The Role of Mechanical Connection during Friction Stir Keyholeless Spot Welding Joints of Dissimilar Materials

Abstract

Abstract:Contrast experiments of lap joints among dissimilar AZ31B Mg alloy, Mg99.50, zinc-coated DP600 sheet, and non-zinc-coated DP600 sheet were made by friction stir keyholeless spot welding (FSKSW) and vacuum diffusion welding (VDW), respectively. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) were used to investigate the microstructures and components of the joints welded. The experimental results show that the FSKSW bonding method is a kind of compound mode that contains a mechanical connection and element diffusion fusion connection, in which mechanical connection has the main decisive function on joints of Mg/steel. Elements diffusion exists in the interfacial region of the joints and the elements diffusion extent is basically the same to that of VDW. The elements' diffusion in Mg/steel using FSKSW is defined in the reaction between small amounts elements of the base metal and zinc-coated metals. The intermetallic compounds and composite oxide perform some reinforcement on the mechanical connection strength.

A Review of Bonding Immiscible Mg/Steel Dissimilar Metals

“…Immiscible Mg/steel dissimilar metals can be bonded by this technology. The Zn coating is key to obtaining effective joints during most Mg/steel friction stir welding [10,11,12,13,14]. The purpose of Zn coating is to remove the oxide film and squeeze the new Zn phase to the edge, which could improve the weldability of Mg/steel.…”

“…ZEK100 Mg alloy and Zn coated DP600 steel was welded by refill FSSW and obtained 4.7 kN shear load [12]. AZ31B/galvanized mild steel joints were welded by friction stir keyholeless spot welding and obtained maximum shear strength of 8.7 kN [13]; the AZ31B/DP600 galvanized steel joints reached 8.7 kN [25] and 10.36 kN [11]. AZ31 Mg alloy and low carbon Zn coated steel joints obtained maximum failure loads of 2.3 kN [19] and 3.4 kN (65% of steel base metal) [18] by friction stir lap welding.…”

The Effect of Plug Rotation Speed on Micro-Structure of Nugget Zone of Friction Plug Repair Welding Joint for 6082 Aluminum Alloy

“…Therefore, FSW is recognized as an ideal welding method for aluminum alloy [ 2 ], which is widely used in aerospace, rail transportation and other fields [ 3 ]. Based on the plastic flow characteristics of materials in the FSW process, the joint can be divided into four zones: weld nugget zone (NZ), thermo-mechanical affected zone (TMAZ), heat affected zone (HAZ) and base metal zone (BM) [ 4 ]. Among these, the nugget zone is an “onion” ring structure [ 5 ] composed of uniform and finely equated grains, finer than those in other regions [ 6 ].…”

Recent Achievements in Rotary, Linear and Friction Stir Welding of Metals Alloys

“…In more detail, the contributions have concerned the following topics.The effect of cold rolling performed after friction stir welding (FSW) on the mechanical properties and formability of joints in AA5754-H114 aluminum alloy [1].The microstructure evolution of the welded joints of AA6082-T6 obtained using the bobbin friction stir welding process with a focus on grain refinement [2].The characteristic features of the entry and exit defects in the weld structure and formation mechanism of them during the BFSW process. The issue was investigated using stacked layers of multi-colored plasticine for the material flow detection [3].The thermo-structural analysis of material behavior, material flow, and defect generation during the friction stir butt-welding of 5083-O sheets [4].The characterization of the dissimilar friction stir weld of Ti-6242 S and Ti-54M in terms of microstructure, microhardness, fracture morphology, and material migrating from the retreating (RET) side to the advancing (ADV) one [5].The characterization of the interface of friction stir lap welding joints of 6082-T6 aluminum alloy and Q235A steel [6].The investigation of the microstructure evolution and properties response of a friction-stir-welded copper-chromium-zirconium alloy [7].The study of the influence of the process parameters on the vertical force generated during friction stir welding of AA6082-T6 aluminum alloy sheet blanks [8].The role of mechanical connection in friction stir keyholeless spot welding of AZ31B Mg alloy, Mg99.50, DP600, and non-zinc-coated DP600 lap welding [9].The application of a fully coupled thermo-mechanical model together with an enhanced friction law for the simulation of an FSW process with a cylindrical threaded pin tool [10].The identification of the chemical composition of etchant reagents for metallographic examination of the friction-stir welded A6082-T6 alloy [11].The study of an advanced meshfree computational framework to be used for the determination of optimal process parameters for the friction stir welding of an AA6061-T6 butt joint [12].The numerical modeling approach to the study of the linear friction welding of 30CrNiMo8 high strength steel Hero chain [13].…”

“…The role of mechanical connection in friction stir keyholeless spot welding of AZ31B Mg alloy, Mg99.50, DP600, and non-zinc-coated DP600 lap welding [9].…”