Submerged Friction Stir Welding Research Articles

Role of submerged friction stir welding in reducing intermetallic growth and enhancing microstructure in dissimilar Al-Ti joints

The integrity of dissimilar Al-Ti welds during conventional friction stir welding (CFSW) is compromised by excessive material mixing, leading to thick intermetallic layers. Underwater friction stir welding (UWFSW) mitigates these effects by inhibiting material mixing due to lower thermal conditions. Scanning electron microscopy revealed substantial Ti particles, appearing as blocks and strips, within the stir zone during CFSW. Static recrystallization, driven by exothermic reactions between Ti blocks and the Al matrix, resulted in over 93% recrystallized grains along stir zone, 10.7% higher than in UWFSW. In contrast, UWFSW resulted in a finer dispersion of Ti particles with reduced density due to lower frictional heat. The average grain size at the Ti interface of CFSW was 1.0 μm, compared to 2.6 μm in UWFSW. The inhomogeneous distribution of Ti particles in CFSW led to uneven dislocation distribution and increased stress concentrations, while finer Ti particles in UWFSW promoted a uniform grain structure, enhancing joint strength to 267 MPa, 13.4% higher than CFSW. Additionally, the γ-fibre and basal fibre texture in UWFSW increased joint ductility. The study highlights UWFSW’s effectiveness in joining dissimilar metals, offering significant advantages for industries such as aerospace and automotive.

Failure Analysis of Cu-DHP Joining Processes: A Comparative Study of FSW and SFSW Techniques

Abstract This article presents a failure analysis conducted on specimens extracted from 2.5 mm sheets of Cu-DHP (Cu99), which were joined using friction stir welding (FSW) and submerged friction stir welding (SFSW) processes. To evaluate the performance of the welded joints, destructive and non destructive tests, including tensile tests were performed. Additionally, morphologic analysis using scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) and fractography investigations were carried out on the samples. The results of experimental research show refined microstructures both for FSW and SFSW welding. Improved mechanical properties have been obtained for SFSW welding, compared to FSW. SFSW specimens demonstrates superior tensile strength and a higher hardness compared to FSW specimens, by performing joining process underwater. The fracture surfaces of the tensile test specimens from the base material (BM), FSW and SFSW joints, revealed the ductile fracture mechanism of the joints. EDX analysis confirms compositional integrity of the base and welded metals. Results highlights suitability of the FSW and SFSW processes for joining of copper Cu-DHP.

Investigation on submerged friction stir welding of AZ31B magnesium alloy under the influence of rotation speed

In this study, submerged friction stir welding (SFSW) was performed to weld 6 mm thick AZ31B Mg alloy plates, aiming to explore the impact of rotation speed on microstructure and tensile behavior. The water medium was used to submerge the samples. The SFSW was conducted at three different speeds (815, 960, and 1200 rpm), to assess the impact of rotation speed on SFSWed joint performance. As the rotation speed increased from 815 to 960 rpm, tensile strength increased plateauing over a range of the rotation speed. However, a significant drop in tensile strength occurred at 1200 rpm due to the formation of void defects. The SZ exhibits a size and width increment in the lower part with increasing rotation speed. The hardness of the stir zone (SZ) gradually rose with increasing rotation speed from 815 to 960 rpm. Fracture locations were observed in the thermal-mechanically affected zone (TMAZ) adjacent to the SZ at a rotation speed of 815 rpm, and in the heat-affected zone (HAZ) adjacent to the TMAZ at a rotation speed of 960 rpm. The joint welded at 1200 rpm fractured within the SZ. This study offers valuable insights into the welding and joining field, particularly regarding their mechanical characteristics.

