Properties Of Friction Stir Welding Research Articles

Microstructures and mechanical properties of friction stir welds on 9% Cr reduced activation ferritic/martensitic steel

In this study, the microstructures and mechanical properties of 9%Cr reduced activation ferritic/martensitic (RAFM) steel friction stir welded joints were investigated. When a W-Re tool is used, the recommended welding parameters are 300rpm rotational speed, 60mm/min welding speed and 10kn axial force. In stir zone (SZ), austenite dynamic recrystallization induced by plastic deformation and the high cooling rates lead to an obvious refinement of prior austenite grains and martensite laths. The microstructure in SZ contains lath martensite with high dislocation density, a lot of nano-sized MX and M3C phase particles, but almost no M23C6 precipitates. In thermal mechanically affect zone (TMAZ) and heat affect zone (HAZ), refinement of prior austenite and martensitic laths and partial dissolution of M23C6 precipitates are obtained at relatively low rotational speed. However, with the increase of heat input, coarsening of martensitic laths, prior austenite grains, and complete dissolution of M23C6 precipitates are achieved. Impact toughness of SZ at −20°C is slightly lower than that of base material (BM), and exhibits a decreasing trend with the increase of rotational speed.

Effect of post weld artificial aging on the local and global mechanical properties of friction stir welds of aluminum alloy 6061-T6

The aim of this work is to study the responses to post weld artificial aging (PWAA) of friction stir welds of aluminum alloy 6061-T6 welded at low traverse speed of 125 mm/min and at high traverse speed of 710 mm/min. During welding of either the low traverse speed or high traverse speed weld, the transverse profile of peak temperatures and the local thermal cycles at various distances from the weld center were measured. The transverse hardness profile of the low traverse speed and high traverse speed weld were measured one day after welding and after PWAA. Both immediately after welding and after PWAA the transverse profiles of tensile properties, and strain hardening parameters were determined. Special attention was given to the local properties within the weld weakest region, which greatly affect the overall strength and ductility of the welded joints. The results show that PWAA greatly improve the tensile properties of the high traverse speed weld. For the low traverse speed weld, while PWAA slightly improves yield and ultimate tensile strength, it deteriorates the uniform elongation due to the severe mismatch in local mechanical properties between the various zones of the weld.

The Simulation of Precipitation Evolutions and Mechanical Properties in Friction Stir Welding with Post-Weld Heat Treatments

A finite element model of friction stir welding capable of re-meshing is used to simulate the temperature variations. Re-meshing of the finite element model is used to maintain a fine mesh resolvin ...

Effects of preheating treatment on temperature distribution and material flow of aluminum alloy and steel friction stir welds

Material flow and temperature distribution during welding are important factors that affect the properties of friction stir welding (FSW) joints. The scope of this investigation is to evaluate the effect of preheating treatment on the temperature distribution and material flow of aluminum alloy and steel joints produced by FSW. In this investigation, the finite volume model of butt FSW was established on basis of the FLUENT software. The flow of material during the FSW was simulated, and the temperature distribution in the FSW process was obtained by experiment and simulation. The effects of preheating treatment on the thermal history, temperature distribution, and material flow during FSW were elucidated in detail. The effects of preheating on the tensile strength and failure modes of the specimens were also discussed. The simulation shows that the preheating treatment increased the peak temperature of the steel, and also reduced the large temperature difference between the steel and the aluminum alloy in the high temperature stage. Simulation results, including temperature distribution and thermal history, were corresponded with the experimental results. The preheating treatment improved the flow velocities of the plastic materials and reduced the difference in flow velocities of the two materials. The preheating treatment could reduce the influence of the difference between the two materials on the forming of the welded joint and improve the property of the welded joint.

Microstructure and mechanical properties of friction stir welds on unmodified and P-modified Al-Mg2Si-Si alloys

Welded joints formed by friction stir welding (FSW) consist of three distinct zones: a base material zone (BMZ), a thermo-mechanically affected zone (TMAZ), and a weld nugget (WN). Primary Mg2Si phases are identified as equiaxed crystals and polygonal particles in unmodified and P-modified Al-Mg2Si-Si alloys in the BMZ, respectively. In the WN, the equiaxed primary Mg2Si crystals in the unmodified alloys are transformed to significantly smaller polygonal/irregular particles; the corners of the polygonal primary Mg2Si particles in the modified alloys become smoother and smaller. The segregation of the primary Mg2Si phase is reduced for both the unmodified and modified alloys in the WN. Both unmodified and modified alloys have a lower solidus temperature in the WN. The ultimate tensile strengths (UTSs) of the welded joints are enhanced by 5% and 8% for the unmodified and modified alloys, respectively, in comparison with the parent material. The UTS of the welded joints in the modified alloy is ∼20% higher than in the unmodified alloy.

