Study On The Microstructure And Properties Of Ti/Ni/Ti Composites Prepared By Rolling Thinning

Metal layered composites rely on its excellent overall performance,simple processing technology,low cost and other people by the widespread concern.In this paper,Ti/Ni/Ti three-layer composite was prepared by rolling composite technique.The macroscopic morphology,microstructure and interface of the composites were observed by optical microscope and scanning electron microscope.The microhardness and tensile testing to study the mechanical properties of composite materials.The interfacial bonding mechanism,microstructure and mechanical properties of the composites during the rolling deformation were studied.The effects of annealing time and temperature on the growth of diffusion layer and the effect of interface structure on the mechanical properties of Ti/Ni/Ti composites were investigated by heat treatment.The results showed that the interface bonding and comprehensive mechanical properties of Ti/Ni/Ti composites were better than Ni/Ti/Ni under the same rolling conditions.The tensile strength and elongation of Ti/Ni/Ti were 627.67 MPa and 12.3%,respectively.The tensile strength and elongation of Ni/Ti/Ni were 735.60 MPa and 4.8%,respectively.After 90% reduction in rolling rate,diffusion heat treatment by different temperatures and time,the composite material had two layers of diffusion layer before annealing at 600 ? for 4h,and then grew into three layers after 4h,and according to phase diagram and energy spectrum analysis of these three components were Ti2 Ni,TiNi,TiNi3 three intermetallic compounds.With the increase of heat treatment temperature and time,the thickness of the diffusion layer gradually increases,90%deformation under the annealing temperature of 800 ? for 32 h,the diffusion layer thickness of 45?m.and the content of the intermetallic compound gradually increases,the tensile strength of the composite material gradually increases,and the elongation gradually decreases,800 ? annealing 8h composite tensile strength reached 495.9MPa,but the elongation has dropped to 5%.90% deformation under the annealing temperature of 800 ? for 32 h,the diffusion layer thickness of 45?m.The formation process of the interface diffusion layer was first nucleation by the diffusion point,and then grew into a discontinuous diffusion island,and finally form a complete diffusion layer.After annealing at 600 ? for 2h,the interface of the composites was composed of two layers.There were two kinds of intermetallic compounds.TiNi and TiNi3 and TiNi3 have crisp and bad ductile,respectively,which led to the decrease of tensile strength and plasticity.The hardness of the matrix layer increased with the increase of temperature and time,annealing at 700 ? for 32 h,the Vickers hardness of the titanium matrix was177.7HV,and the nickel matrix was 123.4HV.The tensile strength of composite material was 495.9MPa,but the elongation decreased to 5%.