Microstructure evolution and mechanical properties of Ti-15-3 alloy joint fabricated by submerged friction stir welding

Microstructure evolution and mechanical properties of Ti-15-3 alloy joint fabricated by submerged friction stir welding

Influence of Welding Tool Geometry on the SFSW Joint Dimensions of the EN AW 1200 Aluminium Alloy

The aim of the present paper is to study the aspects regarding the influence of the welding tool geometry on the joint dimensions during the SFSW (Submerged Friction-Stir Welding) of the EN AW 1200 aluminium alloy. Different tool geometries for SFSW welding of EN AW 1200 aluminium alloy parts were used, and joint size was analysed by macrostructural investigations. The key characteristics of the tool-weld interaction can be extracted, analysed and summarized to provide guidance on the optimal tool selection for a given set of welding conditions.

Improvement in tensile strength of Al/Cu dissimilar joints via submerged friction stir welding: revealing the action mechanism of water cooling on intermetallic compounds layer

Improvement in tensile strength of Al/Cu dissimilar joints via submerged friction stir welding: revealing the action mechanism of water cooling on intermetallic compounds layer

The Effect of Cooling Temperature on Microstructure and Mechanical Properties of Al 6061-T6 Aluminum Alloy during Submerged Friction Stir Welding

Submerged friction stir welding (SFSW) is a new modification of friction stir welding. In this paper, 6 mm thick 6061Al-T6 alloy plates were welded using the friction stir technique under normal air and submerged water conditions at 108 mm/min welding speeds and a rotational rate of 900 rpm. The cooling water temperature in SFSW varied at 0 °C, 35 °C, and 80 °C to clarify the effect of water temperature. The characteristic hourglass-shaped stir zone was observed in the macrostructure of all the samples. All the samples exhibited defect-free joints. The results revealed that the finer grain size of 2.43 μm was at 0 °C. The macrostructure of SFSW joints separated into the shoulder-driven zone and pin-driven zone due to the low-temperature difference between the environment and water media and the high heat absorption capacity of the water, which caused a more substantial cooling rate during water-submerged welded joints. The microhardness distribution of all the joints showed typical “W” shape characteristics. The microhardness for all submerged samples was higher than in normal air conditions due to the higher thermal cycling effect in submerged conditions. Improved dynamic recrystallization in the joint welded at 80 °C resulted in the highest tensile strength (~249 MPa) and microhardness (~95 HV).

EFFECTS OF SHOT PENNING ON MECHANICAL PROPERTIES, MICROSTRUCTURAL EVOLUTION AND RESIDUAL STRESS OF SUBMERGED FRICTION STIR-WELDED AA6061-T6 ALLOY

The purpose of this work is to study the effect of shot peening on the mechanical characteristics of welded plates which were performed by Submerged Friction Stir Welding (SFSW) on AA6061-T6 alloy. SFSW was carried out under three cooling mediums like water, brine solution, and coolant oil at the rotational speed of 1200[Formula: see text]rpm and welding speed of 45[Formula: see text]mm/min, respectively. The welded samples from each cooling medium were subjected to a shot peening process. A tensile test was carried out on weld peened and welds unpeened joints. The hardness of the various zones of HAZ, TMAZ, and NZ was also investigated. Optical and scanning electron microscopy was used to examine the microstructures of peened and unpeened joints formed by coolant samples. Shot peening has the potential to enhance the compressive residual stress of friction stir welded joints. According to these findings, shot peening had a greater impact on the mechanical properties of welded samples than unpeened samples, including tensile strength, percentage of elongation, and hardness. The grain size was a little bit smaller than the FSW sample because the surface of the welded samples was subjected to more strain during shot peening.

Effects Of Submerged Friction Stir Welding On Mechanical Properties Of AA6061 In Seawater

In this study, Al-Mg-Si alloy AA6061-T6 plates were joined in a seawater environment using the Submerged Friction Stir Welding (SFSW) technique, and process parameters were optimized using Taguchi L9 orthogonal arrays (OA). The parameters considered were tool rotational speed, tool transverse speed, and tool pin geometry. The MINITAB-17 software was used to analyze the responses using the signal-to-noise (S/N) ratio and analysis of variance (ANOVA). The optimum process parameters for tensile strength and joint Microhardness were determined. Furthermore, the ANOVA reveals that the tool rotational speed is the most important factor in determining joint mechanical properties such as UTS and Microhardness, with transverse speed and tool pin geometries coming in second and third. Experimental results confirm the effectiveness of this approach. The parent material microstructure and submerged stir welded samples were compared using metallographic scanning electron microscopy (SEM).

