Microstructures And Mechanical Properties Of Electron Beam Welded Ti60 Titanium Alloy To GH3128 Nickel Alloy Joints

Electron beam welding experiments of Ti60 titanium alloy to GH3128 nickel alloy were carried out. It was analyzed that the main problems existed in the direct welding of Ti alloy and N i alloy. The influence of single component C u or V as filler metal and C u C r alloy o r C u2 V alloy as filler metal on the microstructure and mechanical properties of the joints was studied. And electron beam welding experiments of Ti60 to GH3128 were carried out with C u/V gradient filler metal. Microstructures of the joints were examined by optical microscopy, scanning electron microscopy and X-ray diffraction.The mechanical properties of the joints were evaluated by tensile strength and microhardness tests. The fracture surfaces of the joints were also analyzed.Direct electron beam welding of titanium alloy and nickel alloys show that Ti/Fe joints cracked after welding. A large amount of brittle Ti N i/Ti2 N i formed in the join. So that the hardness of the joint was 900 HV, which limits the effective connection of the joint. The C u component as the filler metal of titanium / nickel welding joint achieve both effective connection, the microstructure composed of solid solut ion and compound, the presence of solid solut ion can improve the weld plastic and helps to reduce internal stress. The amount of meltin of the base metal was affected by beam current and speed, so that to influence interfacial compound layer thickness and control the mechanical properties of the joints. The tensile strength of the joint with copper filler metal can reach 228 MPa, and the location of the fracture in recent titanium side. The joint of titanium / nickel with vanadium filler metal made of titanium based solid solution, vanadium based solid solution and N i3 V, N i V3 intermetallic compounds composition, and thickness of the compound layer limits the joint properties, the tensile strength can reach a maximum of 163 MPa. The highest microhardness in the near nickel side was 92 4 HV, which greatly increased the brittleness of the weld and decreased the mechanical properties of the joints.Based on the experiment of adding a single element as a filler metal, the C u Cr alloy and C u2 V alloy were added as the filler metal of titanium/nickel electron beam welding. The C u Cr alloy filler metal and the way of the nickel side down, obta ined a nickel based solid solution + copper based solid solution + chromium based solid solution +Ti2Cu/α- Ti of the microstructure of the joint, so that the tensile strength increased to 264 Mpa. The poor mechanical properties of the C u2 V alloy as the filler metal of the titanium nickel welded joint is due to the presence of a large Ti-N i-C u phase in the weld, and the tensile strength is only 173 MPa.In order to improve the performance of Ti/N i electron beam welding joint, in the middle of the base metal added C u/V gradient fill layer on the welding. The microstructure form that Ti60/(Ti, V) +V(s, s) +Ti C u/V(s, s) +C u(s, s)/N i(s, s) /GH3128 was obtained. According to the adjustment of welding path number and welding sequence, a better welding joint was obtained, and the tensile strength was 392 MPa, which reached 47 % of nickel alloys.