Anisotropy Of Ti/Al Laminated Composites

Ti/Al laminated composites combines the advantages about high strength,corrosion resistance of Ti,and lightweight of Al,and it is widely used in high-tech fields such as aerospace.Due to the difference in properties between Ti and Al,and the laminated composites was exposed to large plastic deformation during rolling,the microstructure and mechanical properties of the laminated composites are anisotropic.Compared to the homogeneous materials,the anisotropy mechanism of heterogeneous metal laminated composites is more complicated.It is not only related to the deformation of the heterogeneous layers,but also affected by the interface characteristics.The processing and forming performance of Ti/Al laminated composites will be affected due to the anisotropic.Therefore,the anisotropic of Ti/Al laminated composites is urgently needed to be studied.In this paper,aiming at the anisotropy of Ti/Al laminated composites,the microstructure of the interface region along the 0°,45°and 90°directions were observed by optical microscope(OM)and scanning electron microscope(SEM),and the phase composition of the interface layer was analyzed using X-ray diffraction(XRD)and transmission electron microscope(TEM).The results show that the microstructure of the Al layer near the interface region has obvious anisotropy,while the anisotropy of the microstructure of the bonding layer and the Ti layer is not obvious.The bonding layer is basically flat mixed with a small amount of wavy morphology.Only Ti Al₃ intermetallic compound was formed in the bonding layer.The microhardness,tensile properties and bond strength of Ti/Al laminated composites with different orientations were analyzed by Vickers microhardness machine and universal electronic tensile machine.The results show that the microhardness,tensile mechanical properties and bonding strength of the Ti/Al laminated composites have obvious anisotropy.Aiming at the anisotropic of Ti/Al laminated composites under different stress states,the anisotropic of mechanical properties under uniaxial stress state and biaxial stress state was studied by hole tensile test and fracture morphology.The results show that the stress state of the laminated composites during the stretching process is changed due to the presence of circular holes.An additional tensile stress is generated in the direction perpendicular to the tensile axis,so that the laminated composites is in a plane stress state.Although this plane stress state will cause the stress concentration of the composites around the circular hole,it will make the stress field distribution of the composites near the circular hole more uniform,which effectively weakened the anisotropy of the mechanical properties of the composites.Therefore,the anisotropy of the mechanical properties of Ti/Al laminated composites under the plane stress state is significantly lower than that of the unidirectional stress state.Aiming at the effects of different annealing processes on the microstructure,mechanical properties and anisotropy of Ti/Al laminated composites.The effects of annealing temperature on the microstructure and mechanical properties of the composites with different orientations were studied through heat treatment tests at a holding time of 3 hours,annealing temperatures of 410?,450?,490?,530?,and570?.The effects of holding time on the microstructure and mechanical properties of the composites with different orientations were studied through heat treatment tests at a annealing temperatures of 490?and holding time of 1h,3h,5h,7h,and 9h.The results show that the comprehensive mechanical properties of Ti/Al laminated composites are the best when the annealing temperature is 490?and the holding time is 3h.