Achievement of high-strength Al/Cu dissimilar joint during submerged friction stir welding and its regulation mechanism of intermetallic compounds layer

The control of intermetallic compounds (IMCs) is the key to achieve high-performance Al/Cu dissimilar joints. In the present study, the dissimilar metals of 6061-T6 Al and T2 pure Cu were joined by submerged friction stir welding (SFSW) technology. The results indicated that the peak temperature and dwelling time at high temperature were obviously reduced by applying additional water cooling in SFSW. In comparison to the joint fabricated by normal friction stir welding (FSW), the thickness of IMCs layer at the interface for the SFSW joint was much thinner and its distribution was more uniform, the formation of IMCs was effectively inhibited during the SFSW process. The Al2Cu phase was first formed at the Al/Cu interface, and then Al4Cu9 phase precipitated between Al2Cu phase and Cu. The tensile properties of the Al/Cu joints were significantly improved by the SFSW process. The maximum tensile strength of 255 MPa was obtained in the SFSW joint, which was 41.7% higher than that of the FSW joint. A higher joint efficiency of 91.1% was reached, which was due to the reduced stress concentration at the interface in SFSW caused by the thinner IMCs layer and lower welding heat input. The fracture occurs within Al2Cu phase or along the interface between Al and Al2Cu layer for the FSW joint. In contrast, the SFSW joint fractures at the HAZ on Cu side, showing favorable ductility.

Simultaneously enhanced strength-ductility synergy and corrosion resistance in submerged friction stir welded super duplex stainless steel joint via creating ultrafine microstructure

In this paper, submerged friction stir welding (SFSW), capable of significantly weakening the welding thermal cycle compared to conventional FSW, was employed on SAF2507 super duplex stainless steel (SDSS). An ultrafine grained (UFG) dual-phase microstructure, characterized by more uniformly distributed and balanced alpha (α) and gamma (γ) phases with average grain sizes of 0.96 and 0.77 µm, respectively, was achieved in the stir zone (SZ). Such unique microstructure leads to a synergistic enhancement of tensile strength and ductility in the longitudinal SZ at room temperature, which increases from 840 MPa to 18% under AFSW condition to 915 MPa - 22%. As well, this UFG dual-phase microstructure plays a crucial role in determining the resultant higher corrosion resistance. Combining with the reduced width of entire joint, a transverse SFSW joint with a remarkable increased total elongation was successfully achieved. In addition, the relatively lower residual stress across the whole joint actually contributed to the increment of ductility in the SFSW joint, as compared to the traditional FSW joint. The aforementioned results demonstrate an effective strategy in achieving a completely balanced UFG microstructure across the whole SZ during SFSW and a concurrent improvement of strength, elongation and corrosion resistance.

Interface Formation of Medium-Thick AA6061 Al/AZ31B Mg Dissimilar Submerged Friction Stir Welding Joints.

The medium-thick Al/Mg dissimilar friction stir welding (FSW) joint has serious groove and cavity defects due to uneven thermal distribution in the thickness direction. The submerged friction stir welding (SFSW) was employed to decrease the peak temperature of the joint and control the thermal gradient of the thickness direction, which were beneficial in suppressing the coarsening of the intermetallic compounds (IMCs) layer and improving the weld formation. According to the SEM results, the thickness value of the IMC layer in the nugget zone and shoulder affect zone decreased from 0.78 μm and 1.31 μm in FSW process to 0.59 μm and 1.21 μm in SFSW process at the same parameter, respectively. Compared with the FSW process, SFSW improves the thermal accumulation during the process, which inhibits the formation of the IMCs and facilitates the material flow to form a mechanical interlocking structure. This firm interface formation elevates the effective contact area of the whole joint interface and provides a strong connection between the dissimilar metals. Thus, the ultimate strength of the 6 mm thick Al/Mg dissimilar SFSW joints was enhanced to 171 MPa, equivalent to 71.3% of AZ31B Mg alloys strength.

