Evaluation of the homogeneity of the metal of welded joints by ultrasonic computed tomography

We consider the possibilities of a new (in the field of the ultrasonic testing of present-day structural materials) information technology of ultrasonic computed tomography for the diagnostics of the quality of welded joints and control of the parameters of welding technological processes, including the technology of electron-beam welding of present-day aluminum alloys. This kind of diagnostics is based on the obtained information on the volume homogeneity of mechanical properties of the metal under consideration in the heat-affected zone of a weld. Analysis of the information aspects of the method of transmission ultrasonic computed tomography shows that the technologies of ultrasonic testing based on it are the most efficient for thick-walled plane-sheet articles with welded joints because high-quality reconstruction of the space distribution of the parameter under study over the article thickness is possible if this parameter changes in the plane parallel to the article surface. We describe the results of tomographic experiments with the use of a UST-04M ultrasonic computer tomograph, developed at the Physicomechanical Institute, on the reconstruction of the space distribution of acoustic and mechanical characteristics of the metal in specimens of the mentioned articles, made of steel and AMG-6v aluminum alloy by the technology of electron-beam welding, as well as the data of verification of the reconstructed tomographic images by means of their comparison with the results of metallographic investigations. The data obtained corroborate the efficiency of the technology of ultrasonic computed tomography for evaluating the quality of welded joints and optimizing welding technologies on the basis of experimental determination of the volume homogeneity of properties of the metal in the zone of a welded joint.