Accuracy improvement of X-ray residual stress measurement in welds of Ni based alloy by two-dimensional detector with multiaxial rocking

In materials such as Ni based alloys, the microstructures are formed by monophase solidification without solid state transformation. It is difficult to obtain the welding residual stress by X-ray diffraction because of the preferred orientation of the unidirectional solidification and the grain growth in the heat affected zone. To exclude their effect, a method that records the diffraction peaks in a two-dimensional detector combined with multiaxial rocking is proposed. It is clarified that the equilibrium of shrinkage and the recovery of strain during the thermal cycle determines the site of the maximum tensile stress. In addition, dynamic recrystallisation, which occurs during welding, contributes to the decreased residual stress at the fusion line. If the spatial resolution of the proposed and the conventional measurement methods can be correlated, the results of each method agree well. Therefore, the proposed method is an effective tool for measuring the residual stress in welded joints of Ni based alloy.