Study Of Roll-bonding Process As Well As Microstructure And Properties Of Ti/Al/Mg Laminated Plates

Laminated metal plates in the aviation,aerospace and automotive industries have great potential applications.It is necessary to study the combination effect,microscopic combination mechanism and their influence on mechanical properties.In the present study,Ti-6Al-4V/Al 3003/Ti-6Al-4V,Al 6061/Ti-6Al-4V/Al 6061 and Ti-6Al-4V/Al 6061/ AZ31 B laminated metal plates were successfully fabricated by hot-rolling using Ti,Al and Mg alloy sheets.The effects of hot-rolling process on the microstructures and mechanical properties of the composites,and the plastic deformation mechanism,combination effect and properties of the composite sheets were studied.For the Ti/Al/Ti laminated plates,the development of microstructure through the thickness of Al layer was inhomogeneous.The deformation of the Al/Ti interface is significantly higher than that of the Al layer.The inhomogeneity of deformation through the thickness of Al layer can be attributed to the effect of the uncoordinated deformation between Al and Ti layers and the inhomogeneity of initial microstructure.For the Ti/Al/Ti laminated plates,the UTS and YS increased with increasing rolling temperature,and the EL increased slightly.The UTS and YS increased significantly with increasing rolling reduction,whereas the EL decreased.The bonding strength increased with increasing rolling temperature and reduction.The enhancement mechanism of the tensile strength of the composite plate is related to the restraint of the necking and deformation of the composite material.For the Al/Ti/Al laminated plates,the number of high-angle boundaries and the misorientation angle across low-angle boundaries increased as the thickness position moved towards the surface of Al layer from the interface of Al/Ti.The texture at the surface of Al layer was characterized by the r-cube shear texture and remaining C? and S? textures,while the texture of Al layer near the interface consisted of the {011} <322> orientation and remaining cube orientation.This inhomogeneity of microstructure can be attributed to the effect of the friction between the roller and sheet surface as well as the uncoordinated deformation between Al and Ti layers.With the increase of the rolling reduction,the inhomogeneity of deformation distribution through the thickness of the Al layer increased,the intensity of the r-cube increasd while the residual C' component increased firstly and then decreased,the intensity of S' component decreased.For the laminated composites fabricated with rolling reductions of 27% and 38%,the yield and tensile strength increased to a maximum value at about 400°C and then decreased with increasing rolling temperature.The laminated composites fabricated with a 45% reduction possessed lower strength in the temperature range from 400°C to 450°C than those with a 38% reduction due to the fracture of Ti layer.The microstructure development through the thickness of Al and Mg layers in Ti/Al/Mg laminated plates was inhomogeneous.The deformation near the Al/Mg interface was larger than that of the Al layer,and the initial grains in the region near the interface of Al/Ti were markedly fragmented into equiaxed fine grains.The distribution of the aluminum layer texture in the thickness direction corresponded to that of the microstructure.The texture near the Al/Mg interface and the aluminum center layer contained ?-fiber,Goss and residual cube orientation.While the texture near the Al/Ti interface was mainly composed by r-cube and ?-fiber texture.The grain size of Mg increased gradually from the surface of Mg layer to the Mg/Al interface.The inhomogeneity of microstructure in Al layer was due to the uncoordinated deformation between Al and Ti layers,while the inhomogeneity of microstructure in Mg layer was attributed to the effect of the friction between the roll and sheet surface.The UTS and YS of the laminated composites fabricated at 450°C increased with increasing rolling reduction,while the EL decreased.For the laminated composites fabricated with about 28% reduction,the UTS and YS decreased slightly with increasing rolling temperature,while the EL first decreased slightly and then decreased dramatically at 500°C.