Assessment of Stray Grain Formation in Weld Joint of Single Crystal Molybdenum by ANSYS FE Simulation

Stray grains were observed in an electron beam welded (EBW) joint of single crystal molybdenum (Mo) in former studies. In the present paper, finite element (FE) method, combining the theoretical analysis, was used for evaluating the stray grain formation. Temperature-dependent thermal properties of molybdenum were incorporated in the model and a 3D volumetric moving double-ellipsoid heat source was applied. The relationship of parameter Φ, describing the degree of stray grain formation, to the thermal gradient G and the growth velocity V was used. Temperature and thermal gradient data of the model were extracted from simulation results under different operating conditions, and Φ was calculated. The effects of the welding parameters, including welding power Q and welding speed S on the formation of the weld stray grain were obtained.