Strength–ductility trade-off in TiB-TC4 composites with a pseudo core–shell structure

Heterogeneous structure is practical to improve the strain hardening abilities of materials due to the effect of hetero-deformation induced hardening, especially of composites. In this study, a series of TiB/TC4 composites with a pseudo core–shell structure of bimodal grain distribution were fabricated via a two-step ball-milling and spark plasma sintering. The synthesized TiB/TC4 composites have a structure of coarse lamella α-Ti grains of average 23.6 μm in diameter surrounded by fine α-Ti lamella grains of average 4.2 μm, with TiB distributed on the primary TC4 surface areas. TiB/TC4 composites with 0.4 wt% TiB₂ exhibited the best comprehensive mechanical properties with an ultimate tensile strength of 1161.95 MPa (a 35.1% increase compared with that of pure TC4) and an elongation of 7.57%. In conclusion, the pseudo core–shell structure improved the strength by improving the strain-hardening abilities, achieved by the coordinated deformation between coarse grains and fine grains.