Microstructure and Properties of Laser Direct Manufacturing TC4 Alloy Reinforced by B₄C with Different Micro/Nano Particle Ratios

The reinforced TC4 matrix composites are fabricated by adding 3% (mass friction) B₄C particles by the laser direct manufacturing (LDM) technology. The B₄C particles with diameters of 50 μm and 50 nm are mixed with the TC4 particles, and the reinforced TC4 alloys are prepared by LDM technology, with the mass fraction ratios of the micro and nano B₄C particles are 1%∶2%, 1%∶1%, and 2%∶1%. The microstructures and hardness of the reinforced TC4 alloy with different ratios of micro-nano B₄C particles are investigated. The results show that the microstructure of the TC4 alloy is significantly refined after adding B₄C reinforcing phase. The content of B₄C particles with different sizes can affect the crystallinity and grain size of the second phase TiB and TiC. When the content of the nano-B₄C particles is higher, the TiC crystallinity is better, and the TiB phase is embedded in the TC4 crystal as nano-sized particles. When the contents of micro- and nano- B₄C particles are similar, the TC4 matrix has the highest microhardness, so do the the TiB and TiC in the second phase region. Besides, the TiB phase has high crystallinity and large grain size.