Microstructural characterization and mechanical properties of TIG weld joint made by forged Ti–4Al–2V alloy

Abstract

The weld of titanium alloy promotes the complex components to be widely utilized in various fields. It is necessary to investigate the microstructure and mechanical properties to ensure the reliability of weld joint. In the present study, the microstructure, texture and mechanical properties of a joint made of the near-α titanium alloy Ti–4Al–2V, prepared by multi-layer and multi-pass TIG welding process, were investigated. The results show that the heat affected zone (HAZ) and fusion zone (FZ) are composed of α′ martensite, acicular α and lath like widmanstätten α + β, which is complex than that of the base metal (BM). Meanwhile, the texture in HAZ and FZ, including {0001} <11–20> plate texture, {11–20} <10-10> plate texture, and {11–20} <0001> plate texture, are also complicated than that of BM ({0001} <11–20> plate texture), and the texture intensity is also higher. Besides, the mechanical properties of the FZ are inferior, due to the microstructure and mechanical properties evolution. Specifically, the tensile strength of the BM, upper part and bottom part of FZ are 695 MPa, 644 MPa, and 679 MPa and the impact energy of the BM and FZ are calculated as 201.7 J/cm2 and 70.7 J/cm2, respectively. The hardness of the FZ (200–220 HV1) is lower than that of the BM (230-250 HV1). This study first comes to attention to systematically characterize and analyze the weldability, as well as the microstructure evolution and mechanical properties of the weld joint, of Ti–4Al–2V alloy, which will lay a solid foundation for the engineering application of this alloy in the future.