Two-step strengthening: Assist in enhancing the strength and maintaining plasticity of TiBw/TC4 composites

The long-term demand for high strength and high toughness drives the development of titanium matrix composites (TMCs). In this work, the room temperature mechanical properties of TiB_w/TC4 composites prepared by two-step low-energy ball milling and vacuum hot-pressing sintering (HPS) were successfully improved by two-step strengthening strategy. The synergistic optimization of strength and plasticity was achieved by using the grain bimodal heterogeneous design combined with the quenching and aging heat treatment process. The tensile strength and elongation of the as-HPSed composite with 10 wt% coarse-grained TC4 (CG) are 1129 MPa and 4.3 %, respectively, which are 17.2 % and 38.7 % higher than those of the TC4 matrix. After 910 ℃/1h quenching and 500 ℃/6h aging treatment, the composite exhibits more excellent comprehensive properties. The tensile strength is increased to 1202.5 MPa and the elongation still keeps to be 4.1 %. At the same time, the fracture toughness is 31.2 MPa $\sqrt{\text{m}}$, which is 37.4 % higher than that of the untreated homogeneous composite. The strengthening mechanism analysis reveals that the synergistic effect of grain boundary strengthening, load transfer strengthening and dislocation strengthening is the key to strength improvement.