Effect of energy density on porosity, microstructure and mechanical property of Ti65/1.0TiB₂ (wt%) composite fabricated by laser directed energy deposition

The effect of the different energy densities on the porosity, microstructure and mechanical properties of the Ti65/1.0TiB₂ (wt%) composite via the laser directed energy deposition (LDED) is investigated. The defects in the Ti65/1.0TiB₂ (wt%) composite fabricated at low energy density were primarily composed of the poor fusion and gas pores, in which the poor fusion defects disappeared, and the porosity decreased firstly and increased with the increasing of energy density. The TiB whiskers (TiBw) in the Ti65/1.0TiB₂ (wt%) composite fabricated at low energy density clustered along the β grain boundaries, but the TiBw at medium energy density were uniformly distributed along the β grain boundaries, and the TiBw at large energy density were uniformly distributed both along the β grain boundaries and within the β grains. The tension results of the Ti65/1.0TiB₂ (wt%) composite indicated that extreme energy densities adversely affected the room-temperature mechanical properties. The contributions of the different strengthening mechanisms to the yield strengths of the Ti65/1.0TiB₂ (wt%) composite were calculated, which indicated that the grain refinement strengthening effect plays a dominant role. Furthermore, the clustered TiBw with a high aspect ratio and the discontinuous network structure at medium energy density significantly strengthened the Ti65/1.0TiB₂ (wt%) composite.