Study On The Titanium/Stainless Steel Bimetallic Tube Diffusion Bonded By Inner Pressure

With the development of modern science and technology, a single material can not meet human’s needs. Composite materials arise at the historic moment. Composite materials have a wide variety, and laminar composite metal is one of the hotest topics in the study of material science. Metal composite tube is a kind of laminar composite metal. It makes up for the defect of the single tube, at the same time more excellent performance is received and the cost is lowered. It is widely used in petroleum, chemical, electric power, energy and other industries. Direct composite of titanium and stainless steel metal tube is very difficult, putting in a reasonable interlayer can solve this problem. So the study on adding an interlayer to the titanium and stainless steel composite has a special significance.The composite tube of commercially pure titanium and stainless steel304(SS) was prepared by the drawing and inner pressure diffusion technique using copper foil as an interlayer. The interface microstructure, chemical composition, fracture morphology and phases were measured by OM, SEM, EDS and XRD. The shear strength and microhardness near the interface were tested by shear and microhardness tests. The influences of different diffused processes on microstructure, element distribution and properties of interface have been analyzed.The results of microstructure analysis show that titanium/stainless steel can achieve combination by the drawing and inner pressure diffusion technique. At850℃titanium/copper interface formed α-Ti, α-β Ti microstructure and Ti-Cu intermetallic. Above900℃, lamellar widmanstaten structure α-β Ti, β-Ti microstructure and Ti-Cu intermetallic were appeared near the titanium/copper interface. At1000℃,Ti-Cu-Fe ternary solidified structure was formed in the copper interlayer.Interface component analysis shows that at the range of the study temperatures, the atomic interdiffusion phenomenon was founded near the interface. At850℃, a thick diffusion layer was formed at the titanium/copper interface. Interlayer effectively prevents elements Ti and Fe from forming brittle intermetallic compounds. Above900℃, Ti elements across the interlayer, brittle intermetallic compounds were formed at the copper/stainless steel interface. So at this moment, the interlayer can’t segregate titanium and stainless steel.Hardness tests and shear tests show that because the elements interdiffusion and the intermetallic compounds were formed in the interface, so the maximum microhardness value and the position of fracture were appeared in this interface. The shear strength of the interface first increases and then decreases with the rising heating temperature, and it first increases and then decreases with the extension of holding time.