Effects of pin diameter on the tool plunge stage in friction stir welding

In this paper, the plunge stage of friction stir welding process has been investigated. Effect ofpin diameter on the temperature distribution in the workpiece and its microstructure has beenexamined experimentally. By using the tools with different pin diameters tests were done andtemperature at four points of workpiece was measured during the tool penetration. The resultsshowed that the diameter of the pin had significant effects on the workpiece temperature.Increasing the diameter of the pin was decreased the final temperature of each point ofworkpiece because the effective friction surface was decreased. Temperature distributionaround the tool was clearly asymmetric and the highest temperature was in the back of thetool at trailing edge. At the end of the plunge stage temperature of each point was almostfixed at constant temperature and the process reached a steady state condition. Themicrostructure of the samples was similar to each other. In the microstructure studies fourareas with different microstructure were observed at the cross section of the workpiece. Thesize and orientation of the grains were different with others. Extent of the areas was affectedby pin diameter. The extent of the stir zone and thermomechanical affected zone were reducedby decreasing the pin diameter.

Keywords:

FSW , plunge stage , temperature distribution , pin diameter , microstructure