Analysis of the Oscillation Behavior of Hybrid Aluminum/Steel Joints Realized by Ultrasound Enhanced Friction Stir Welding

Abstract

Friction stir welding (FSW) is an innovative solid-state joining process, which is suitable for joining dissimilar materials with strongly differing physical and chemical properties such as aluminum and steel. Where other joining methods such as fusion welding struggle to achieve appropriate joint strengths due to the excessive formation of brittle aluminum-rich intermetallic phases (IMP), FSW joints of aluminum and steel only show small layers of IMP, thus, sufficient tensile strengths in proximity to the maximum tensile strength of the weaker aluminum base material can be reached. With the aim to optimize the mechanical and microstructural properties of such dissimilar joints for widening the field for possible industrial applications, several hybrid friction stir welding methods have been developed which include an additional energy input, whereas the ultrasound enhancement (USE-FSW) is one of the most promising. The current work was carried out on AA6061/DC04 joints which were successfully friction stir welded with and without ultrasound support, in respect to the influence of varying the ultrasound transmission side. The functionality of the USE-FSW setup could be verified by multi point laser vibrometer measurements. Additionally, a higher proportion of transversal oscillation for the transmission of power ultrasound into aluminum could be detected using a scanning vibrometer. In comparison to the conventionally friction stir welded joints the ultrasound enhancement led to an avoidance of weld defects and an increase of the steel particle volume in the stir zone. The joint produced with power ultrasound transmission via aluminum resulted in a more uniform interface.

Effects of Rapid Cooling on Properties of Aluminum-Steel Friction Stir Welded Joint

“…One of the main issues in the dissimilar FSW is the thermal, mechanical, and chemical properties difference of two metals like aluminum and steel or titanium. This causes defects at the weld zone such as wormhole, tunnel defect, or micro-cracks [ 27 ]. Figure 2 shows the thermal history of steel (advancing side) and aluminum (retreating side) during the welding process recorded by NT1, NT2, and NT3.…”

“…At first, the FSW process was used for aluminum alloys [ 6 , 12 , 13 , 14 ]; however over time, the capacity and potential of FSW proved that this method could be employed not only for aluminum alloys, but also for other purposes such as joining of similar and dissimilar polymeric and metallic materials [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. One of the useful structures that can be made by FSW is a steel-aluminum dissimilar joint [ 12 , 26 , 27 ]. This joint is a new class of dissimilar structure that can be used in various components in order to lighten up structures [ 13 , 28 , 29 , 30 ].…”

The Effect of Friction Stir Welding Parameters on the Weldability of Aluminum Alloys with Similar and Dissimilar Metals: A Review

“…In order to produce hybrid Al/steel joints by ultrasound assisted FSW, [150] looked into the oscillation behavior of these joints. The deep drawing steel DC04 with dimensions of 280 mm x 100 mm x 3 mm and the aluminum alloy AA6061 were used for welding.…”

“…FSW can be used to successfully create the different connections of AA6061 and DC04. [150].Re. [150] was MDPI, required no permission).…”

Comparison of process behavior, microstructure and mechanical properties of ultrasound enhanced friction stir welded titanium/titanium joints

“…On the other hand, the occurrence of the acousto-plastic effect can reduce the yield stress of the joining partners [16]. The combination of these two mechanisms of action results in numerous advantages, including the plasticization of a larger volume of material, more homogeneous stirring of the joining zone, better through-welding and the reduction or avoidance of intermetallic phases (dissimilar composites) and oxide layers (similar composites) [17][18][19][20][21]. So far, there is no literature on the application of power ultrasound enhanced friction stir welding on similar titanium/titanium joints and subsequent investigations on the process behavior as well as microstructural and mechanical properties.…”