Preparation And Microstructure Properties Of Low Dimensional Carbon Reinforced Titanium Matrix Composites

Titanium matrix composites(TMCs)have high specific strength,high specific modulus and excellent high temperature resistance,which meet the strict performance requirements of lightweight and high strength structural parts in the field of aerospace and high-performance vehicles.However,the traditional research idea of TMCS is always devoted to increasing the content of the reinforcing phase and pursuing the uniform distribution of the reinforcing phase.As a result,there is always an inversion relationship between the strength and the plasticity(toughness).In order to solve this problem,in this paper,the two-dimensional material graphene(Gr)with high specific surface area and the one-dimensional carbon nanotubes(CNTs)with high aspect ratio were choosed as reinforcement phases,and high performance low dimensional carbon reinforced titanium matrix composites were successfully prepared by flake powder metallurgy and subsequent hot rolling.By optimizing the process parameters of pre-dispersion,flake ball milling,SPS sintering and rolling,the key problems such as the dispersion of CNTs and Gr in Ti matrix and the interface reaction between CNTs(Gr)and Ti have been successfully solved.The design and preparation of low dimensional carbon reinforced titanium matrix composites are achieved by the following three steps:(1)Preparation of composite powder: the spherical titanium powder were prepared into flak-like powder with higher diameter to thickness ratio by optimized high-energy ball milling process(360 rmp + ball to material ratio 20:1+8h);Then acidified CNTs and Gr with active additive PVA were respectively dispersed by ultrasonic for 8h and 5h,and the dispersed CNTs and Gr solution were mixed by ultrasonic for 3h to obtain the final mixed solution of well dispersed Gr and CNTs.Finally,the Gr and CNTs in the hybrid solution were uniformly dispersed on the surface of flak-like titanium powder by using the optimized low-energy ball milling process(220rmp+ ball-to-material ratio 3:1+4h)to prepare(Gr +CNTs)/Ti layered structural elements.(2)Low temperature and high pressure rapid SPS sintering:the Ti-Gr/CNTs layered structure was successfully prepared by using SPS(600?,250 MPa,15min).(3)Low dimensional carbon reinforced titanium matrix composites rolling: the sintered bulk materials was rolled at 800?with the deformation of 50%,and finally the low dimensional carbon reinforced titanium matrix composites successfully prepared.The microstructure study showed that the Gr and CNTs were uniformly dispersed in low dimensional carbon reinforced titanium matrix composites,and the interface reaction between Gr and CNTs and Ti matrix was effectively controlled under low temperature and high pressure sintering,and only a small number of TiC nanoparticles were formed at the interfaces between reinforced phase and Ti matrix.The mechanical properties show that the microhardness of the sintered Ti-0.08%Gr/CNTs composite is increased by 43.7% to 247.4HV compared with that of the pure Ti,and is 10.8% and 18.5% higher than that of the Ti-0.08%Gr and Ti-0.08% CNTs,respectively.As the mass fraction of CNTs and Gr increased from 0.03% to 0.08%,the compressive strength of low dimensional carbon reinforced titanium matrix composites increased from 1285 MPa to 1426 MPa,increasing by 10.9%.The compressive strength of0.08 wt.% low dimensional carbon reinforced titanium matrix composites was increased by 46.3% compared with that of pure Ti,and the compressive strain is similar to that of pure Ti.After rolling deformation,the yield strength of low dimensional carbon reinforced titanium matrix composites was increased by 37.8% to 686 MPa compared with that of pure Ti plates,and the elongation of low dimensional carbon reinforced titanium matrix composites remained at a high level of 24%.The fracture analysis showed that the tensile fracture had obvious ductile fracture characteristics after rolling deformation.From the results of 3D XRM fracture,it can be seen that the cracks and holes are mostly concentrated near the fracture,and the crack volume decreases gradually with the distance from the fracture.