Microstructure and Mechanical Properties of the Electron Beam Welded Joint of a New High-Strength Metastable Beta Titanium Alloy

Author of the article:ZHANG Xinquan 1,2 , LI Jinshan 1,3 , TAO Manfei 1 , CHEN Biao 1,3

Author's Workplace：1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China; 2. The First Aircraft Institute of AVIC, Xi'an 710089, China; 3. Innovation Center NPU Chongqing, Chongqing 401135, China

Key Words： Ti-45551 alloy; electron beam welding; base metal state; microstructure; mechanical property

Abstract：A new high-strength metastable β titanium alloy Ti-4Al-5Mo-5Cr-5V-1Nb (Ti-45551) was studied by electron beam welding on forged, solid-solution and solid-solution aged titanium alloy plates with a thickness of 20 mm. The microstructure and mechanical properties of electron beam welding joints under different base metal states were studied. The results show that the fusion zone of the three kinds of welds consists of coarse β column crystals, and no α phase exists in each region of the welded joint under the condition of solid solution+welding (SW), while the ghost α phase is found in the heat affected zone due to the heat input energy decreaseing with the distance from the weld center under the conditions of forging+welding (FW) and solid solution aging+welding (AW). The content of the "ghost α phase" increases with the distance from the weld center. The tensile strength and plasticity of the three welded joints are similar, approximately 760 MPa and 7.5%, respectively, which is attributed to the formation of a coarse columnar β crystal structure in the fusion zone, and the concentration of strain in the zone, resulting in a decline in the strength of the welded parts and finally fracture in the fusion zone.