Process responses and resultant joint properties of friction stir welding of dissimilar 5083 and 6061aluminum alloys

The effects of combinations of dissimilar aluminum alloys during Friction stir welding (FSW) on the process response and resultant joint properties are experimentally investigated using two dissimilar automotive structural aluminum alloys. Depending on the materials on the advancing and retreating sides of the tool travel direction during FSW, four different material combinations are considered. FSW joints without macroscopic defects are successfully fabricated for the four different material combinations. The optical microscopy results show that the macroscopic material mixing behaviors of the two dissimilar material combinations during FSW are somewhat different from each other, even though the process responses during joining are not much different. The results of the quasi-static tensile tests and EBSD analysis demonstrate that the mechanical behaviors and orientation changes of the joint during tensile deformation are affected by the material locations with respect to the tool travel direction during FSW.

Microstructural developments and mechanical properties of friction stir welding of AZ91D magnesium alloy plates

Friction stir welding (FSW) is an efficient technique which can be used particularly for magnesium and aluminum alloys that are difficult to fusion weld. In this work AZ91D Mg alloy plates 3mm thick were friction stir welded at different process variables such as rotational speed and welding speed. The range of rotational speeds varied from 1025 to 1525 rpm, and the welding speed varied from 25 to 75 mm/min. Good quality welds were obtained under 1025 rpm of rotational speed with the welding speeds range from 25 to 75 mm/min. The microstructure of the AZ91D alloy consists of primary α-phase, eutectic α-phase and eutectic β (Mg17Al12) phase in the received condition (gravity die cast). The original dendrite grain structure completely disappeared and was transformed to fine equiaxed grains in stir zone (SZ). It was observed that there was a slight increase in hardness in SZ, because of fine recrystallized grain structure. The transverse tensile test results of weld specimens indicated constant strength irrespective of traveling speed. Fractrographic analysis of the friction stir welded specimens showed the brittle failure.

Multi-Objective Optimization of Friction Stir Welding Process Parameters of AA6061-T6 and AA7075-T6 Using a Biogeography Based Optimization Algorithm.

The development of Friction Stir Welding (FSW) has provided an alternative approach for producing high-quality welds, in a fast and reliable manner. This study focuses on the mechanical properties of the dissimilar friction stir welding of AA6061-T6 and AA7075-T6 aluminum alloys. The FSW process parameters such as tool rotational speed, tool traverse speed, tilt angle, and tool offset influence the mechanical properties of the friction stir welded joints significantly. A mathematical regression model is developed to determine the empirical relationship between the FSW process parameters and mechanical properties, and the results are validated. In order to obtain the optimal values of process parameters that simultaneously optimize the ultimate tensile strength, elongation, and minimum hardness in the heat affected zone (HAZ), a metaheuristic, multi objective algorithm based on biogeography based optimization is proposed. The Pareto optimal frontiers for triple and dual objective functions are obtained and the best optimal solution is selected through using two different decision making techniques, technique for order of preference by similarity to ideal solution (TOPSIS) and Shannon’s entropy.

Fatigue modeling and life prediction for friction stir welded joint based on microstructure and mechanical characterization

Fatigue properties of friction stir welding (FSW) butt joints for aluminum alloy AA2219 were researched by experimental analysis and numerical simulation. The FSW joint model including the representative volume elements (RVE) was built based on the metallographic morphologies, micro hardness profile and local mechanical properties. The morphology and distribution of the matrix and precipitation strengthening phases were included in the RVE of the joint. The stresses and plastic strains of the precipitation strengthening phases and matrix were estimated with the mixture rules. Stress concentration happens at the strengthening phases and neighbouring metal matrix. Plastic strain concentration appears at the interface of the matrix and strengthening phases. The fatigue weak areas in the FSW joint were obtained with the joint model. The results show that the estimated fatigue weak areas are close to the experimental results and the errors of predicted fatigue life are basically within 2 factors based on the FSW joint model.

