Study on influence of tool shape on stirring performance and wear during FSW using numerical simulation

Dissimilar friction stir welding between steels with different carbon contents was carried out by placing the parent materials at two different fixed locations: the advancing side (AS) and the retreating side (RS). The phase transformation and the depth and width of the weld were affected by the fixed location. A smaller weld nugget was formed, and more martensite transformation occurred when the stronger SK5 steel was fixed at AS, compared to that at RS. This variation was attributed to the difference of temperature and materials flow between AS and RS.

The aim of this research is to use a full factorial design to determine the significant factors of friction stir welding (FSW) process of dissimilar AA6061-T6 and AA7075-T651 aluminum alloys, on the surface residual stress and microhardness. There are a total of three factors studied: rotation speed, welding speed and workpiece layout. The results showed that the factors that have a statistically significant effect on residual stress occurring are welding speed, workpiece layout and interaction between rotation speed and welding speed. The appropriate parameters for FSW process of dissimilar aluminum alloys are rotation speed of 1400 rpm, welding speed of 50 mm/min and the layout of the workpiece by advancing side (AS) uses AA6061-T6 sheet, while retreating side (RS) uses AA7075-T651 sheet, which will result in the surface residual stress of −34.33 MPa. This compressive residual stress will be beneficial to the welded joint for retard the occurrence of cracks caused by fatigue. The hardness of all workpieces have similar tendency, thermo-mechanically affected zone (TMAZ) area in both AS and RS gave the least hardness, which found that the AA6061-T6 and AA7075-T651 sheets had a hardness of approximately 55HV and 110HV respectively.

Effect of welding speeds on the metallurgical and mechanical property characterization of friction stir welding between dissimilar aerospace grade 7050 T7651-2014A T6 aluminium alloys

Influence of welding speed on microstructure formation in friction-stir-welded 304 austenitic stainless steels

On the microstructure and mechanical properties of similar and dissimilar AA7075 and AA2024 friction stir welding joints: Effect of rotational speed

A 6.5 mm thick aluminum(base) / copper(clad) laminated composite joint was successfully fabricated via friction stir welding (FSW), with the material mixing behavior at the aluminum(Al) / copper(Cu) interface systematically investigated using the Coupled Euler-Lagrange (CEL) method. Molecular dynamics (MD) simulations were employed to elucidate the diffusion mechanisms of intermetallic compounds (IMCs) on the retreating side (RS). Results show that, at a constant welding speed of 150 mm/min, increasing rotational speed enhances Cu concentration near the weld center with pronounced dissimilar metal migration. The RS exhibits less variation in volume fraction profile compared to the advancing side (AS), accompanied by expansion of the Al/Cu stir zone. Maintaining rotational speed at 900 rpm, elevated welding speeds reduce heat generation, leading to insufficient metal plasticization and void formation in the stir zone. Insufficient heat input at 300 mm/min causes severe interface damage, as evidenced by significant fluctuations in the volume fraction curve. MD analysis reveals that elevated temperature at RS promotes atomic interdiffusion at the Al/Cu interface, where Cu demonstrates higher diffusivity in Al lattice than vice versa, attributed to lattice constant mismatch and dissolution enthalpy difference. First-neighbor hopping is identified as the predominant diffusion mechanism for Cu atoms, with shear rate increase further accelerating interfacial diffusion. Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)-assisted X-ray diffraction (XRD) analysis confirms that excessive IMC growth (primarily Al₂Cu and Al4Cu9 phases) under high heat input induces a heterogeneous thickness distribution and reduces joint integrity.

Study on in-situ material flow behaviour during friction stir welding via a novel material tracing technology

The effect of friction stir welding (FSW) parameters on the microstructure and mechanical properties of 5.6 mm thick 2219Al-T6 joints was investigated in detail. While the sound FSW joints could be obtained under lower rotation rates of 400–800 rpm and welding speeds of 100–800 mm/min; higher rotation rates of 1200–1600 rpm easily led to the tunnel and void defects. The FSW thermal cycle resulted in low hardness zones (LHZs) on both retreating side (RS) and advancing side (AS). The LHZs may be located at the interface between the nugget zone (NZ) and the thermo-mechanically affected zone (TMAZ), at the TMAZ, or at the heat affected zone under the varied welding parameters. The tensile strength of FSW 2219Al-T6 joints increased when increasing the welding speed from 100 to 800 mm/min, and was weakly dependent on the rotation rates from 400 to 1200 rpm. The FSW 2219Al-T6 joints fractured along the LHZ on the RS.

