Effect of FSW Traverse Speed on Mechanical Properties of Copper Plate Joints

Abstract

The paper describes the influence of the friction stir welding travel speed on the mechanical properties of the butt joints of copper plates. The results of static and fatigue tests of the base material (Cu-ETP R220) and welded specimens produced at various travel speeds were compared, considering a loading applied both parallel and perpendicularly to the rolling direction of the plates. The mechanical properties of the FSW joints were evaluated with respect to parameters of plates’ material in the delivery state and after recrystallisation annealing. The strength parameters of friction stir welding joints were compared with the data on tungsten inert gas welded joints of copper plates available in the literature. The results of microhardness tests and fractographic analysis of tested joints are also presented. Based on the above test results, it was shown that although in the whole range of considered traverse speeds (from 40 to 80 mm/min), comparable properties were obtained for FSW copper joints in terms of their visual and microstructural evaluation, their static and especially fatigue parameters were different, most apparent in the nine-fold greater observed average fatigue life. The fatigue tests turned out to be more sensitive criteria for evaluation of the FSW joints’ qualities.

Microstructure and Mechanical Properties of Joints Depending on the Process Used

“…The highest values of microhardness were always recorded in the central zone of FZ of the weld [ 24 , 25 ]. This effect was independent of the side from which the analyses were carried out (face, ridge) [ 31 , 32 , 33 ].…”

“…The values of axial deformation for a given location within the scope of the weld were determined along the same lines indicated on both surfaces of the samples (i.e., on both sides of it) in the same cross-sections distant by 1 mm. In order to take into account the possible secondary bending effect, the deformations in the section under consideration were calculated as the average of the values determined on both sides of the sample [ 31 ].…”

“…This type of trend is characteristic of fusion joints [ 35 ]. The changes in the yield point were in each of the considered welding techniques symmetrical around the weld center line, which is qualitatively different compared, for example, to friction stir welds [ 31 , 36 ]. All the welded specimens ruptured in the cross sections away from the fusion zone, as shown in Figure 8 c For the material from weld center sections, the 0.2% proof stress (R 0.2 ) was not reached before specimen fracture, which indicates that it was higher than the ultimate tensile strength of the base material.…”

“…The relatively large range of changes in this ratio does not allow us to conclude the mechanical characteristics of the material only on the basis of the microhardness. Determining such a relationship would have to be limited to only one joining technique [ 26 , 31 ].…”

Recent Developments in Non-Conventional Welding of Materials

“…The application of the FSW process to other materials beyond the aluminium alloys and to dissimilar material combinations was also addressed in the present Special Issue. Machniewicz et al [ 4 ] studied the effect of the traverse speed on the mechanical properties of copper FS welds. For the traverse speed range tested by the authors, the effect of this parameter on the static and especially on the fatigue behaviour of the welds was found to be stronger than its effect on the weld macro and microstructure.…”