Ti Based Nanocomposites Prepared By High Energy Ball Millng And Selective Laser Melting Behavior

Normally, ceramic particulates reinforced metal matrix nanocomposites could either be added to the composite system exteriorly or be formed through an in-situ reaction manner. It was a rather significant task to homogeneously incorporate nanoparticles into a matrix and avoid nanostructure coarsening. In present work, nanocrystalline/amorphous Ti matrix reinforced with the TiC nanoparticles and in-situ synthesis of TiC/Ti₅Si₃ nanocomposites powders were obtained via high energy ball milling, using the micrometric TiC/Ti and SiC/Ti powders as the raw materials.Meanwhile, the TiC/Ti and TiC/Ti₅Si₃ nanocomposite parts were performed by selective laser melting. With increasing the applied milling time to 15h, the structures of the Ti constituent experienced a change of amorphization due to the large defect concentration induced by severe plastic deformation during milling. The milled powder particles underwent two stages of significant refinement at 10 h and 20 h during high energy ball milling. Finally, ball milled products were typically nanocomposite powder featured by the nanocrystalline/amorphous Ti matrix reinforced with the TiC nanoparticles, it was observed that the nanometer-sized TiC particulates were dispersed uniformly throughout the Ti matrix. The SiC constituent decomposed gradually within 25 h of milling, while the Ti constituent reacted speedily after a relatively short time of 10 h. The structures of the milled TiC/Ti₅Si₃ nanocomposites powders experienced a successive change: pre-refining–coarsening–re-refining on increasing the applied milling time. The refinement of the milled powder particles was based on a layered fracturing mechanism. After milled 25 h, the in situ nanometer-sized TiC particulates were dispersed uniformly within Ti matrix.The TiCx reinforced Ti matrix nanocomposites parts were prepared by selective laser melting. It showed that a high densification level of 95.6% was obtained for SLM-processed parts at a laser linear energy densityηof 1100 J/m. The TiCx reinforcing phase was dispersed uniformly in the Ti matrix, having an ultrafine lamellar nanostructure with an average thickness of 54 nm. The non-equilibrium microscopic pressure tended to prevent TiCx crystals growing up, additionally TiC crystal structure, TiCx reinforcing phase developed with a lamellar nanostructure during laser-induced rapid melting/solidification process. SiC/Ti composite powders after high energy ball milling were undergone selective laser melting, in-situ synthesizing TiC/Ti₅Si₃ composite structure. It showed that a high densification level of 94.6% was obtained for SLM-processed parts at a laser linear energy densityηof 800 J/m. Owing to the Gauss distribution of laser energy density, the local temperature gradient and chemical concentration gradient in the molten pool gave rise to surface tension gradient, producing a significant constitutional supercooling, the in-situ TiC tended to experience a dendrite growth. The formation mechanism of TiC in-situ reinforced Ti₅Si₃ during laser-induced rapid melting/solidification process was discussed.