Accuracy Improvement of X-Ray Stress Measurement on GTA Weld of Type 600 Ni Based Alloy
Tadafumi HASHIMOTO, Yusuke OSAWA, Shinro HIRANO, Masahito MOCHIZUKI and Kazutoshi NISHIMOTO
Abstract:In materials such as Ni-based alloys, the microstructures are formed by mono-phase solidification without solid-state transformation. Measuring the welding residual stress by X-ray diffraction is difficult because of the preferred orientation of the unidirectional solidification and the grain growth in the heat-affected zone. To exclude these effects, a method that records the diffraction peaks in a two-dimensional detector combined with multi-axial 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 re-crystallization, which occurs during solidification, 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. Key Words:Welding residual stress, Ni based alloy, X-ray stress measurement, Two-dimensional detector, Multi-axial rocking, Dynamic re-crystallization