Effect of Heat Input On The Microstructure And Mechanical Properties Of Ti180 Titanium Alloy Electron Beam Welding Joints

The amount of welding heat input will affect the α/β phase transition in the heat-affected zone of the duplex titanium alloy joint and the precipitation of the secondary α' phase, thereby changing the mechanical properties of the joint. The microstructure analysis of the 7 mm thick Ti180 titanium alloy electron beam welded joints found that the near-fusion line heat-affected zone and the central heat-affected zone are composed of "ghost"-shaped primary α-phase, secondary needle-shaped α'-phase and residual β-phase, and the near-base material heat-affected zone is composed of primary α-phase, residual β-phase and a small amount of secondary α-phase. The increase in heat input will promote a decrease in the proportion of nascent α, resulting in changes in the tensile properties of the joints. The heat input is increased from 120 J·mm-1 to 177 J·mm-1, and the elongation is reduced from 16.7% to 11.6%, which is lower than the base material (18.7%); the tensile strength is increased from 1010 MPa to 1070 MPa, and the strength of the base material (970MPa) is reached. In addition, the hardness of the weld area and the heat-affected area under the heat input conditions of 120 J·mm-1~177J·mm-1 is always higher than that of the base material area. In summary, the mechanical properties of Ti180 titanium alloy joints can be regulated by changing the welding heat input and controlling the phase transition behavior in the heat-affected zone.

Ti180 Titanium Alloy Electron Beam Welded Joint

Ti180 Microstructure of Base Metal

Ti180 Titanium Alloy EDS Surface Scanning Results

Ti180 Microstructure of The Middle Weld Zone of Electron Beam Welding Joint

Ti180 Microstructure Characteristics of Heat Affected Zone of Electron Beam Welded Joint

Changes of Microstructure in Different Locations of Heat Affected Zone Under Four Kinds of Heat Inputs

Hardness Distribution of Ti180 Welded Joints Under Different Heat Inputs

Tensile Properties of Ti80 Electron Beam Welded Joints with Different Heat Inputs

Tensile Fracture Morphology