Preparation,Microstructure And Properties Of NiTi_f/Ti-6Al-4V Laminated Composite

Ti-6Al-4V(TC4)alloy,as a kind of alloy with excellent comprehensive properties,is often used as a matrix in laminated composites,while NiTi alloy is widely used in the field of national defense,such as aerospace,weapons and ships,for its excellent damping properties.In this thesis,Ti-6Al-4V(TC4),1060Al foil and NiTi fiber(grid)are laminated in a certain proportion to prepare functional composites with good comprehensive performance and special damping performance using the method of vacuum hot pressing sintering.However,due to the super elastic property of NiTi fiber,it is not conducive to weave the grid structure,so it is necessary to heat treat NiTi fiber to eliminate its super elasticity.When the quenching process is kept at 750? for 20 minutes,the performance of the fiber will decrease less but it can be woven.Then it needs to be tempered to ensure the recovery of the performance of the fiber.Through the experiment,it can be concluded that the heat preservation in 400-450 ?for a short time will lead to more performance recovery.The microstructure of the laminated composite was observed by OM,SEM,XRD,EDS and other analytical methods.Through the measurrment of the density,elastic modulus,tensile properties and damping properties of laminated composite.It was found that the laminated composite are in good combination without obvious defects such as large cracks and voids.TC4 and Al layer are metallgical bond by diffusion,and Al3Ti phase is mainly formed at the interface.There is a center line of carbides and oxides generated in the diffusion interface near Al layer.Two phases of Al3Ti and Al3Ni are formed around NiTi fiber.Al elments are found at the overlapping region of two NiTi fibers,which indicates that the joints of the fibers are not mechanically combined by pressure.At the same time,there are some oxides around the fiber,which may be related to the oxide layer on the surface of the fiber after heat treatment.Experimental results show that the density of laminated composite is between 3.793-4.426g/cm3.The elastic modulus of the composite is 161.7-168.3GPa.The maximum yield strength of single-layer composite is around 210MPa,and that of multi-layer sample is around 175MPa.The fracture strain of single-layer composite is obviously lower than that of multi-layer composite.The damping property is affected by the subsequent heat treatment and the volume fraction of NiTi fiber.When the volume fraction of NiTi fiber is?4.3%,the composite shows the best damping performance.The damping coefficient is?0.1067kN·s/mm and the loss factor is?0.0702.