Achieving synergistic enhancement of strength and plasticity of (TiC+Ti5Si3)/TC4 composites by dual-scale near-network structure design

To solve the problem of low plasticity in homogeneous particle-reinforced composites,micro-nano dual-scale near-network (TiC + Ti5Si3)/TC4 composites were prepared by in-situ melting-casting technology. The microstructural evolution, strengthening and friction mechanisms of micro-nanoscale composites were systematically investigated. The results showed that with the increase of the reinforced phase content, the morphology of micron-sized TiC changes significantly from the initial short plume to granular gradually, and the nano-sized Ti5Si3 particles change from small particles to ellipsoidal gradually precipitated at the beta-Ti and alpha/beta interfaces. The (3 vol%TiC+3 vol%Ti5Si3)/TC4 composites (TMCs-2) exhibits excellent mechanical properties with compressive strength of 1774 MPa, plasticity of 24.5 % and hardness of 52.8 HRC. The increase in strength of the composites is attributed to the synergistic effect of matrix (fine grain strengthening, solid solution strengthening) and particle strengthening. The special structural design can effectively hinder the propagation of cracks, lead to crack deflection and passivation, and delay the fracture of composites. The addition of TiC and Ti5Si3 reinforced phases can improve the shear resistance of the surface and subsurface layers of the composites, which can inhibit the emergence of microcracks during sliding wear process, and the wear resistance is significantly improved. At the same time, the micro-nano structure design effectively avoided stress localization and significantly improved the deformation coordination ability of the composites.