Varying Tool Rotational Speed Research Articles

Microstructure, mechanical, and force-torque generation properties of friction stir welded third generation Al/Li alloy at higher traverse speed

The third generation of aluminium lithium alloys has been used primarily in aircraft and spacecraft structures for customized facilities to reduce weight and improve performance. Therefore, the present study has investigated the implication of varying tool rotation speed (TRS) from 700 rpm to 1600 rpm on the force, torque, heat generation, microstructure, and mechanical strength of friction stir welded 2050-T34 Al-Cu-Li alloy plates at a constant higher traverse speed (10 mms−1) and tool tilt angles of 2°. The experimental results reveal that increasing TRS decreases the weldment surface's force, torque, ripple space, and grain size. However, the heat input increases during friction stir welding with increasing TRS. The joint efficiency (87.9 %) and tensile strength (343.5 MPa) are obtained maximum at higher TRS(1600 rpm). Further, mixed and ductile failure modes are observed at the lower and higher TRS, respectively.

Prediction of heat generation effect on force torque and mechanical properties at varying tool rotational speed in friction stir welding using Artificial Neural Network

Friction stir welding (FSW) has played a significant role in joining aerospace alloys. During this process, the tool rotational (TRS) speed has been found to significantly affect heat generation compared to other parameters. Therefore, the study has investigated the effect of heat generation on force-torque and mechanical properties at different tool rotational speeds (TRS) in the FSW process through experimentation followed by Artificial Neural Network (ANN) technique. Further, the influence of different TRS ranging between 600 and 1800 rpm with an increment of 400 rpm on considered responses; namely thermal weld cycle, microstructure, and grain distribution in nugget zone (NZ) for 2050-T84 Al-Cu-Li alloy plates, welded using FSW were also investigated. It is observed that the vertically downward force (Z-force), longitudinal force (X-force), and spindle torque (Sp. T) decrease with increasing TRS. It is also observed an increasing (up to 1400 rpm) and then decreasing trend for tensile strength and hardness of welded samples. Moreover, the generation of frictional heat and grain size in NZ is increased with increasing TRS from 600 to 1800 rpm. However, the scanning electron microscope (SEM) micrographs of all-welded samples revealed a ductile mode of tensile fracture. Furthermore, the obtained experimental results were validated using the ANN technique. A quite better agreement has been established among the predicted outcomes from ANN with experimental results.

A fuzzy model to predict the mechanical characteristics of friction stir welded joints of aluminum alloy AA2014-T6

AbstractFriction stir welding is a prominent technique for making defect-free joints of aluminum alloys. The aluminum alloy AA2014-T6 finds wide applications in aerospace, naval and automotive applications. This paper attempts to predict the tensile strength and hardness characteristics of friction stir welded aluminum alloy AA2014-T6 by a fuzzy logic model. Friction stir welding was carried out by varying tool rotational speed (700, 1,000 and 1,400rpm), welding speed (20, 35, 50mm/min) and axial force (10, 12, 14kN) at three levels. The tensile strength and hardness characteristics of the welded specimens were obtained from the experiments conducted as per Taguchi’s L27 orthogonal array. A Mamdani-type fuzzy logic model was developed to predict the tensile strength and nugget hardness characteristics of the FSW joints. The fuzzy model was evaluated by comparing the results of confirmation experiments with that of the results predicted by the model. The confirmation experiments were conducted with a new set of parameters other than the ones used for building the model. The fuzzy model exhibits marginal variations of 2.53% for tensile strength and 2.42% for weld nugget hardness compared to the results of the conformation experiments.

Numerical prediction of various defects and their formation mechanism during friction stir welding using coupled Eulerian-Lagrangian technique

Defective weld significantly hampers the quality of the weld and selection of optimum process parameter which produces defect-free weld is an experimental tedious task. A robust numerical model capable of predicting various types of defects is required to save cost and time. In the current work, a numerical model is developed based on coupled Eulerian-Lagrangian method and the concept of Volume of Fluid is incorporated to predict defects. It is the first attempt to numerically predict and analyze various types of defects such as tunnel, void, cavity, and root defects associated with friction stir welding. Defect formation is studied by varying tool rotation speed from 600 to 1500 rpm, welding speed from 30 to 180 mm/min, and tilt angle from 0 to 3°. The tilt angle of zero degree resulted in tunnel defect and one degree resulted in void and cavity. Tilt angle of two degree produced a defect-free weld. Also, parameters with a three-degree tilt angle yielded defective welds. The defect formation mechanism is correlated with temperature history, material flow, and axial force. A process parameter window is developed indicating the defective and non-defective weld conditions.

