Microstructure and mechanical properties of B4C-TA15 composites prepared by laser powder deposition

GAO Wei; LU Dingding; LIU Yang; HUANG Hao; YU Jie; WANG Lijie; XIONG Wenwen; WANG Huaizhi; DING Xuefeng

doi:10.13732/j.issn.1008-5548.2026.02.008

Abstract：Objective Titanium alloys are widely used in critical load-bearing components and engine structures in aerospace due to their excellent mechanical properties,such as high specific strength,good creep resistance,and wear resistance.With the development of aviation and military industries,the new generation of supersonic aircraft has attracted significant attention due to its increased flight speeds.The acceleration process of the aircraft imposes stringent requirements on both engine thrust and thrust-to-weight ratios,inevitably resulting in a rise in the engines' operating temperature.Therefore,developing titanium alloys with exceptional high-temperature resistance is crucial to meet the needs of high-performance aero-engines.The incorporation of hard strengthen-ing phases,such as B4C,TiC,SiC,TiB,and Ti5Si3,which possess high strength,superior high-temperature resistance,and good wear resistance,is one of the effective approaches to enhance the high-temperature mechanical properties of titanium alloys.Laser powder deposition(LPD)is a new type of metal additive manufacturing technology,characterized by its ability to directly prepare complex metal components with excellent mechanical properties and high density.In this process,metal parts are manu-factured layer by layer based on a solid three-dimensional model.The metal powder is initially melted by a high-energy density laser onto a metal substrate,forming a molten pool,which is then cooled and solidified.This process is repeated with preset mod-els and parameters until a complete three-dimensional component is formed.LPD has introduced a new technique for the prepara-tion and forming of metal parts,such as titanium matrix composites,addressing challenges in manufacturing difficult-to-produce metal parts for aerospace and other fields.However,at present,the microstructure and high-temperature strengthening mecha-nisms of titanium matrix composites prepared by LPD still remain unclear.Therefore,it is necessary to explore how the reinforc-ing phases influence the microstructure and high-temperature mechanical properties of these composites. Methods B4C-TA15 composites prepared by LPD were studied and compared with TA 15 alloys to clarify the complex relation-ship between microstructure and high-temperature mechanical properties.Firstly,B4C-TA15 composites with suitable shapes were prepared using a mixture of B4C and TA 15 powders under appropriate parameters through the LPD process.Subsequently,the morphology,grain structure,and interface bonding of the composites were assessed using microstructure characterization methods to explore their microstructural evolution.The tensile properties of the experimental samples were tested at 600 ℃ to evaluate their high-temperature performance.Finally,the strengthening mechanisms of the composites prepared by LPD were investigated by establishing correlations between microstructure and high-temperature mechanical properties. Results and Discussion According to the experimental results,a composite material with TiB and TiC reinforcing phases non-uniformly distributed within the TA 15 matrix was successfully synthesized through low-energy ball milling and the LPD process,with a B4C content of 3％.The incorporation of TiB and TiC hard reinforcing phases in the B4C-TA15 composites significantly changed the grain morphology and size of the titanium matrix,transitioning from slender,plate-like grains to near-equiaxial,square grains.The grain size of the B4C-TA15 composites was significantly reduced compared to that of the TA 15 alloys.Addi-tionally,the TiB and TiC phases were well bonded to the TA15 matrix,creating a clean and smooth bonding interface,showing a good strengthening effect.The B4C-TA15 composites demonstrated excellent high-temperature strength while maintaining good toughness and plasticity.Specifically,the tensile strength of the TA15 titanium alloy at 600 ℃ was measured at 653 MPa,whereas the B4C-TA15 composite was 803 MPa at the same temperature,marking a 22.97％increase compared to the TA 15 alloy under the same tensile conditions. Conclusion The TiB and TiC reinforcements in the B4C-TA15 composites exhibit a non-uniform distribution,resulting in a het-erogeneous structure characterized by regions with rich and poor reinforcements.In regions with poor reinforcements,the disloca-tion slip generated by the matrix is effectively impeded by the regions with rich reinforcing phases,leading to a significant"dislo-cation pinning"effect.This effect induces stress concentration,thereby enhancing the material's strength.The primary high-tem-perature strengthening mechanisms of B4C-TA15 include bearing and dislocation strengthening of in-situ formed TiB and TiC,along with fine grain strengthening facilitated by reinforcing phases.In addition,TiB and TiC reinforcements increase the service temperature of the material,inhibiting softening of the titanium matrix at high temperatures,and significantly improving the high-temperature mechanical properties of the composites.