Influence of material position and tool axis offset on the stir zone material flow and joint integrity of friction stir welded dissimilar AA5083 and AA7050 alloys

In current research work, an attempt has been made to join dissimilar metals by employing friction stir welding (FSW), i.e., AA3003-H12 (aluminium alloy) and C12200-H01 (copper alloy). The experiments are designed as per full factorial design at different process parameters, namely tool pin profiles, rotational speed, welding speed, and shoulder diameter while the ultimate tensile strength (UTS), yield strength (YS), and percentage elongation (% E) are considered as a performance parameter. Moreover, a statistical tool, i.e., analysis of variance (ANOVA) is also utilized to check the adequacy of the results. It is observed that the higher UTS, % E and YS are obtained by employing a taper pin profile tool at a rotational speed of 1800 rpm, a welding speed of 16 mm/min, and a shoulder diameter of 22.5 mm. The ANOVA results showed that the rotational speed is the most significant factor for current research work. In addition, a scanning electron microscope is utilized for microstructural analysis of welded joints. It is witnessed that the minimum grain size, i.e., 4 microns, is obtained for highest strength specimen and the maximum grain size is obtained for the lowest strength specimen i.e., 31 microns. Besides this, the swirling of cu particle is also observed from advancing side (AS) to the retreating side (RS). Moreover, energy-dispersive X-ray spectroscopy (EDS) indicates the formation of intermetallic compounds i.e. Al2Cu, Al9Cu4 at nugget zone (NZ). The hardness is found to be higher at NZ due to the presence of Al-Cu intermetallic.

Friction stir welding (FSW) was performed on thick plates of high-strength low-alloy (HSLA) steel with polycrystalline cubic boron nitride (PCBN) tools. To investigate the mechanism of microstructure formation in the stir zone (SZ), the prior austenite structure undergone through a thermo-mechanical history during the FSW process was investigated. The prior austenite structure was reconstructed by the local crystal orientations of prior austenite calculated from the bainite orientations by using the Kurdjumov–Sachs orientation relationship between the prior austenite and bainite. The reconstructed austenite revealed a heterogeneity in the SZ. The austenite grain size in the advancing side (AS) of SZ was larger than that of the retreating side (RS). Thus, a reheated temperature of AS was considered to be higher than that of RS. The textures of reconstructed austenite were also different in SZ. The rolling texture was observed in RS, but the shear texture was observed in the centre and AS. The heterogeneous microstructure and texture in SZ was considered to be caused by the material flow behaviour in FSW process.

During dissimilar friction stir welding (FSW) of Al-Mg2Si metal matrix composite and AA6061 aluminum alloy, the temperature field and heat generation were investigated using a 3-dimensional computational fluid dynamics (CFD) model and FLUENT software. The simulations were conducted for rotational speeds of 720, 920, and 1120 rpm. The welding experiments were carried out to validate the simulation results. About 70% of the heat is generated at the interface between the shoulder and the workpiece. The maximum temperature is predicted on the advancing side (AS). The difference between the peak temperatures on the AS and the retreating side (RS) is about 115 K. The effect of the rotational speed on the peak temperature is significant. The temperature distribution in the cross sections is asymmetric, which originates from different material velocities on the AS and RS. The peak temperature on the RS develops under the top surface, while the peak temperature on the AS develops on the surface.

The dissimilar welding of titanium and copper by fusion welding is very difficult because the melting points of the materials are very highly different and strong brittle intermetallic compounds (IMCs) can be easily produced in welded zone and heat-affected zone, etc. Friction stir welding was employed as a type of solid-state welding for Ti/Cu dissimilar welding to obtain a sound welded zone and reduce the total process cost. This study investigated how the metal flow of the welded zone changes according to the variation in the rotational speed of the tool, from 450 rpm to 600 rpm. When the rotational speed was too high, the plastic flow of the softened material increased and intermetallic compounds such as TiCu, Ti2Cu3, and Ti2Cu, were generated in the Cu region of the welded zone. The microstructural evolution of AS (Advancing Side) and RS (Retreating Side) were investigated and the soundness of the welded zone and its mechanical properties were evaluated through the microstructural evolution. A high hardness value of 200 Hv or more was exhibited in some points, due to the formation of intermetallic compounds in the RS (Cu) region. Ti/Cu dissimilar friction stir welding at a welding speed of 50 mm/min and an appropriate rotation speed of 500 rpm showed a good welded zone and mechanical properties.

Regulating the microstructure and strength of the advancing side interface zone in AZ31 friction stir welded joint via localized selective remelting

The usage of Friction Stir Welding(FSW) technology has been increasing in order to reduce the weight in automobile industries. Previous studies that investigated on the FSW have focused on the aluminum alloy. In this study, Al6061-T6 alloy plates having 5 mm of thickness were welded under nine different conditions from three tool rotation speeds: 900, 1000 and 1100 rpm, and three feed rates: 270, 300 and 330 mm/min. Specimen size of Micro Shear Punch(MSP) test was <TEX>$10{\times}10{\times}0.5mm$</TEX>. The mechanical properties were evaluated by MSP test and Analysis of Variance (ANOVA). The specimens were classified by advancing side(AS), retreating side(RS), and center(C) of width of tool shoulder. The optimal welding condition of FSW based on micro strengh was obtained when the tool rotation speed was 1100 rpm and the feed rate was 300 mm/min. The maximum load measured AS, RS, and C in the weldment was measured 554.7 N, 642.9 N, and 579.2 N, respectively.