Effect of Rotation Speed and Steel Microstructure on Joint Formation in Friction Stir Spot Welding of Al Alloy to DP Steel

In this work, friction stir spot welding of 5754 aluminum alloy to dual phase steel was investigated using two different ratios of martensite and ferrite (0.38 and 0.61) for steel sheet initial microstructure and varying tool rotation speed (800, 1200 and 2000 rpm). The effect of these parameters on the joint formation was evaluated by studying the plunging force response during the process and the main characteristics of the joint at (i) macrolevel, i.e., hook morphology and bond width, and (ii) microlevel, i.e., steel hook and sheet microstructure and intermetallic compounds. The plunging force was reduced by increased tool rotation speed while there was no significant effect from the initial steel microstructure ratio of martensite and ferrite on the plunging force. The macrostructural characterization of the joints showed that the hook morphology and bond width were affected by the steel sheet initial microstructures as well as by the tool rotation speed and by the material flow driver; tool pin or shoulder. At microstructural level, a progressive variation in the ratio of martensite and ferrite was observed for the steel hook and sheet microstructure. The zones closer to the tool presented a fully martensitic microstructure while the zones away from the tool showed a gradual increase in the ferrite amount until reaching the ratio of ferrite and martensite of the steel sheet initial microstructure. Different types of FexAly intermetallic compounds were found in three zones of the joint; the hook tips, in the hooks close to the exit hole and in the corner of the exit hole. These compounds were characterized by a brittle behavior with hardness values varying from 456 to 937 HV01.

Influence of tool rotational speed on the evolution of microstructure and mechanical properties of precipitation-hardened Aluminium 6061 butt joint during friction stir welding

The present investigation aims to evaluate the influence of varying tool rotational speed (rotation per minute, rpm) on the mechanical properties and microstructural evolution within friction stir welded aluminium alloyAA6061-T6 joints. The effects of rpm underthe constant tool travel speedwere investigated by optical microscopy, field emission scanning electron microscopy (FESEM)and transmission electron microscopy (TEM)observation, tensile, fracture and micro-hardness test. Special attention was paid to the formation and evolution ofprecipitates.Results revealed that the tool rotational speedof 1300 rpmproduces highest hardness reaching to ∼69 HVN at the nugget zone (NZ), which could be attributed to the higher intensity of nano-sized re-precipitation. This specific tool rotational speed of 1300 rpm has been determined to be suitable to achieve the maximum joint efficiency of 70.6%. Significantly, the NZ is characterized with small equiaxed dynamically recrystallized grains. In a noteworthy findings, the NZ showed mostly either free from strengthening precipitate or trace of small tiny re-precipitates, while the thermo-mechanically affected zone (TMAZ) contains coarse precipitates with deformed and dynamically recovered grains. On the other hand, there was obvious grain growth with increasing rpm, substantiating more heat involvement with favourable thermal gradient. The experiment concludes thatthe rotational speed has an considerable effect on the precipitation characteristics, dislocation property and existence of finer second phase intermetallic compounds (IMC),which arethe predominant factors controlling the joint property.

Development of bobbin tool and influence of its design parameters on FSW joint

This work is focused on designing and developing a bobbin tool for Friction stir welding (FSW) of aluminium alloys. A 20 mm shoulder diameter was considered for the FSW tool on both sides of the tool probe, which has a cylindrical shape of 6 mm length and 6 mm diameter tooltip. The tool was made of high carbon high chromium steel. The tool probe was obtained by turning operation on the lathe machine. Supporting dies are made up of mild steel and are designed to hold the workpiece and provide enough clearance to travel the bobbin tool along with the welding. The fabricated bobbin tool was used to prepare weld joints of AA6063 through Bobbin tool FSW by varying tool rotational speed and feed rate as FSW parameters. The welded joints were subjected to find the Tensile strength and microhardness of the joints, and further investigation on material properties is done and observed for validation. The weld joints with bobbin tool friction stir welding (BTFSW) exhibiting better properties on the FSW joints.

