Effect Of Ti Intermediate Layer On The Microstructure And Properties Of W/Ta Multilayer Composites

Tungsten(W)multilayer composites are an important method to improve the toughness of W.The toughening layer and interface structure are very important for their properties.Ta is considered as one of the ideal ductifying laminates in W laminates due to its high melting point and high plasticity.However,due to the tensile strength and fracture toughness of the W/Ta multilayer composite material are both low.In order to further improve the strength and toughness of W/Ta multilayer composites.In this paper,a W/(Ti/Ta/Ti)multilayer composite was obtained by adding Ti intermediate layer between W layer and Ta layer,which can greatly improve the comprehensive mechanical properties of W/Ta multilayer composite.On this basis,the effects of Ti interlayer on the microstructure and mechanical properties of W/Ta multilayer composites were studied.The main conclusions are as follows:(1)After diffusion bonding,the interface between titanium and tantalum disappears.At this time,the interface is W/Ti interface with weak bonding strength,and the toughening layer is Ti/Ta/Ti layer.The formation of W/(Ti/Ta/Ti)multilayer composites can greatly improve the comprehensive mechanical properties of W/Ta multilayer composites.Moreover,With the increase of the thickness of Ti layer,the tensile strength,elongation and bending strength of the composite increase.(2)The microstructure of W/(Ti/Ta/Ti)multilayer composites with different Ti thickness is different.When the thickness of Ti layer is less than 50 ?m,pure ?-Ti and?-Ta solid solutions are formed in the Ti layer.When the thickness of Ti layer is greater than 80 ?m,the Ti layer consists of ?-Ti and ?-Ta single-phase regions near the interface and ?-Ti+?-Ti double-phase regions in the middle.(3)In the diffusion bonding process,both W and Ta elements diffuse into the Ti layer,Both W and Ta diffused into the Ti layer can stabilize ?-Ti and strengthen the solid solution.However,the solid solution strengthening effect of W is much better than that of Ta.The tensile strength of W/(Ti/Ta/Ti)multilayer composites is much higher than that of W/Ta multilayer composites,because the strength of Ti/Ta/Ti layer is much higher than that of Ta layer.The tensile strength of these composites is in good agreement with the results calculated by the hybrid model considering the interfacial stress concentration factor.(4)The fracture mechanism of W/Ta multilayer composites is very different from that of W/(Ti/Ta/Ti)multilayer composites.Due to the high interfacial bonding strength between the W layer and the Ta layer,the W/Ta layered composites usually do not appear interface cracking phenomenon,which leads to the plastic deformation of the Ta layer is limited,and the tunnel crack is easy to appear in the W layer.However,W/(Ti/Ta/Ti)multilayer composites are prone to interfacial cracks at the W/Ti interface.The cracking of the interface makes the stress state of Ti/Ta/Ti layer change from plane strain state to plane stress state,which is beneficial to the plastic deformation of the ductile layer,and makes the toughness of W/(Ti/Ta/Ti)multilayer composites much higher than that of W/Ta multilayer composites.(5)The DBTT of W/Ta laminated composites is about 400?,and the material shows good plasticity at 400?.When the thickness of the Ti interlayer is greater than 50?m,the DBTT of the material can be reduced to 200?.Moreover,The tensile strength and elongation of W/(Ti/Ta/Ti)multilayer composites are greater than that of W/Ta multilayer composites.In general,with the increase of temperature,the tensile strength of W/(Ti/Ta/Ti)multilayer composites increases first and then decreases,while the elongation increases all the time.