The effect of B and Ti–Al intermetallics additions on the microstructure and mechanical properties of hot-pressed B4C

In this work, we studied the microstructure and mechanical properties of hot-pressed B4C, B4C + 5 wt% TiAl, and B4C + B + 5 wt% TiAl. The X-ray diffraction and Raman spectroscopy results showed that the addition of Ti–Al alone did not led to Al doping in B4C, and it did not reduce the degree of amorphization of B4C generated under high shear stresses. In contrast, the co-addition of Ti–Al and B resulted in both B and Al solid solutions in the B4C and effectively mitigated the amorphization of B4C. Electron probe microanalysis (EPMA) and energy dispersive X-ray spectroscopy (EDS) analyses suggested that the co-addition of Ti–Al and B promoted the interdiffusion of lightweight elements such as B, C, Al, Mg, and Si at high temperatures, resulting in a dense body with uniformly distributed second phase. The transmission electron microscopy (TEM) observations of the B4C + B + 5 wt% TiAl sample showed that a nano–core–shell structure with aggregated dislocations in the shells which was generated at TiB2 grains due to the segregation and dissolution-precipitation between TiB2 and B-rich boron carbide. The short-range ordered substitution of B and the disordered doping of Al in B4C led to lattice distortion and expansion, resulting in the formation of high-density defects, including stacking faults and nano-twins, improving the mechanical properties for B4C. The B4C + B + 5 wt% TiAl sample exhibits a combination of fascinating properties, including low density (2.52 g/cm3), high Vickers hardness (35.53 ± 0.83 GPa) and moderate fracture toughness (4.37 ± 0.35 MPa m1/2).