Study On Effect Of Buffer Layer On Hardness And Microstructure Of Titanium Alloy Welded Joint

Titanium alloys are one of the important lightweight metals and have a wide range of application prospects.For a long time,titanium alloys have been the focus of research in such disciplines as mechanical? mechanics and materials.Welding connection is the most common form of connection in metal structures,but the heterogeneity of the composition and organization of welded joints in metal welded structures is the root cause of non-uniformity in mechanical properties(especially fatigue resistance).In addition to welding common technical issues,titanium alloy welding itself still has some "difficult to solve" technical problems,such as the problem of precipitation phase.In this paper,the variation rule of the Vickers hardness distribution and the microstructure evolution of the TC17 titanium alloy welded joint was studied,and the selection criteria of the buffer layer material was established.The main research work is as follows:(1)Using TC17 titanium alloy as the base material,the causes of the weld softening caused by the conventional joints were analyzed.By introducing buffer layers with different chemical compositions and material properties,the variation rules of the hardness distribution curve and the evolution of the microstructure of various welded joints were studied,and the aim was to improve the joint softening and non-uniformity of the microstructure of the joints,and to determine The buffer layer material suitable for the TC17 titanium alloy welded joint is TC4 alloy.(2)For the above-mentioned welded joints,the relationship between the content of alloy elements and mechanical properties of welding materials and buffer layer materials in different joints and the hardness curve,microstructure distribution and precipitation phases of joints after welding was established,and a preliminary application for buffer layer selection basis of the welding of TC17 titanium alloys was initially established.(3)Through comparative analysis of conventional welded joints,it is found that the introduction of a suitable buffer layer material(ie,TC4 alloy)has significantly improved the roughness of the fracture surface of the welded joint,and the degree of weld softening has also been improved.