Microstructure and mechanical properties of bimodal heterogeneous TiB_w/TC4 composites with high strength and toughness

Heterostructure has been improved to improve comprehensive mechanical performance of materials. In this work, bimodal heterogeneous TiB_w/TC4 composites with fine-grained (FG) TC4 as the main matrix plus different contents of relatively dispersed distribution coarse-grained (CG) TC4 zone were successfully prepared by two-step low-energy ball milling and vacuum hot-pressing sintering (HPS). TiB_w is dispersed in the FG zone and distributed in a near-circular shape around the CG boundaries. At the same time, compared with traditional homogeneous composite (TMC0), the introduction of CG can also refine matrix grains, which contributes to the improvement of comprehensive mechanical properties. The optimized heterogeneous composite has a 10 wt% of CG, whose tensile strength is 1129.5 ± 8.2 MPa and elongation is 4.3 ± 0.3 %. Compared with TC4 matrix, it has increased by 17.2 % and 38.7 %, respectively. Compared with TMC0, the average tensile strength did not decrease while the elongation increased by 377.8 %. The fracture toughness is 37.9 ± 1.7 MPa· m, which is 67.0 % higher than that of TMC0. Back stress strengthening, plastic deformation in the CG zone, and failure of TiB_w are the key in delaying the cracking of heterogeneous composites and improve the mechanical properties.