Fabriction And Properties Of Titanium Alloy Matrix Composites Reinforced With Graphene And TiC Particles(TiB Whisters)

Titanium matrix composites（TMCs）have been widely used in aircraft structural materials due to its high strength,good wear resistance and favourable corrosion resistance.In-situ Ti C particles and in-situ Ti B whisters are considered to be ideal reinforcement materials for titanium matrix composites.Graphene（GR）has excellent mechanical properties and has high strengthening efficiency when it is used as reinforcement of titanium matrix composites.In this paper,in-situ multi-reinforced GR-Ti Cp/TC4 composites and GR-Ti Bw/TC4 composites are prepared with nano-Ti C（～50nm）/nano-Ti B₂（～300 nm）and GR as reinforcement material and large size TC4spherical powders as matrix material.The reaction between GR and TC4 is expected to be alleviated by coating Ti C or Ti B₂ on the surface of TC4 to form a barrier.In this paper,the phase structure,microstructure,mechanical properties and toughening mechanism of composites with different content of reinforcing phase were studied.The main research contents and results are as follows:（1）The density of TC4 after sintering at different temperatures is studied.The deformation ratio and microstructure of composites after different thermal deformation treatments（forging upsetting,hot rolling）are studied.The result shows that the density of TC4 reached 98.57%after sintering at 900℃for 5min.The deformation ratio of forging upsetting can merely reach 43.6%,and the deformed microstructure is not obvious.However,the deformation ratio of hot rolling can reach 69.40%,and the microstructure is obviously deformed after hot rolling.（2）The microstructure and properties of GR-Ti Cp/TC4 composites are investigated after sintering at 900℃and hot rolling at 1000℃.The result shows that after sintering at 900℃,the GR-Ti Cp/TC4 with 0.4wt.%GR and 0.05wt.%nano-Ti C shows a quasi-continuous network structure.The microhardness（354.66HV）,tensile strength（1033MPa）and compressive strength（1856MPa）of it are greatly increased by19.5%,20.7%and 6.8%compared with TC4,respectively.After hot rolling at 1000℃,the equiaxial microstructure of sintered GR-Ti Cp/TC4 becomes longer.The tensile strength of hot rolled GR-Ti Cp/TC4 with 0.3wt.%GR（1110MPa）is 12.0%higher than that of sintered samples（991MPa）and he fracture strain of it reaches 12.9%.（3）The microstructure and properties of GR-Ti Bw/TC4 composites are investigated after sintering at 900℃and hot rolling at 1000℃。The result shows that after sintering at 900℃,the GR-Ti Bw/TC4 with 0.4wt.%GR and 0.45wt.%nano-Ti B₂presents a closed continuous network distribution.Compared with TC4,the micro-hardness（348.93MPa）,ultimate tensile strength（1016MPa）and ultimate compsite strength（1821MPa）of GR-Ti Bw/TC4 with 0.3wt.%GR and 0.05wt.%nano-Ti B₂ is increased by 17.7%,27.7%and 8.8%,respectively.The tensile strength of GR-Ti Bw/TC4 with 0.3wt.%GR（1821MPa）is further increased by 11.0%after hot rolling at 1000℃and annealing at 570℃.The fracture strain of it reaches 14%.The strength of the composite material is improved while the plasticity is matained.When the addition of GR is unchanged and simultaneously the addution of Ti C and Ti B₂ are the same,the strength and toughening effect of GR-Ti Bw/TC4 composites is better than that of GR-Ti Cp/TC4 composites.