Formation of core-shell structure in W-added B4C-based composites

Abstract B4C-TiB2-SiC composites with W addition were successfully prepared by spark plasma sintering with B4C, TiB2, SiC, and W as raw materials. The XRD results indicate that the main phases of the composites are B4C, TiB2, SiC, and W2B5. A large number of core-shell structures were observed in the composites with the introduction of W. It is determined that the core is the TiB2 phase and the shell is a (Ti, W) B2 solid solution by EDS, EBSD, and TEM characterization methods. The core-shell structure is conducive to the deflection of cracks, thereby improving the fracture toughness of the composites. As a result, with the increase of W addition from 0 to 5 vol%, the fracture toughness of composites increased from 3.96±0.25 to 5.14±0.23 MPa·m1/2, the Vickers hardness improved from 20.24±0.22 to 28.35±0.22 GPa.