Study On The Preparation And Microstructure Evolution Of TiB₂ Particles Reinforced Ti₂AlNb-TiB₂ Composite

Ti₂AlNb alloy containing O phase（orthogonal structure）,α₂ phase（close-packed hexagonal structure）and B2/βphase（body-centered cubic structure）has become a research hotspot because of its low density,good specific strength,and good comprehensive mechanical properties.However,the plasticity is poor at room temperature,which limits its large-scale application.The introduction of reinforcing particles is a common means to improve material properties.Titanium-based metal composite materials based on Ti₂AlNb alloy are developed to increase strength,improve room temperature plasticity and friction and wear properties.In this paper,Ti₂AlNb pre-alloyed powder and TiB₂ are used as initial powders,and the spark plasma sintering（SPS）process is used to prepare TiB₂ particle-reinforced Ti₂AlNb-TiB₂ composites.The densification process of Ti₂AlNb-TiB₂ composites in the SPS process is studied.TiB₂ composite material grain size and distribution,phase composition,mechanical properties,and friction and wear properties.Firstly,the Ti₂AlNb-TiB₂ mixed powder was prepared by low-energy mixing powder.The evolution of the morphology of the mixed powder with the weight ratio of TiB₂ was analyzed after low-energy mixing.The Ti₂AlNb-TiB₂ composite material was prepared by the SPS process.The analysis found that as the weight ratio of TiB₂ increases,the grains of the composite material are significantly refined and promote the formation of O phase.Secondly,through room temperature compression test,it is found that 0.5wt.%TiB₂particle reinforced Ti₂AlNb-TiB₂ composite has the best compressive mechanical properties.Its yield strength,compressive strength,and compressive fracture strain are1265.2MPa,2115.6MPa,and 21.4%,respectively,and reveal its room temperature The fracture mechanism is a mixed fracture mechanism of brittle fracture and ductile fracture.The thermal compression test summarizes the evolution of the microstructure of Ti₂AlNb-TiB₂ composites with changes in temperature and strain rate.The reinforcement mechanism of TiB₂ particles reinforced Ti₂AlNb-TiB₂ composites is summarized.Finally,the TiB₂ particle-reinforced Ti₂AlNb-TiB₂ composite material prepared by SPS was used as the initial material.The friction and wear test at room temperature was carried out under 2/4/6N load conditions,and the friction and wear properties of Ti₂AlNb-TiB₂ composite materials were systematically studied under load and TiB₂weight ratio.It is found that the 0.5wt.%TiB₂ particle reinforced Ti₂AlNb-TiB₂ composite has the lowest wear rate,which is 3.66×10^-4mm³·N^-1·m^-1,and it is found that the addition of TiB₂ reinforced particles changes the wear mechanism of the Ti₂AlNb matrix.Formed a mixed wear mechanism with plough wear as the main component and a small amount of adhesive wear.The addition of reinforcing particles TiB₂ reduces the wear rate of Ti₂AlNb matrix.