Material flow observation for dissimilar friction stir welding of aluminum alloy and steel by X-ray CT method

Abstract

Dissimilar friction stir welding of aluminum alloy and steel is attractive method to fabricate light structure for transportation vehicle. The welding conditions, such as heat input (tool rotation speed and welding speed) and welding tool shape influence on the weld material and the material flow during welding. Control of material flow is important for fabrication of sound weld without defect. Thus, the material flow in the weld was investigated by using X-ray CT technique after welding. Chip of steel from weld interface was used as marker material for 3D visualization of material flow in aluminum alloy. From the observation, the heat input and probe shape affected on the material flow and formation of weld defect. Screw probe effectively stirred aluminum, induced downward and circumferential material flow around the probe and fabricated defect free weld with high weld strength.