Investigations of the effect of the tool rotational speed on friction stir welded joint on aluminium metal matrix hybrid composite

Aluminium alloy based hybrid composites with ceramic reinforcements has caught the interest of research nowadays. The addition of more than one reinforcement in aluminium alloy matrix leads to the fabrication of Aluminium Metal Matrix Hybrid Composite (AMMHC). The need for the present investigation arrives from the above considerations in exploring the potential of joining the newly developed AMMHC for automobile applications. The stir casted Al 6063 with reinforcement 5% wt. Silicon Carbide (SiC) and 5% wt. Boron Carbide (B4C) was prepared and joined by friction stir welding (FSW) route. The prime experimental work has been tried out in the FSW process by varying Tool Rotational Speed (TRS) from 800-1200 rpm. The effect of TRS on AMMHCs was studied by evaluating macro and microstructural parameters followed by microhardness and ultimate tensile strength. It was seen that the1000 rpm of TRS gives better properties than other processing conditions. This effect of TRS revealed that fine particle dispersion followed by higher join strength can be obtained for AMMHC. This fabrication of AMMHC and the FSW processing parameter was recommended for automobile component applications.

Use of Friction Extrusion to Fabricate Magnesium Alloy Wires with Rare Earths from Machined Chips

Magnesium alloy wires with rare earth elements were fabricated using friction extrusion by varying tool rotational speed in the range of 400 to 1200 rpm. Microstructure of wires fabricated usin 800 rpm consists finer equiaxed mg grains with finer precipitates homogeneously distributed along the grain boundaries. The strength of the wires fabricated under optimum parametes exhited a strength of 304 MPa which is 45 % higher than the tensile strength of as-cast material. Improper processing conditions results in undesirable microstrucutre and loss of strength values.-

Friction Stir Welding of Glass Filled Nylon 6 Composites

Nylons are high-performance, semi-crystalline thermoplastics with many attractive properties like chemical, physical, and mechanical properties. The aim of this research work is to investigate the feasibility of glass filled Nylon 6 composites by Friction stir welding (FSW). Glass filled Nylon 6 composites were fabricated by an injection molding process and joined by FSW technique with H13 tool steel having cylindrical pin profile. The effect of varying tool rotational speed (300, 600 and 900 rpm) and tool transverse speed (0.1, 0.2 and 0.3 mm/s) on the mechanical properties (ultimate tensile strength, percentile elongation, and Shore D hardness) and morphological properties of FSWed sections of glass filled Nylon 6 composites was investigated. The maximal tensile strength (40.32 MPa), which reached 51.32 % joint efficiency and percentage elongation (7.01%) was acquired at a tool rotational speed of 900 rpm and tool traverse speed of 0.1 mm/s with defect free welds. Tensile specimens of maximum weld tensile strength fractured occurred in TMAZ –HAZ at advancing side. There is a close relationship of tensile test results with fracture location and morphology

Microstructure, hardness and corrosion behaviour of friction-stir processed AA5083

PurposeThe purpose of this study is to refine the microstructure and improve the corrosion behaviour of aluminium alloy AA5083 by subjecting it to friction stir processing (FSP).Design/methodology/approachFSP trials are conducted as per central composite design, by varying tool rotation speed, tool traverse speed and shoulder diameter at three levels. The microstructure is examined and the hardness is measured for both the base material and the processed workpieces. The corrosion behaviour of the base material and processed workpieces is studied using potentiodynamic polarization technique for three different testing temperatures, and the corrosion current and corrosion rate are calculated.FindingsThe results reveal that FSP refined the grains, dispersed secondary phases, increased the hardness and improved the corrosion resistance of most of the friction stir processed specimens than the base material at all the three testing temperatures. Grain refinement and fine dispersion of ß phase improves the hardness and corrosion resistance of most of the FSPed specimens. However partial dissolution of ß phase decreases the hardness in some of the specimens. Most of the FSPed specimens displayed more positive potential than the base material at all the testing temperatures representing a higher nobility than the base material, as a result of fine dispersion of secondary phase particles in the matrix. Large pits formed on the surface of the base specimen indicating a higher corrosion rate at all three testing temperatures. The SEM image of FSPed specimens reveals the occurrence of very few pits and minimal corrosion products on the surface, which indicates lower corrosion rate.Originality/valueThe corrosion mechanism of the friction stir-processed AA5083 specimens is found to be a combination of activation and concentration polarization.

