Coupled thermodynamic/kinetic model for hydrogen transport during electron beam welding of titanium alloy

Abstract

Hydrogen transport during the welding of titanium alloy Ti–6Al–4V is analysed. A coupled thermodynamic/kinetic treatment is proposed in which the driving force for hydrogen migration is its chemical potential gradient, which is in turn calculated using the Thermo-Calc software package. The model is applied to the case of the electron beam welding of Ti–6Al–4V, for which a simple process model is presented for the temperature evolution expected. There is a thermodynamic driving force for accumulation of hydrogen in the weld pool. However, agreement with the limited amount of experimental data in the literature for the hydrogen field caused by welding indicates that account needs to be taken of the hydrogen degassing from the weld pool.

Keywords:

• Hydrogen diffusion
• Titanium welding
• Porosity formation
• Thermodynamic and kinetic modelling

The authors are grateful to the Engineering and Physical Sciences Research Council (EPSRC) of the UK and to Rolls-Royce plc for sponsorship of the present work via a Dorothy Hodgkin Postgraduate Award.