Effects of TiO₂ doping on microstructure and properties of directed laser deposition alumina/aluminum titanate composites

Al₂O₃-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al₂TiO₅ ceramic, different composition ratios of Al₂O₃/Al₂TiO₅ composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO₂ doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al₂O₃ phase is discretely distributed in the continuous aluminum titanate matrix when TiO₂ doping amount between 2 and 30 mol%. With the increase of TiO₂ doping amount, content of Al₂O₃ gradually decreases and its morphology changes from cellular to dendritic. When TiO₂ doping amount reaches 43.9 mol%, the microstructure transforms into fine Al₂TiO₅/Al₆Ti₂O₁₃ eutectic structure. Property test results show that Al₂O₃/Al₂TiO₅ composite ceramics have good comprehensive mechanical properties when TiO₂ doping amount between 2 and 6 mol%.