Evaluating weld properties of conventional and swept friction stir spot welded 6061-T6 aluminium alloy

6061-T6 aluminium alloy is a tempered grade aluminium material that is extensively used, particularly in space and automotive applications. The conventional and swept friction stir spot welding (FSSW) joints are prepared by varying tool rotational speed at four different levels. The mechanical properties, microstructure and mode of failure in both types of FSSW are evaluated and reported. The high plastic deformation and fine grains influenced the increase in hardness of the weld joints based on the Hall-Petch equation. The highest lap shear strength of 5.31 kN is observed in swept FSSW sample prepared at 1400 rpm. Interestingly, 1600 rpm decreased the lap shear strength due to insufficient friction between base metal and tool in the higher tool rotational speed. The minimum microhardness is noticed in heat-affected zone (HAZ) of both cases. Conventional FSSW samples showed shear fracture, nugget pullout fracture and circumferential fracture under lap shear loading, whereas swept FSSW showed only the circumferential fracture.

Modified friction stir clinching of dissimilar AA2024-T3 to AA7075-T6: Effect of tool rotational speed and penetration depth

There is a need to overcome the formation of stress-raisers such as geometric-differential flow-induced defects in modified friction stir clinched dissimilar aluminum alloys in order to improve joint performance. This paper thus examines the modified friction stir clinching of 2024-T3/7075-T6 aluminum alloys with the motive of inhibiting the flow-induced defect by varying tool rotational speed and penetration depth. The results depict that the combined increase in tool rotational speed and penetration depth cutback the severity of geometric-differential flow-induced defect at the weld nugget center due to better flowability and intermingling of materials. Low level of penetration depth induces the formation of repressed upward material flow and forms undesirable unfilled zone with an n-flow profile within the weld nugget owing to insufficient upward material flow and intermixing. Maximum failure stresses of 288.98 MPa (tensile) and 176.52 MPa (cross-tension) were obtained at 1400 rpm and 0.5 mm. Circumferential and defect-induced failure behaviors are the modes of failure in the joints produced at high and low penetration depth respectively.

Friction Stir Welding of AISI 316L Stainless Steel in a 3.5 NaCl Aqueous Solution: Metallurgical and Mechanical Characterization

Abstract Submerged friction stir welding (SFSW) was employed for joining AISI 316L stainless steel sheets. The effect of submerged friction stir welding on the metallurgical and mechanical properties of the weld joints was studied by varying tool rotational speed from 600 to 1,400 r/min, in steps of 400 r/min with other constant process parameters (welding speed of 55 mm/min, axial force of 12 kN, and tool tilt of 1.5°) in an artificially prepared 3.5 sodium chloride aqueous solution chamber. Characterization studies, such as scanning electron microscopy and electron backscattered diffraction, were used for studying the microstructural studies of the weld zone. The results of the experimental analysis reveal that the SFSW joints exhibited overall better joint strength, and the weld made at 1,000 r/min was superior in terms of strength and microstructural features to that of the base steel. The pitting corrosion behavior of the base steel and the weld joints depicts a stable pitting potential with no active passive behavior, in which the pitting corrosion resistance of all weld joints was marginally higher, especially the weld joint made at 1,000 r/min, which was superior to that of the base steel. The existence of the secondary precipitates was ruled out in all the cases, owing to lower peak temperatures and continuous (fast) cooling of the weld zone.

Monitoring of friction stir welding based on vision system coupled with Machine learning algorithm

The increase in utilization of FSW process demands online monitoring system for early detection and control of defects. This research attempts to develop a system for detection and classification of defective welds using weld surface image. Welding joints are produced at different welding condition by varying tool rotational speed, welding speed, tool shoulder diameter and pin diameter. The weld surfaces produced at different welding condition are captured using digital camera and processed to extract features. The features from weld surface image has been extracted using maximally stable extremal region algorithm and which is used as input for classification of weld joint. The Support Vector Machines is used for classification of weld using features from surface image. Support Vector Machines is trained with different kernel functions and found that linear and quadratic kernel function classify defect weld and good weld with accuracy of 95.8%.

