Tool-workpiece interaction and shear layer flow during外文书.pdfVIP

Tool-workpiece interaction and shear layer flow during friction stir welding of aluminium alloys Z. W. CHEN, S. CUI Department of Mechanical and Production Engineering, AUT University, New Zealand Received 15 July 2007; accepted 10 September 2007 Abstract: Material flow phenomena during friction stir welding (FSW) and the forming mechanism of “onion rings” are complicated and currently not fully understood. In the present FSW study aluminium alloys 5083 and A356, with the latter more readily welded than the former, were used. The experiments were conducted to obtain samples of tool and workpiece “frozen” together during FSW for analysis. Two deposition modes for forming the weld nugget zone were observed, one for each alloy with the present FSW parameters. The first is the deposition of shear layers forming the “onion rings” in 5083 alloy nugget. The tool-workpiece interaction leading to the layer thickness being equal to the ratio of welding speed and tool rotation speed is suggested. The second mode is the combination of depositing the rotational shear material in the lower part on the advancing side and the drag flow of material from the retreating site forming the rest of the A356 nugget. The latter mode resulted in the absence of a clear ring structure. Key words: friction stir welding (FSW); deposition; nugget zone; rotation 1 Introduction Friction stir welding (FSW), invented by TWI in 1991, is a relatively new solid-state joining and efficient manufacturing enabling technology. Many aspects of FSW have been studied quite extensively in recent years and comprehensively reviewed by MISHRA and MA[1]. They concluded that material flow during FSW is complicated and not well understood. REYNOLDS[2], in presenting a