Mechanical properties of friction stir welding and metal inert gas welding of Al-Zn aluminum alloy joints

In this work, an Al-Zn aluminum alloy was welded using friction stir welding (FSW) and metal inert gas (MIG) welding methods. The comparison between microstructure and mechanical properties of the two different joints was mainly discussed. Results showed that defect-free joints can be obtained using both the two welding methods. Due to much less heat input, grains of the stir zone (SZ) of the FSW joint are finer than those of the MIG joint, resulting into higher hardness. Tensile strength of the MIG and FSW joints respectively reaches 68.6 and 73.2% of the BM. The FSW joints own much better fatigue properties than the MIG joints and reach its infinite life at using 90 MPa. The FSW joint owns two cracks during the fatigue test.

Mechanical and structural properties of friction stir weld of dissimilar aluminum alloys

In this work, the structural and mechanical properties of friction stir welded dissimilar butt joints of AA2024-T351 to AA5083-H112 aluminum alloys were evaluated. Plates of 6 mm thick were friction stir welded with optimized tool. In the first case, plate of AA2024 was positioned on the advancing and plate of AA5083 was on the retreating side of the weld. In second case, position of the plate was opposite. Specimens were welded using rotation rate of 750 rpm and welding speed of 73 and 93 mm/min. Specimens were defect free, with good or acceptable weld surface. The effects of rotation and lateral speed of the welding tool were related to structural features and mechanical properties. The structural appearances of concentric rings in the nugget zone were controlled by tool speed and plate position. Structural analysis of the joint cross-section, revealed the distinct lamellar bands. The joints consistently failed on the AA5083 aluminum alloy plate. Failures were observed through the heat-affected zone at distance of approximately 21 mm from weld center.

Evaluation of heat input during friction stir welding of aluminium alloys

Heat input is one of the key parameters governing the quality and service properties of friction stir welds. By using a calorimetric technique, the heat inputs generated during the friction stir welding of the aluminium alloys, 1100 and 5083, were measured over a wide range of welding parameters. An empirical equation to estimate the heat input using the welding parameters was established based on a multiple regression analysis of the results. The effect of the heat input on the final grain size of the stir zone was also investigated by the electron backscatter diffraction method. The quantitative relationships between the input variables, heat inputs, and final grain sizes in the stir zone were derived.

Force response characteristics and mechanical properties of friction stir welded AA2024 sheets

Process force and tensile properties in friction stir welding of AA2024 sheets were studied. Results show that the forces present a periodic variation with the same periodicity which is nearly equal to the time of one tool rotation, and thus it only depends on rotation speed. With increasing welding speed the forces increase gradually, while with increasing rotation speed the forces first decrease and then increase. Joints with superior strength-ductility synergy are produced at 900 rev min−1–300 mm min−1 and 1000 rev min−1–350 mm min−1. These joints experience nearly the same peak temperature and axial force. As heat input increases the failure initiates from the interface between nugget zone (NZ) and thermo-mechanically affected zone to heat-affected zone continuing to NZ.

Developments of microstructure and mechanical properties in friction stir welding of thick 5083 aluminium alloy

Developments of microstructure and mechanical properties in friction stir welding of thick 5083 aluminium alloy

Experimental investigation on material flow and mechanical properties in friction stir welding of copper sheets

This paper focuses on the mechanism of onion rings emergence by analyzing optical macrographs and micrographs of friction stir welds on the copper alloy produced by a non-threaded tool pin. Also tensile tests, hardness measurements, and microstructural evaluations were performed on the welded specimens. The microstructural study shows that the weld has lamellar structure and the bands are sections of weld layers, which are produced by forward and rotational movement of the tool. The weld layers with same form, similar to the pin form, reside into each other with tool rotation and form a quasi-spherical shape. On the transverse cross section of the weld, the boundary of the layers is emerged like concentric quasi-circles, which are called onion rings. Each layer is emerged with one tool rotation, and its distance with the next consecutive layer is equal to the weld pitch. The formation of onion ring structures is due to the cutting of the weld layers with the same recesses and dimples. Hardness measurements show that the core of onion-ring-shaped structure at two points near the weld surface and weld root possesses maximum hardness. The average hardness of weld decreases from upper surface toward bottom until mid-depth, where then increases. HAZ has lower hardness on RS compared to that of AS. The scanning microhardness evaluation technique can be used as a complement method to the conventional hardness measurement procedures.