Achievement of High-Strength Al/Cu Dissimilar Joint During Submerged Friction Stir Welding and its Regulation Mechanism of Intermetallic Compounds Layer

Achievement of High-Strength Al/Cu Dissimilar Joint During Submerged Friction Stir Welding and its Regulation Mechanism of Intermetallic Compounds Layer

Effects of process parameters on mechanical and metallurgical properties of AA5083 weld bead and optimization by using Taguchi based grey relational analysis and ANOVA of submerged friction stir welding.

Friction stir welding (FSW) can be made to improve the mechanical properties in the weld zone. This article aims to obtain the optimum FSW process parameters used for two plates of AA5083 welded joints. The significant factors in the FSW process are tool rotational speed(TRS), tool transverse speed(TTS), and the weld process conditions are Submerged FSW and Normal FSW. For doing the investigation, the Taguchi method L18 orthogonal array design of experimentation is utilized. Using the Grey Relational Analysis(GRA) to calculate the grey relation grade, the response parameters are tensile strength, microhardness, and surface roughness. The Optimum process parameters contain been recognized, and ANOVA controls the significant contribution of process parameters. The optimal FSW process parameters are used to maximize the FSW joint strength. It is identified in the condition of Submerged FSW, high tool rotational speed, and low TTS.

Effects of friction stir welding on corrosion and mechanical properties of AA6063 in sea water

Submerged friction stir welding (FSW) is used to improve the weld zones mechanical properties in the present study. This research aims to obtain the optimized process parameters used to fabricate the AA6063 Submerged FSW joint. In the Submerged FSW process, the most important influential factors are tool rotational speed, traverse speed, and pin profile in a seawater environment. The different workpieces are friction stir welded while submerged in seawater at different tool rotational speeds, traverse speeds, and tool pin profiles such as square pin, cylindrical taper pin, and threaded pin. The produced weldments were tested for the mechanical properties of higher tensile strength, microhardness, corrosion rate, and the microstructure of weldments was characterized by using a scanning electron microscope, transmission electron microscope, and X-ray diffractometer. The corrosion rate is investigated by using an electrochemical analyzer by potential dynamic polarization open-circuit technique. For this investigation, The Taguchi method with the L9 orthogonal array design of experimentation is adopted. The maximum UTS was acquired in the weld joint fabricated with 1250 r/min of tool rotational speed, 45 mm/min traverse speed, and a square tool pin. The stirred zone is tested for microhardness. High hardness is achieved with high tool rotational speed and low traverse speed with a square tool pin profile. The corrosion rate is also decreased with high tool rotational speed, low traverse speed, and a square tool pin profile.

Numerical simulation and experimental investigation of subzero liquid SFSW of ME20M magnesium alloy

Subzero liquid submerged friction stir welding (SFSW) on Magnesium alloy is an investigate limited in the past. As an important lightweight alloy with enhanced yield strength and heat resistance, ME20M Mg alloy has potential value to be researched. In this paper, numerical and experimental subzero SFSW were carried out to systematically investigate the thermal histories, the microstructures and the mechanical properties. The solution of dry ice and ethanol was employed to be the cooling liquid, and different cooling temperatures were employed on low-temperature SFSW of ME20M Mg alloy. The results show that the simulated temperature curves and the experimental temperature curves are closed and within 5% error; as the increasing of the heat input, the precipitations reduced and grew up, the tensile strength of the joints first increased and then decreased, the microhardness of the weld joint decreased. The largest tensile strength is 165.8 MPa, about 69.08% of the base metal. The highest hardness was the peak hardness of the smallest ω/v in WNZ, the lowest hardness located at HAZ of the AS of the largest ω/v, and the values were 57.1 HV0.1 and 44.1 HV0.1, respectively.

