Abstract
The synchronous acquisition system of droplet image inspection and arc electric signals were established and the droplet transition characteristics of aluminum alloys were researched in the plasma-MIG welding process. Typical droplet transition modes include globular transfer mode, short circuiting transfer mode, metastable spray transfer mode and projected transfer mode. The result indicates that MIG droplet transfer frequency and droplet transfer modes are changed by introducing the plasma arc in the plasma-MIG welding process compared with the MIG welding on the aluminum alloys, which broadens the range of welding parameters when the stable welding process proceeds. The metastable spray transfer and projected transfer mode are proved to be the most optimal modes by comparing the stability of electronic signal, droplet transition, weld appearance and weld penetration.