Friction stir welding/processing of metals and alloys: A comprehensive review on microstructural evolution

Friction stir welding (FSW), a highly efficient solid-state joining technique, has been termed as “green” technology due to its energy efficiency and environment friendliness. It is an enabling technology for joining metallic materials, in particular lightweight high-strength aluminum and magnesium alloys which were classified as unweldable by traditional fusion welding. It is thus considered to be the most significant development in the area of material joining over the past two decades. Friction stir processing (FSP) was later developed based on the basic principles of FSW. FSP has been proven to be an effective and versatile metal-working technique for modifying and fabricating metallic materials. FSW/FSP of aluminum alloys has prompted considerable scientific and technological interest since it has a potential for revolutionizing the manufacturing process in the aerospace, defense, marine, automotive, and railway industries. To promote widespread applications of FSW/FSP technology and ensure t...

Recent Advances in Friction Stir Welding/Processing of Aluminum Alloys: Microstructural Evolution and Mechanical Properties

In this paper, parameter optimization of FSW of cryorolled AA2219 alloy was carried out to obtain defect free weld joint with maximum weld strength. To achieve this, artificial neural network (ANN) was used to model the relationship between the input parameters and the mechanical and corrosion properties (output) of the weld joints. The optimal FSW parameters were determined by genetic algorithm (GA). The feasible solution of the GA was tool rotational speed of 1005 rpm, tool travel speed of 20 mm/min and tool tilt angle of 3°. The feasible parameter was used to weld and check the ability of the parameter to produce better weld joint than the L9 orthogonal array parameters. The weld, subjected to the confirmation test, was investigated by means of metallurgical, mechanical, and corrosion testing. This process reduces the costs associated with trial runs to obtain optimal parameters and also the production cost of the cryorolled (CR) plate which is high.

Parameter optimization of friction stir welding of cryorolled AA2219 alloy using artificial neural network modeling with genetic algorithm

Inhomogeneity of microstructure and mechanical properties in the nugget of friction stir welded thick 7075 aluminum alloy joints

Microstructural evolution and mechanical properties of the stir zone in friction stir processed AISI201 stainless steel

In this study, 20-mm-thick 7075-T6 aluminum alloy plates were joined by friction stir welding, and the temperature field, microstructure evolution, and mechanical properties of the joint along the thickness were investigated. The temperature profiles in different zones of the weld were measured by designing various thermocouple layouts. Fine dynamic recrystallized structures in the nugget zone (NZ) were observed, and different grain sizes were estimated by electron back scattering diffraction (EBSD) along the thickness. Also, the precipitate distributions and types in different locations were characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. Vickers microhardness was measured across different cross sections of the weld. Moreover, the results of tensile properties showed that the slice in the middle-upper had the highest ultimate tensile, yield strength, and elongation compared to other slices. Most of the failures for the joints presented a ductile fracture. All results were consistent with a temperature gradient along the thickness during friction stir welding (FSW).

Investigations on temperature distribution, microstructure evolution, and property variations along thickness in friction stir welded joints for thick AA7075-T6 plates

Five tools with different pin-tip profiles like thread taper, triangular, square, three grooves, and conical platform were designed to friction stir weld 20-mm-thick AA7075 alloy plates The effects of pin-tip profiles on thermal cycles, material flow, and mechanical properties of the joints were studied The results show that the temperature greatly decreases from the top to the bottom of the weld, and higher peak temperatures along the thickness are obtained using three grooves tool Due to poor plastic flow reflected by local transfer behavior of material, thread taper and conical platform tools yield macro cross-sectional level pore defect on advancing side in nugget zone However, triangular, square, and three grooves tools produce defect-free joints due to improving plastic flow resulted from stronger pulsating action and stirring power, leading to higher transfer displacements of local material The tensile test results show that the joints fabricated by three grooves tool have better mechanical properties including strength and ductility owing to better material flow A higher ultimate tensile strength of 391 ± 10 MPa, yield strength of 310 ± 12 MPa, and elongation of 83 % are obtained, respectively This can be attributed to finer grains, greater natural aging response and optimum hardness

Effect of tool pin-tip profiles on material flow and mechanical properties of friction stir welding thick AA7075-T6 alloy joints

The software of SYSWELD was used to build model and simulate the thermal cycle of in-service welding onto active pipeline of X70 steel using water as flowing medium.Influence of flow rate,pipe wall thickness and heat input on thermal cycle of coarse grain heat-affected zone was studied and the simulation results were tested by measuring thermal cycle on experiment pipelines.The results show that t_(8/5) decreases when flow rate increases but the decrease amplitude is not so obvious.When flow rate is less than 0.5 m/s,t_(8/3) and t_(8/1) rapidly decrease while flow rate increases.When flow rate is greater than 0.5 m/s,t_(8/3) and t_(8/1) decrease slowly while the flow rate increases.t_(8/5) and t_(8/3) increase with the pipe wall thickness increasing and arrive at the maximum when wall thickness is 8 mm,and then decreases.But t_(8/1) increases when wall thickness increases from 5 mm to 12 mm.t_(8/5),t_(8/3) and t_(8/1) increase with heat input increasing.The simulation results of the thermal cycle agree well with the measured results and the relative error is less than 8%.

Chen Yuhua

Papers

Investigations on temperature distribution, microstructure evolution, and property variations along thickness in friction stir welded joints for thick AA7075-T6 plates

Effect of tool pin-tip profiles on material flow and mechanical properties of friction stir welding thick AA7075-T6 alloy joints

Numerical simulation of thermal cycle of in-service welding onto active pipeline based on SYSWELD

Effect of Process Parameters on Mechanical Properties of Ti/Zn/Al Joint Welded by Friction Stir Welding