Measurements of Residual Stresses in Friction Welding Using the Hole Drilling Method

Friction Stir Welding is a solid-state process, which means that the objects are joined without reaching melting point. Which has demonstrated very high suitability for the joining of dissimilar aluminium alloys. The aim of this investigation was to study residual stress and micro hardness distribution in different zones of dissimilar friction stir welding of AA6061-T6 and AA7075-T6 and compare it with the tungsten inert gas (TIG) welding of AA6061-T6 by using increment hole drilling technique. Also The evolution of the residual stresses in the thickness direction was investigated, it was found that the maximum residual stresses are below the yield strength of the material in the shoulder region and showed that the longitudinal residual stresses in the joint were much larger than the transverse residual stresses. Vickers micro hardness measurements were performed in the transverse cross section of the samples, the results showed that Hardness peak values were observed in SZ region adjacent to the advancing side whereas low hardness regions were measured across the weld corresponding to the HAZ of both alloys and at the SZ adjacent to the retreating side.