T. J. McInerney, R. B. Madigan, Montana Tech of the University of Montana, Butte, MT; P. Xu, C. E. Cross, BAM, Berlin, Germany

Summary: A novel method has been developed to precisely control the mechanical oscillation of the weld pool, varying frequency and amplitude independently to achieve solidification grain refinement. Grain refinement has been found to occur only under very specific conditions of imposed frequency and amplitude of excitation. Arc voltage measurements have been used to monitor the response of the weld pool. Possible reasons for this observed behavior will be discussed.