Effect of Rotational and Transverse Speeds on Friction Stir Welded Plates

Friction-stir welding (FSW) is a solid-state joining process (meaning the metal is not melted
during the process) and is used for applications where the original metal characteristics must
remain unchanged as far as possible. This technology has been implemented in the aerospace,
rail, automotive and marine industries [3]. The objectives of the project are to study the
difference of the welded region occurred within the 6061-T6 Aluminum alloys when they
undergo the FSW process and to study the effect of rotational and transverse speeds against the
hardness of the welded region. This project focuses on 6061-T6 Aluminum alloy; tool steel H13
and the development of microstructural features within the welded area. Data gathering and
research about tools and equipments and the investigations of the Friction Stir Welding (FSW) as
the joining method are done. The welding tool for the FSW needs a special design in order to run
onto the workpiece. The author decides to go with the basic design; compared to other models
available in the industry. Two plates of 100mm x 100mm x10mm 6061-T6 Aluminum alloys are
to be set up butted-joint and clamp rigidly to perform the welding operation. The project is
started by having the tool prepared by designing, fabricating and heat treatment. Next, the tool
and the workpieces are set up in the CNC MAZAK Milling Machine for the welding procedure.
Samples from the larger workpieces are taken by sectioning and are mounted. The samples need
grinding, polishing and etching to properly examine the microstructure. After the difference of
the welded region is examined using optical microscope, hardness of the samples are taken to see
the effects of the rotational and transverse speeds. It can be observed that there could be up to
four different welded regions which are the unaffected region (parent material), the heat affected
zone (HAZ), thermo-mechanically affected zone (TMAZ) and the stir nugget as shown in
Chapter 4 of this report. The hardness of the welded region increases at it approaches the weld
line because of the grain refinement of the welded region. The grains of the welded region had
been refined when the welded plates were exposed to work and heat which alters its hardness.