Laser ignition chemical synthesis of bulk Al2O3-TiB2 composites for impact resistance application

The increasing demand for advanced materials has prompted the exploration of energy-efficient processes for near-net shape manufacturing. Laser ignition chemical synthesis (LIChemS) is a novel technology for rapid and cost-effective synthesis of refractory materials. Using a 976 nm quasi-CW diode laser, we manufactured Al 2 O 3 -TiB 2 composites in situ from aluminum, TiO 2 , and B 2 O 3 . Leveraging low-power laser processing and an exotherm-driven mechanism, which involves keyhole formation, metal vapour ionisation, and Marangoni convection, LIChemS generated plasma for propagating the reaction across the bulk, for laser intensity of 1.13 W/mm 2 . The adiabatic temperature and activation energy of LIChemS were calculated as 2643 K and 11.6 kJ/mol respectively. A Newtonian cooling model predicted crack generation within the composites for a differential temperature of 349 K between the centre and edges. We propose a new reaction mechanism yielding high-purity composites, displaying only traces of Ti 2 O 3 . The composites exhibited skeletal and bulk densities of 4010 kg/m 3 (96 %) and 3830 kg/m 3 (92 %) respectively, fracture toughness of 5.8 MPa m 1 / 2 , and Vickers microhardness of 18.14 ± 0.49 GPa. The optimum Al 2 O 3 -TiB 2 composite demonstrated 15 % greater compressive strength than monolithic alumina and withstood 174 N before fracturing. An analytical model combining Hertzian contact mechanics with impact mechanics correlated the ball-drop heights during impact testing to the defect sizes within the composites. The composites presented a surface roughness of 14.9 μm and fine dispersion of TiB 2 and Ti 2 O 3 nanoparticles within the alumina matrix. The results herein suggest great scalability opportunities for LIChemS in manufacturing customised, high purity, energy demanding materials.