Comparison of Microstructure and Mechanical Properties of friction Stir welding of Al 6082 aluminum alloy with different Tool Profiles

This study aimed at the analysis of the metallurgical and Mechanical properties FSW joints welded with different tool profiles. In this project, Experiments are performed for friction stir welding of Al 6082 aluminum alloy with different tool profiles. The welding was performed on a vertical milling machine. The welds are produced by varying the tool profiles; the rotational speed was maintained at 1400 rpm and the welding speed was kept constant 90 mm/ min. The Microstructure analysis resulted in distinct lamellar bands and various degrees of intermixing that were correlated with different tool profiles. Tensile tests were conducted as per ASTM standards and, an increase in the tensile strength is observed with the increase in the number of the edges of the tool. Scanning Electron Microscope is used to inspect the fracture surfaces which suggested low mechanical strength and failure through the stir zone is due to inadequate material intermixing

Modeling Mechanical Properties of FSW Thick Pure Copper Plates and Optimizing It Utilizing Artificial Intelligence Techniques

Friction stir welding (FSW) is an innovative solid state joining technique and has been employed in aerospace, rail, automotive and marine industries for joining aluminum, magnesium, zinc and copper alloys. In this process, parameters play a major role in deciding the weld quality these parameters. Using predictive modelling for mechanical properties of FSW not only reduce experiments but also is created standard model for predict outcomes. Therefore, this paper is undertaken to develop a model to predict the microstructure and mechanical properties of FSW. The proposed model is based on Ring Probabilistic logic Neural Network (RPLNN) and optimize it utilizing Genetic Algorithms (GA). The simulation results show that performance of the RPLNN algorithm with utilizing Genetic Algorithm optimizing technique compared to real data is reliable to deal with function approximation problems, and it is capable of achieving a solution in few convergence time steps with powerful and reliable results.

Effect of tool material on microstructure and mechanical properties in friction stir welding

Abstract Although the number of experimental studies investigating the effect of friction stir welding (FSW) parameters on joining properties have increased recently, there are not sufficient numbers of studies on the effect of the stirring tool material in friction stir welding. This study investigated the effect of stirring tool materials on microstructure, mechanical properties and residual stress of joints. Samples of 7075-T651 Al alloys were joined by FSW using uncoated and TiN-coated X210Cr12 alloy steel stirring tools. The welding processes were performed at rotational speeds of 900, 1250 and 1600 rpm and at a welding speed of 60 mm × min−1. Mechanical and metallographic tests were applied to the welded joints and residual stress analysis was performed using the hole drilling method. The best mechanical properties were determined in the welded samples joined by the uncoated tool at a rotational speed of 900 rpm. It was also determined that the TiN-coated tool negatively affected the mechanical and metallurgical properties of the weldements. Moreover, the highest longitudinal residual stresses were specified in the joining performed by the uncoated tool.

Studies on Microstructure and Mechanical Properties of GTAW, Laser and Friction Stir Welded ZM21 Magnesium Alloy

Present work pertains to welding of ZM21 magnesium alloy using three different welding techniques namely Gas Tungsten Arc Welding, Laser Beam Welding and Friction Stir Welding. After careful trial and error method, the process parameters were identified to produce defect free, full penetration welds successfully. The microstructure and mechanical properties of ZM21 magnesium alloy using GTAW, LBW and FSW processes were analyzed by optical microscopy, tensile testing and Vickers micro hardness measurements. The results show that the tensile properties of Friction stir welds and Laser beam welds are much better than those of gas tungsten arc welds. The formation of very fine grains in the friction stir welded region and absence of HAZ in LBW are found to be main reasons for better tensile properties. It has been concluded that the ZM21 magnesium alloy exhibits good weldability in all the three welding processes and laser beam welding process offers higher joint efficiency when compared with GTAW and FSW.

Neural Network and Genetic Algorithm Based Modeling and Optimization of Tensile Properties in FSW of AA 5052 to AISI 304 Dissimilar Joints

A prominent benefit of friction stir welding (FSW) process is to join sheets with dissimilar material. In such condition, the mechanical properties of dissimilar joints are highly affected by FSW parameters. In the present work, an attempt is made to find optimal parameter setting of tool rotary speed, welding speed and tool offset regarding maximum tensile strength and elongation for AA 5052 and AISI 304 dissimilar joints. For this purpose, firstly an intelligent correlation between mentioned factors and tensile properties was developed by using neural network. Then, the developed network was integrated with genetic algorithm to find optimal solutions to achieve desirable mechanical properties. Furthermore, the obtained result is verified by conducting confirmatory experiment. Results indicated that settings of 500 RPM tool rotational speed, 80 mm/min traverse speed and 2 mm tool offset causes maximization of both tensile strength and elongation. Also, this result was then discussed based on FSW process mechanism.