The Investigation On Microstructure And Properties Of W/Ti Multilayer Composites

Tungsten materials is the most promising plasma-oriented material for fusion reactor device in the future.However,the intrinsic brittleness of W materials,high ductile-brittle transition temperature and low recrystallization temperature limit its application.In order to improve the toughness of tungsten,based on the layered toughening principle of tungsten,this paper intends to use Ti foils as the toughening interlayer and successfully prepared W/Ti multilayer W-based composites by SPS.On this foundation,the microstructure and properties of W/Ti multilayer composites prepared by different sintering processes were systematically studied.The main conclusions can be drawn as follows:(1)During the sintering process,the interdiffusion of atoms between W layers and Ti layers had been done.Because of the isomeric transformation from HCP-BCC of Ti layer,the diffusion mode of W in the Ti layer is vacancy diffusion,while the diffusion mode of Ti in the W layer is mainly along the grain boundary of tungsten,so the diffusion depth of W in the Ti layer is deeper than that of Ti in the W layer.In addition,during the furnace cooling,? phase with basketweave microstructure or colonies microstructure were precipitated from the matrix ?-Ti.The relationship between the ?-Ti of the parent phase and the ?-Ti variant of the new phase maintained Burger orientation relationship,described as[0001]?//[110]? and[1120]?//[111]?.(2)When the sintering temperature below 1200?,the sintered sample interface can be divided into five region:Pure W(Region A),?-W(Ti)solid solution(Region B),?-Ti(W)solid solution(Region C)martensite with ?-matrix and ? phase in basketweave microstructure(Region D)and Widmanstaten structure with ? phase in colonies(Region E).The corresponding crystal structures were BCC,BCC,BCC,BCC+HCP,BCC+HCP.(3)Owing to the toughening of Ti layer,the comprehensive mechanical performance of the sintered W/Ti samples was better than as-received W foil.The tensile properties of the composites of 1200? is good.When the sintering temperature up to 1400?,the tensile properties of the material is the worst.Thus,the toughening mechanism of bonded composites can be summarized as follows:The toughness of the composite material by plastic deformation of Ti foils and the debonding effect of interface.The fracture mechanism of W layer is cleavage fracture and the fracture mode of Ti layer is micro-void gathered fracture when the sintering temperature below 1200?.However,plastic deformation of Ti foils and the debonding effect of interface disappeared.The fracture mechanism of W layer is intergranular brittle fracture and the fracture mode of Ti layer evolve into cleavage fracture when the sintering temperature up to 1400?.