Multiscale investigation of microstructure optimization in the arc additive manufacturing and arc welding by self-induced ultrasound

Abstract In the arc welding and arc additive manufacturing processes, utilizing self-induced ultrasound has attracted widespread attention for obtaining intensive arc plasma and optimizing metallurgical characteristics of molten pool, featuring with increased penetration, suppressed dendrites and refined grains in the deposited layer and weld joint of metal. However, the ultrasound emitting mechanism remains unclear and process optimization remains limited by incomplete understanding of ultrasound in the arc plasma and molten pool. In our work, Multiscale experiments and modeling (MHD and MHD waves modeling at meso scale, coupled phase-field and fluid flow modeling and fluid-structure modeling at micro scale) are proposed to reveal the physical essence of ultrasound generation, ultrasound induced streaming, suppressed dendrites growth and dendrites fragmentations. It demonstrates the effectiveness and efficiency of utilizing self-induced ultrasound in controlling microstructures of 316 stainless steel with a maximum of 24% decrease in grain size and transition from anisotropy orientation to isotropy orientation, and concrete directions of process optimization arc identified for facilitating the successful industrial use. We expect introducing self-induced ultrasound energy could be a more efficient and cost effective technology for controlling of microstructure in the arc metal processing related fields.