High strength lap joint of aluminium and stainless steels fabricated by friction stir welding with cutting pin

Abstract

Dissimilar lap joints of aluminium and stainless steel were first friction stir welded by the tool with a cutting pin. The results showed that sound joints could be obtained by this method. When the pin was inserted into the lower steel sheet, macrointerlocks were formed by the steel flashes plugging into the upper aluminium at both sides of the nugget bottom. At the aluminium/steel interface, a thin intermetallic compound (IMC) layer and the mechanical bonding of microinterlocks were formed. In addition, the aluminium near the interface was also strengthened by grain refinement and IMC particles. Therefore, the beneficial effect of the macrointerlocks provided by the steel flashes was removed, the shear strength of the joint reached 89?7 MPa, which was even higher than that of the base metal of aluminium.

Electrically assisted friction stir welding for joining Al 6061 to TRIP 780 steel

“…This micro-interlock feature was also observed by Xiong et al (2012) when they did friction stir lap joint between Al 1100 and 1Cr18Ni9Ti stainless steel using a tool with cutting pin. According to their studies, the achievable joint shear strength can be even higher than the base aluminum alloy, which was reported to be mainly attributed to a thin IMC layer as well as mechanical bonding of the micro-interlocks at the Al-Fe interface.…”

Dissimilar friction stir welding of 6061 Al to 316 stainless steel using Zn as a filler metal

“…These attractive advantages make FSW intensively used in dissimilar welding [5][6][7][8][9] and studies published on the FSW of Al to steel in butt joint and lap joint are in a considerable number. Xiong JT [10] fabricated the lap joints of aluminium and stainless steel by FSW with cutting pin. Formation of the macro-interlocks resulting from the steel flashes plugging into the upper alminium at both sides of the nugget bottom and the mechanical bonding of micro interlocks were formed at the aluminum/steel interface.…”

“…In addition to these, numerical simulation was employed to optimize the Al/steel FSW [12]. There is a fact we can't ignore that even though successful FSW of Al/steel have been achieved and thick interlayer composed of brittle IMC were avoided, joint interface still exist a mass of brittle IMC such as FeAl, Al 5 Fe 2 and FeAl 3 [10][11][12][13], which could result in brittle fracture.…”

A review on friction-based joining of dissimilar aluminum–steel joints

“…Pin offset in Al leads to major plastic deformation of the Al material while partial deformation of the steel material, which causes the dispersion of steel particles and that consequently lead to mixing of steel particles into the Al matrix. 1,25,55,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] The size of these steel particles are dependent on tool pin offset majorly as well as heat input given by the process parameters of rotational speed, travel speed, and tool design. Another important parameter is the position of the workpiece, 1,53,89,90 wherein, effective material flow and enhanced mixing can be obtained when steel is kept at the advancing side and Al at the retreating side.…”