Investigation of heat generation during submerged friction stir welding on 6061-T6 aluminum alloy

Friction stir welding (FSW) is a prominent solid state welding process that is widely used to obtain excellent joints in heat-treatable aluminum alloys. Submerged Friction Stir Welding (SFSW) is a new distinction of the popular friction stir welding. The aim of this paper is to study the heat generation (kJ) based on torque in submerged friction welding process on 6061-T6 aluminum alloy. Torque (M) is one of the most significant factors in friction stir welding process because it is directly related to the co-efficient of friction (µ), power (kW) and heat input of the process. In this work, friction stir welding was carried out on aluminium 6061-T6 alloy under normal and submerged conditions at the different rotational speeds (800 rpm, 1000 rpm and 1200 rpm). The water head is also differed from 10 to 20 mm in case of submerged friction stir welding process. Torque (Nm) was measured during the welding while the co-efficient of friction, power (W) and heat generation (kJ) were calculated later.

A Review on Submerged Friction Stir Welding of Light Weight Alloys

Friction stir welding gained wide acceptance in many industries owing to its capability of joining lightweight materials, the subsequent development to Friction stir welding (FSW) was to submerge workpiece in liquids during welding termed as submerged friction stir welding (SFSW) resulted in improving mechanical properties. However, joint efficiency was much dependent on the process parameters. Hence, the present work aimed to consolidate the research works available in underwater friction stir welding (UFSW) primarily focusing on effect of process parameters on weld joint.

Modeling and Optimization of the Yield Strength and Tensile Strength of Al7075 Butt Joint Produced by FSW and SFSW Using RSM and Desirability Function Method

Friction stir welding (FSW) is introduced as a solid-state welding process. Despite the many benefits of the FSW, the effects of the thermal cycles in this process are causing softening of the joint. This phenomenon generally occurs in heat-treatable aluminum alloys and results in reduced mechanical properties of the joint. To solve this limitation, submerged friction stir welding (SFSW) has been developed which is suitable for welding of heat-sensitive alloys. In this study, 31 butt joints were first produced from Al7075-T6 using the FSW. For this purpose, the response surface methodology was selected as the design of experiments method, and the variables: tool rotational speed, tool feed rate, tool shoulder diameter, and tool tilt angle were determined as the input variables. Then, the statistical analysis of the parameters affecting the yield strength and tensile strength of the joints was investigated. Then, 10 joints were produced using the SFSW based on the optimal values of the tool feed rate and tool tilt angle. Results of the ANOVA and regression analysis of the experimental data confirmed the accuracy and precision of regression equations and showed that the linear, interactional and quadratic terms of tool shoulder diameter and tool rotational speed effect on the yield strength and ultimate tensile strength of submerged joints. Also, the optimal conditions of input variables were determined by the desirability method and confirmed by the verification test.

Optimisation of submerged friction stir welding parameters of aluminium alloy using RSM and GRA

ABSTRACT Friction Stir Welding (FSW) uses friction and mechanical plastic deformation to heat and soften any weld material, allowing mechanical deformation comparable to extrusion and forging for enabling the formation of a highly strengthened joint. This paper reports the use of response surface methodology-based grey methods for the optimisation of the Submerged Friction Stir Welding (SFSW) process parameters, as joining the 6061-T6 aluminium alloy. The process parameters selected were the rotational speed (rpm), welding speed (mm/min) and water head (mm). Experiments were carried out on aluminium alloy using a servo controller FSW machine. The mechanical properties (average hardness and % of elongation) of submerged friction stir welded joints of the 6061-T6 aluminium alloy were investigated. The optimal welding process parameters for maximising the Avg.hardness and % of elongation were identified using the Grey Relation Analysis (GRA). Quadratic equation was developed for predicting the grey relational grade with good accuracy and fitted with adequate errors. The analysis of variance (ANOVA) was for testing to test the significance of the equation. The microstructural characteristics of the base metal and welded zone, as well as grain structure, were studied using scanning electron microscopy.