Fabrication mechanism and high-temperature properties of bicontinuous Ti2AlN/TiAl composites: Experimental, DFT, and DL investigations

Abstract

Template forming and pressureless sintering (PS) were used to create porous Ti₂AlN precursors, which served as reinforcements in bicontinuous Ti₂AlN/TiAl composites via reactive melt infiltration (RMI) of the TiAl matrix. Key reactions limiting decomposition and promoting composite formation were systematically studied. The optimal sintering temperature for the porous Ti₂AlN precursors was found to be 1200 °C, while the infiltrated TiAl matrix was processed at 1500 °C. Bicontinuous morphologies, phase compositions, and microstructural distributions of the composites were analyzed using EBSD. A deep learning (DL) model enhanced with image processing techniques classified various phases and microstructures with approximately 80 % accuracy. The interface structure within the composites was characterized by TEM, leading to a density functional theory (DFT) model that discussed adhesion, bonding, and hybridization at the interface. Mechanical properties at room temperature (RT) and elevated temperatures showed compressive strengths of 1354 MPa at RT and 751 MPa at 800 °C, indicating improvements of 13.5 % and 12.6 %, respectively, compared to those of the TiAl matrix under identical conditions. Additionally, intrinsic physical properties of potential phases were estimated alongside developed high-temperature compression models. Insights into high-temperature oxidation mechanisms were derived from analyses on both phase composition and morphology of the oxide layer.