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Three types of pinless friction stir spot welding (PFSSW) tools were designed employing Fibonacci spiral curve, involute curve, and Archimedean spiral curve to create corresponding grooves. Subsequently, PFSSW experiments were conducted on copper sheets using these three distinct tools. The surface morphology, cross-sectional macrostructure and microstructure, microhardness, joint strength, fracture type, and fracture surface morphology of the joints were analyzed under the influence of different tools. The research findings indicate that the Fibonacci spiral curve groove (FSCG) tool exhibits the highest disparity in three-dimensional morphology within the central zone of the joint, followed by the involute curve groove (ICG) tool and the Archimedean spiral curve groove (ASCG) tool. The ICG tool generates the widest stirring zone (SZ) in the joint, while the FSCG tool produces the deepest SZ. The grains of SZ under all three tools is coarser compared to the base material. The microhardness values under the ASCG tool are relatively higher, whereas those under the FSCG tool are lower. Among the welded specimens, those created using the FSCG tool exhibit the highest average tensile-shear failure load of 8.21 kN, followed by the ICG tool of 7.80 kN, and the ASCG tool yielding the lowest average tensile-shear failure load of 7.77 kN. The fracture type of the specimens welded by FSCG tool is semi-nugget pull-out fracture, while the joint specimens of ICG tool and ASCG tool are both nugget pull-out fracture. The fracture mode of the joints under all three tools is characterized as ductile fracture. The conducted research can not only enrich the variety of PFSSW tool grooves, but also enhance the comprehension of joint properties under distinct tool groove configurations. [ABSTRACT FROM AUTHOR]

The friction stir welding (FSW) of 6010-T6 aluminum alloy sheet with 10 mm thickness was carried out with tool tilt angle of 0°. The process parameters that could realize effective joint were given. The performance of the weld zone was tested. The experimental results showed that the effective FSW could be achieved under the process parameters of rotation speed of 400–600 rpm and welding speed of 200–400 mm/min. The tensile strength of the weld zone was the best under the rotation speed of 600 rpm and welding speed of 400 mm/min, which was 86.4% of the base metal, under which process the microhardness of the nugget zone was higher than that under other processes, and the grain was significantly finer than that of the base metal zone. This paper presents the technological breakthrough of the FSW of 10 mm thickness aluminum alloy with tool tilt angle of 0°. [ABSTRACT FROM AUTHOR]

Welding of 10 mm thick AZ31B magnesium alloy by stir friction welding technique. The effects of process parameters on the microstructure, tensile strength and impact resistance of the joints were analyzed. The results showed that the joints were formed with good quality and no obvious defects, and the joints were fine-grained and accompanied by grain dislocations. The grain dislocation in the hot machine influence zone is more obvious there is a dense grain dislocation zone, and the distribution is not uniform. When the spindle speed is 800 and 1000 rpm, respectively, the best impact resistance of the welded joint impact work is 8.02 J, which is about 94.2% of the impact resistance of AZ31B magnesium alloy base material. When the spindle speed is 1000r/min and the welding speed is 150 mm/min, the tensile strength of the welded joint is the largest, reaching 85.8% of the base material and the post-break elongation is 1.9 times that of the base material. Thick plate magnesium alloy plate welded joints overall performance is not uniform, welded plate bottom mechanical properties of the worst, weld core area doped magnesium alloy oxide, joint tensile fracture crack source from the bottom of the plate to the weld surface expansion. [ABSTRACT FROM AUTHOR]

The article adopts S-Type track friction stir joining to butt joining of 10 mm thick 6061-T6 aluminum alloy, and conducts impact toughness test and 24h salt spray corrosion on the joint area. On the premise of ensuring the tensile strength, by changing the swing radius of different S-shaped trajectories, and comparing with the conventional linear joining trajectory, it is obtained that at a speed of 500r/min, a joining equivalent speed of 130 mm/min, and a swing radius of 0.5 mm Under the parameters, the maximum impact toughness is 80.74 J/mm2, and the corrosion resistance is better than the base material and the straight joining track. The S-shaped trajectory of friction stir joining area with a swing radius of 0.5 mm forms a "thousand-layer cake" structure with high bonding strength, which can effectively improve the impact resistance and corrosion resistance of the joining area. [ABSTRACT FROM AUTHOR]

