Friction Stir Joining Research Articles

Friction stir welding of pure magnesium and polypropylene in a lap-joint configuration: Microstructure and mechanical properties

A hybrid joint with a satisfactory mixture of pure magnesium and polypropylene (PP) was achieved via friction stir joining (FSW) in a lap-joint configuration. The tool rotational and travel speeds used in this work were 500–700 r/min and 50–100 mm/min, respectively. The mechanical properties and microstructural analysis of the resultant hybrid Mg/PP joint were examined. The results show that the maximum tensile shear strength (22.5 MPa) of the joint was attained at 700 r/min and 75 mm/min due to the optimum percentage fraction of mechanical interlocking (48%) and the presence of magnesium oxide. The interfacial joint center exhibits the maximum microhardness values because of the presence of refined and intertwined Mg fragments and density dislocations in the matrix of the PP. The joint failed via two different modes: interfacial line and weld zone fractures, respectively.

Friction Stir Spot Welding-Brazing of Al and Hot-Dip Aluminized Ti Alloy with Zn Interlayer

Friction stir spot welding (FSSW) of Al to Ti alloys has broad applications in the aerospace and automobile industries, while its narrow joining area limits the improvement of mechanical properties of the joint. In the current study, an Al-coating was prepared on Ti6Al4V alloy by hot-dipping prior to joining, then a Zn interlayer was used during friction stir joining of as-coated Ti alloy to the 2014-Al alloy in a lap configuration to introduce a brazing zone out of the stir zone to increase the joining area. The microstructure of the joint was investigated, and the joint strength was compared with the traditional FSSW joint to confirm the advantages of this new process. Because of the increase of the joining area, the maximum fracture load of such joint is 110% higher than that of the traditional FSSW joint under the same welding parameters. The fracture load of these joints depends on the joining width, including the width of solid-state bonding region in stir zone and brazing region out of stir zone.

Acoustic emission analysis for tool wear state during friction stir joining of SiCp/Al composite

As a key component of friction stir joining (FSJ), tools play an important role in welding quality and welding performance. In this study, the acoustic emission (AE) signal acquisition system was established. The AE signals from FSJ of SiCp/Al composites were analyzed in the time domain, frequency domain, and time-frequency domain respectively. The root mean square (RMS) value, spectrum distribution, and energy distribution of AE signals during FSJ were obtained. The relationship between the tool wear state and the AE signal was studied. The results show that with the increase of welding times, the wear degree of the pin is aggravating. The more serious the tool was worn, the greater the RMS value of the acoustic emission signal was. With the increase of wear, the energy of AE signals gradually moves to the low-frequency region, and the spectrum tends to be concentrated. According to wavelet packet decomposition of AE signals, it has been found that in the frequency bands 3–8, the energy percentage increases with the aggravation of agitation tool wear, while the opposite trend appears in the frequency bands 10–16.

Studies on Fractures of Friction Stir Welded Al Matrix SiC-B4C Reinforced Metal Composites

Studies pertaining to joining of Al alloy metal matrix composites reinforced with B4C and SiC by solid state friction stir welding (FSW) are presented in this paper. FSW tool dimensions are designed and fabricated to suit the weld sample dimensions and subsequently, the implications of the tool pin profile on the weldability is investigated. Through experimental recordings, the heat generated during the friction stir joining process of composites is estimated by developing relative equations. Maintaining the tool traverse speed constant, the rate of rotation and its effects on the tensile strength at the joints are investigated which reveals reduced ductility. The study emphasizes that when the speed is maintained between 100–400 mm/min, the tensile strength is at its optimal maximum while speeds higher or lower than the optimal range indicate detrimental effects on the tensile strength. This is followed by fracture studies on samples welding with varying traverse speed and rate of welding. Traverse speed appears to govern the fracture modes while brittle fracture is predominantly noticed indicating the importance of feeding optimal heat input during joining.

The Effect of Eccentricity of the Tool on the Surface Morphology of FSJ Joint

An attempt is made here to join 2024 aluminum alloy plate by friction stir joining (FSJ) using tools with different eccentricity. Joint surface morphology was observed, and the sizes of both arc line spacing and flash were measured. Furthermore, study the effect of eccentricity of the tool on the surface topography of FSJ joint and analyze the formation of the joint surface topography. It is found that, the space trajectory of long axis of shoulder which formed by the eccentricity of the tool determine the morphology of the arc lines; the ratio between the feed speed and the rotation speed determine the arc line spacing; length of time that long axis of shoulder squeeze the edge of the joint line in the advancing side and the retreating side determines the size of flash in both sides of the joint line. Arc lines were regularly distributed in the joint lines and there are also regular texture structure distributed in the flash of each side. The flash in the advancing side is less than the retreating side. Increasing the amount of eccentricity, it has litter effect on the arc line spacing but will destroy the arc lines morphology in the joint surface and promote the formation of filamentous flash structure in the both sides of the joint.

Analysis of the Main Factors Affecting the Surface Morphology of FSJ Joint

An attempt is made here to analyze the effect of the process parameter and shoulder of tool on the surface topography of FSJ (friction stir joining) joint. It is found that, it is a linear relationship between the feed speed and arc lines spacing, and the slope decreases as feed speed increasing. As the rotational speed increasing, the arc line spacing reduces. While FSJ processes completed at different parameters contain the same ratio between the feed speed and the rotation speed, the arc line spacing of the joint surfaces is the same. The shoulder of tool can increase the width of joint lines, refine arc lines structure, reduce the flash in the retreating side, but increase the flash in the advancing side.

Equipment Modification for Friction Stir Joining Based on PLC

In order to achieve the common drilling and milling machine for friction stir joining (FSJ) , A model ZXTM-40 equipment is modified., it’s workstation transmission mode and axial direction press mode are mechanical transmission, through the modification, install stepper motors and drives , write program code ,PLC control the motor ,it can work to achieve Longitudinal automatic movement . the speed of workstation can input through the Interactive panel, the control system operate parameters to achieve semi-automated operation of equipment and overtravel protection.. In the vertical direction,install a sleeve on the handle, the sleeve has scale and recesses, it can control the pressure measurement of friction stir pin. weights hanged on the sleeve, research proves the optimum parameters are 3KG weights and 40CM away from the center, Workbench moving speed of 125mm/min, rotation speed of 730r/min, it can join 1mm thick 2024 aluminum by FSJ, appearance of bead is good.

Study of friction stir joining of thin aluminium sheets in lap joint configuration

Thinning in friction stir lap joints and its relation with the process variables was investigated. Friction stir welds were made on 1 mm thick AA6111 aluminium alloy sheets in order to study the effects of rotation rate, traverse speed, plunge depth, tilt angle and pin height on faying surface defects. Sheet thinning on the advancing and retreating sides was quantified and the lap shear strength of the joints was evaluated. A decrease in the pitch of the runs at constant rotation rate increased the sheet thinning and reduced the joint strength in a linear manner. Process pitch and pin height were found to be the most critical factors in determining the faying surface lift up. A pin of the same height as the sheet thickness resulted in maximum lap shear strength. Tool tilt did not show a significant effect on the sheet thinning.