Process Research On Preparation Of Ti-Al-C Series MAX Ceramics By ISLF/RS

Ti-Al-C MAX phase ceramics(Ti₂AlC and Ti₃AlC₂)have the excellent characteristics of both ceramics and metals,and have a wide range of applications in high-temperature structural materials and other fields.However,due to the freedom of cutting,it is difficult to manufacture complex structures such as internal cavity,crystal lattice,and porous by traditional methods.Laser selective melting(SLM)technology can form a variety of complex shapes by melting the powder layer by layer,providing a new idea for the processing of complex ceramic parts.However,the decomposition characteristic of Ti-Al-C MAX phase ceramics before melting makes it difficult to form SLM through melting-solidification directly.In order to achieve the near-net-shape forming of Ti-Al-C MAX phase ceramics,this paper proposes a new Ti-Al-C MAX phase ceramics preparation process by in-situ selective laser forming combined with reaction sintering based on the reaction synthesis route of Ti-Al-C MAX phase ceramics.The development of phase composition and microstructure during the process was further studied.The powder material system of Al-TiO₂-TiC-CNT was used to prepare Ti₃AlC₂ matrix composites,and the forming experiment with variable ISLF process parameters was carried out to provide a basis for subsequent ISLF forming process research.The study found that reducing the powder compaction rate and increasing the laser input energy were beneficial to promote the in situ reaction,and the distribution of the phases on the sample surface tended to be uniform.The coupling relationship between reaction synthesis mechanism of Ti₃AlC₂ and process characteristics was analyzed with thermodynamic calculation,providing theoretical basis for ISLF/RS process.Based on the difficult-to-formability,powder system of Al-TiO₂-TiC-CNT powder material was adjusted,and Ti-Al-C powder system was used to prepare Ti₂AlC complex structural parts.The phase composition and microstructure of the formed samples were studied by ISLF experiment,and the TiC crystal formation mechanism was revealed then.The study found that increasing the laser energy was conducive to the densification of the sample,while the Kirkendall pores prevented the sample from further increasing the density.There were differences in the morphology of TiC crystals synthesized in situ and ex situ,and growth of dendrite was controlled by laser input energy.The coupling relationship between reaction synthesis mechanism and process characteristics of Ti₂AlC was analyzed with thermodynamic calculation.Based on the ISLF forming experiment of Ti-Al-C powder materials,the effects of ISLF and reaction sintering processes on the phase composition and microstructure of Ti₂AlC samples were studied and summarized.The process correlation between ISLF forming and reaction sintering processes was established,and the synthetic purity of Ti₂AlC block was optimized.It was found that the purity of Ti₂AlC was highest at 87.79 wt.%under the ISLF process with a laser power of 40 W,a scanning speed of 100 mm/s and a sintering temperature of 1300?.