Effects of Geometrical Feature on Microstructures and Mechanical Properties of Refill Friction Stir Spot Welding 6061 Aluminum Alloy

Abstract

Refill friction stir spot welding (refill FSSW) is a solid state joining technology developed and patented by Helmholtz-Zentrum Geesthacht. Refill FSSW is a welding process suitable for spot joining lightweight materials in similar and dissimilar joint configuration. The result is a spot welded in lap configuration with minimal material loss and a flat surface with no keyhole. In the present study, refill FSSW was applied to join the similar 6061 aluminum alloy sheet with 1.25 mm thickness. The objective of this work is to investigate the influence of the hook on the microstructure and mechanical properties of the weld. The hook is a geometrical feature, formed as a result of the upward bending of the sheet interface during the sleeve plunge and retraction during welding. The weld strength had a negative correlation with the hook height, however it was concluded that the shape of hook changes according to the combination of process parameters. The highest value of the lap shear corresponded to the smallest hook height.

Effect of Tool Pin Geometry and Process Parameters During FSW of Dissimilar Alloys of Mg

“…In addition to this, welding together dissimilar alloys of Mg and welding of alloys of Mg with other metals using classical techniques of joining is not an easy task, due to the alloy's inferior resistance towards corrosion and faster chemical reactivity 9 . Likewise, attempts to join alloys of Mg using larger input of heat energy will result in coarsening of grains in the seam of the joint, due to the alloy's larger thermal conductivity and low point of melting 10,11 .…”