigated stress concentration but inhibited the DRX behavior of the Ti2C phase near the binary phase interfaces. The lamellar Ti precipitates within Ti2C grains facilitated the occurrence of CDRX by promoting the formation of subgrains. The subgrain boundaries were formed when the average distance between dislocation on the dislocation wall was lower than 8.68 nm. Compared with the as-sintered composite, the nanohardness of the Ti2C matrix in the composite deformed at 950 degrees C increased by 17%. The enhanced hardness was mainly attributed to grain boundary and dislocation strengthening effect, as well as the reduction of Ti precipitates.