As an effective method for the fabrication of miniature metallic parts, the development of micro-forming process (MFP) is still restricted by the existence of size effect. To improve the micro-forming performance of metal material, ultrasonic vibration assisted MFP had been studied extensively for its superiorities in improving materials flow stress and reducing interfacial friction. However, from the literature available, the high frequency vibration was usually found to be superimposed on the forming tool while seldom on the workpiece. Our group developed a special porous sonotrode platform which can realize tool vibration and workpiece ultrasonic vibration independently. In this work, ultrasonic micro-extrusion experiments for copper T2 material under tool vibration and the workpiece vibration condition, respectively, were conducted for comparing the micro-forming characteristic of different vibration modes. The micro-extrusion experiment results of copper T2 show that the lower extrusion flow stress, the higher micro-extrusion formability and surface micro-hardness, and more obvious grain refinement phenomenon can be obtained under the workpiece vibration condition compared with that of tool vibration. These findings may enhance our understanding on different ultrasonic forming mechanisms and energy transmission efficiency under two different vibration modes.
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