Microstructure and fracture behavior of friction stir lap welding of dissimilar metals

Abstract

Friction Stir Welding (FSW) is a relatively new solid state joining technique which is used not only for joining the aluminum and its alloys but also has potential for joining dissimilar materials with very different physical and mechanical properties which are hard to weld using conventional fusion welding processes. Tensile shear testing is used to determine the Mechanical strength of friction stir lap (FSL) welds under static loading, fracture strength (σLap) corresponding to the maximum load in a test over the sample width is widely used as the strength value. During friction stir lap welding (FSLW) of dissimilar metals with large differences in melting temperatures, a metallurgical bond is established through the formation of interfacial intermetallic compounds. However, as these intermetallic compounds are generally believed to be brittle with little ductility, they are generally considered to have detrimental effect on fracture strength. The aim of the present research is to study how the interface structure is affected by FSW parameters and how the formation of interface structure affects fracture of Al-Steel and Al-Ti FSL welds.

Microstructure and fracture behavior of friction stir lap welding of dissimilar AA 6060-T5/ Pure copper

“…In this case, although there can still be an absence of intermetallic layer and MSZ, but it is totally different in case of Al-steel FSLW. Shubhavardhan and Surendran (2018), because as has already explained the thermal conductivity of steel is lesser than copper, the reason could be steel conducted heat far slower than the copper, forming a thin and continuous intermetallic layer at Al-Steel FSLW interface for Dp≈0. A thin Al-Cu interface intermetallic compound layer can form when pin penetration Dp is 0.4mm, metallurgical bonding the top and bottom plates together, as demonstrated by an example shown in Fig.…”

“…8(a) is the first example where no intermetallic compound layer (IMC) were formed for Dp≈0, It should be noted that there is no research work available in literature for this condition especially for Al-Cu FSLW. The reason for not forming any intermetallic layer at the Al-Cu weld interface may be because copper has conducted heat faster, since copper has higher thermal conductivity, but for the similar FSLW conditions (pin penetration, Dp≈0) for Al-Steel FSLW, a continuous and thin intermetallic layer has been reported (Shubhavardhan & Surendran 2018). This is just to compare the effect of FSLW pin penetration (Dp) on different large ∆T Melting couple, however, FSLW of Al-steel and Al-copper is totally different, cannot compare the results), with maximum value of σLap.…”

Tailoring of Dissimilar Friction Stir Lap Welding of Aluminum and Titanium

“…This simple approach reduces tool abrasion while also localizing the spatial distribution of titanium fragments in a relatively small area [ 1 , 3 , 10 , 22 ]. Moreover, the minimizing of the interaction between the welding tool and titanium lowers the FSW heat input [ 2 ] and, thus, shrinks the intermetallic layer [ 1 , 5 , 6 , 13 , 15 , 22 , 32 , 34 , 35 ].…”

Mechanical and fracture properties of aluminium cylinders manufactured by orbital friction stir welding

“…Dealing with the FSW process, most of the previous research works are focused on linear welding of plates (such as lap, butt and T‐joint welds) for different alloys 3–15 . However, reliable and practical usage of this technique for joining cylinders, pipes and tubes requires a suitable and optimized orbital FSW on cylindrical shells.…”