Feasibility of Friction Stir Welding for Joining and Microstructure Refinement in a ZK60 Magnesium Alloy

Feasibility of FSW to produce defect-free welds and for microstructure refinement in a ZK60 magnesium alloy has been examined over wide ranges of rotational and welding speeds. The results showed that joined-state was affected very much by the thickness of plates to be joined: for ‘‘thin’’ 3-mm thick plates, FSW was successful in a relatively wide range of welding conditions, whereas all ‘‘thick’’ 6-mm welds were found to be defective irrespective of rotational and welding speeds used. We have demonstrated that FSW is a very effective tool for microstructure refinement in the ZK60 alloy plates: A coarse, mm-scale, original grain structure was efficiently refined down to fine-grained range. It appears that second-phase particles containing Zr play an important role in the grain refinement. [doi:10.2320/matertrans.MRA2007177]