The 10 mm thick 7075-T6 aluminum alloy plate is welded by friction stir welding with the inclination of the main shaft of 0.5°. There is no obvious thinning on the weld surface, and the welded joint is well formed. The microstructure of the joint as a whole is "funnel" shaped, and there are multi gradient flat "onion rings". The grains in the weld nugget zone are equiaxed and the grains are significantly refined, and the grains in the heat-mechanical affected zone appear mixed crystal phenomenon and have obvious deformation. During the welding process, the hardness of the welded joint is reduced due to high temperature annealing. When the spindle speed is 500 rpm and the welding speed is 120 mm/min, the maximum surface hardness of the welded joint is 178.77HV. Compared with the base metal after annealing, the hardness of the weld nugget area is increased by about 25% due to the grain refinement strengthening and the precipitation of the reinforcing phase. The wear resistance of welded joints is inversely proportional to the hardness. When the spindle speed is 300 rpm and the feed speed is 120 mm/min, the wear resistance is the best. The friction type is mainly adhesive wear, supplemented by particle wear and fatigue wear. [ABSTRACT FROM AUTHOR]

Four tool plunging paths including a one-time plunging path and three step-by-step plunging paths were designed to study the effects of the tool plunging path on the welded joint properties of pinless friction stir spot welding (PFSSW). The appearance, cross-sectional microstructure, welding temperature, microhardness, and tensile shear failure load of the PFSSW of thin copper sheets under different tool plunging paths were explored. Furthermore, the fracture modes of welded joints under different tool plunging paths were analyzed. Studies showed that path 1 (plunge total depth at one time) produced the largest range of stirring zone, but the grains in the stirring zone were larger and the width of the thermal-mechanical affected zone was smaller. Path 1 obtained the highest peak temperature during the welding process, and path 3 (plunge 1/3 total depth + plunge 2/3 total depth) gained the lowest peak temperature. The greater the initial plunging amount of the tool, the faster the temperature rise rate in the welding stage. The tensile shear failure loads for path 1, path 2 (plunge 1/2 total depth + plunge 1/2 total depth), path 3, and path 4 (plunge 2/3 total depth + plunge 1/3 total depth) were 8.65 kN, 8.15 kN, 8.25 kN, and 8.85 kN, respectively. The tensile shear failure load of path 4 was 2.3% higher than that of path 1. The fracture modes of welded joints under different tool plunging paths were all nugget pullout fractures. The fracture morphology indicated that the fracture type was ductile fracture. The step-by-step plunging path proposed in this work extends the traditional PFSSW process. The findings of this study can provide a reference for the selection and design of tool plunging paths for PFSSW. [ABSTRACT FROM AUTHOR]

The state of the simulation technology widely used in friction stir welding (FSW) studies requires greater and greater accuracy. An analysis is made of an FSW dynamic heat source model and related information. The model is combined with results from FSW experiments and the welding temperature field. A relationship is obtained for the friction coefficient between the tool and welding materials with temperature. By incorporating tool force measurements and analysis, a simulation model which is much more in line with actual FSW results is thus established. In the simulation process, the temperature of each part of the tool, the material model, fixture constraints, and the role of tool–material forces are analyzed and discussed in detail. In the new model, the different input heats on the advancing and retreating sides on the shoulder, the pin surround, and top of the pin are distinguished. The mechanical properties of the materials with change in temperature and the constitutive equations for the welding, before and after, are obtained. The contact relationship between the fixture and workpiece was built. In the welding process, the forces of the tool toward the welding material were applied. The 7022 aluminum alloy FSW process was simulated by the constructed simulation model. The temperature field, residual stress, and deformation in the simulations were in good agreement with the experiment results. [ABSTRACT FROM AUTHOR]

The present research envisaged the performance analysis of a 1-mm thick 6061-T6 aluminum alloy sheet welded by the friction stir welding technique, using optical microscopy, micro-hardness measurement, a tensile test, a friction and wear test, and a salt spray corrosion test. It was found that the grain in the welded zone obtained was refined under each parameter. When the rotating speed of the tool was 15,000 rpm and the traveling speed of the tool was 300 mm·min-1, the tensile strength of the welded zone was highest, i.e. 74.8% of the base metal. Furthermore, the hardness distribution curve of the welded zone was of the 'W' type under each parameter, but the hardness value was lower than that of the base metal. The friction coefficient of the welded zone was lower than that of the base metal under each parameter, and the wear form was found to be mainly adhesive wear accompanied by abrasive wear. The welded zone and the base metal were subjected to salt spray corrosion after 12 hours under each parameter, which had a negative effect on the quality. However, after 12 hours of subsequent corrosion, the quality of each sample and the base material was not obvious. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]