Embedding boron into Ti powder for direct laser deposited titanium matrix composite: Microstructure evolution and the role of nano-TiB network structure

The titanium powder embedded with 2.5 vol% TiB was in-situ fabricated by gas atomization and applied for direct laser deposited (DLD) matrix composites. Consistent the network distributed boron-rich zone in composite powder, a three-dimensional (3D) ultrafine structure, consisting of nano-TiB whiskers (TiBw), characterized throughout as-fabricated (DLDed TiB–Ti). Both dendritic equiaxed network, attributed to boron-induced constitutional supercooling subsequent nucleation growth primary ?-Ti, existed composite. addition boron (B) had positive effect on equiaxial transition grain refinement both ?-Ti grains ? grains. Tensile tests showed an enhancement strength compared conventionally homogeneous TiB–Ti composites selective melted CP-Ti. Analyzing mechanism DLDed TiB–Ti, apart from fine-grain strengthening load-bearing TiBw, found have additional contribution improvement strength. Fracture morphology situ tensile observation role structure plastic deformation limitation, crack deflection blunting, which mainly cell size revealed significance structure. • Titanium presented whiskers. microstructure evolution controlled development induced addition. test superior due extra