Influence of tool rotation speed on microstructural characteristics and mechanical properties of friction stir welded AA2014-T6 aluminium alloy

Friction stir welding (FSW) is a promising solid-state welding process for precipitation hardening and high strength aluminium alloys. An experimental and theoretical investigation was carried out to check the significance of tool rotation speed on microstructural characteristics and tensile properties of high-strength alloy AA2014. FSW joints were made with varying tool rotation speed from 1,100 rpm to 1,900 rpm with an equal increment of 200 rpm, while the other parameters such as welding speed, shoulder diameter and tool tilt angle were kept constant. The strength of FSW joints was correlated with microhardness, microstructure and fractographs. The joint fabricated with the tool rotation speed of 1,500 rpm, welding speed of 50 mm/min, shoulder diameter of 6 mm and tool tilt angle of 1.5° exhibited superior strength (376 MPa) than the other joints. It could be achieved by the balanced flow of material and defect-free in the stir zone.

Influence of tool rotation speed on microstructural characteristics and mechanical properties of friction stir welded AA2014-T6 aluminium alloy

Friction stir welding (FSW) is a promising solid-state welding process for precipitation hardening and high strength aluminium alloys. An experimental and theoretical investigation was carried out to check the significance of tool rotation speed on microstructural characteristics and tensile properties of high-strength alloy AA2014. FSW joints were made with varying tool rotation speed from 1,100 rpm to 1,900 rpm with an equal increment of 200 rpm, while the other parameters such as welding speed, shoulder diameter and tool tilt angle were kept constant. The strength of FSW joints was correlated with microhardness, microstructure and fractographs. The joint fabricated with the tool rotation speed of 1,500 rpm, welding speed of 50 mm/min, shoulder diameter of 6 mm and tool tilt angle of 1.5° exhibited superior strength (376 MPa) than the other joints. It could be achieved by the balanced flow of material and defect-free in the stir zone.

Mechanical characterization of Al/Ti-6Al-4V surface composite fabricated via FSP: a comparison of tool geometry and number of passes

Aluminium alloys specifically the 1100 grade are used majorly in the manufacturing industries. However, the alloy experiences wear while being used which in turn causes reduction in the service life of this alloy. One of the most common causes of failure in aluminum alloy is wear and with the aim to improve the wear resistance of this aluminum alloy, friction stir processing (FSP) was used to fabricate the surface composite of the Al/Ti-6Al-4V system. The Ti-6Al-4V particles were mixed into the 1100 Al alloy by employing two (2) different tool geometries (i.e., square shape and threaded taper) with a varying number of passes from 1–3 passes and a varying tool rotational speed of 600 and 1200 rpm. The results of this study showed that the tool shape, tool speed and the number of passes play significant role in the distribution of the reinforcing particles, which consequently affect the hardness, microstructural modifications, tensile properties and wear performance of these composite samples. The highest wear resistant composite was attained with threaded taper tool with 3 passes at 1200 rpm. Furthermore, the composite realized a wear resistance of 50% increment and a 40% reduction in friction coefficient compared to the 1100 Al alloy, this composite consequently exhibits the highest hardness and strength.

Properties of lap welds in low carbon galvanized steel produced by tool assisted friction welding

Linear lap welds in very thin plates of galvanized steel were produced using tool assisted friction welding, a friction stir welding related technique. The morphological and microstructural analysis of the welds produced with varying tool rotational speed (up to 1400 rpm), tool traverse speed (up to 1200 mm/min) and tool diameter (10–16 mm) revealed the absence of stirred material or important welding defects in most of the joints. For the welds produced with the higher tool traverse and rotational speeds, a strong asymmetry in the weld morphology was also observed. A change in the contact conditions between the tool and the workpiece, from sticking to sliding, is appointed as the main factor responsible for the asymmetry in the weld morphology. The asymmetry in welds morphology has important influence in the failure mode of the welds in lap shear test but no influence on the joint strength. Lap shear strengths similar to base material ultimate tensile strength were measured for most of the welds.

Incorporating oxygen-free copper to improve the microstructure and mechanical properties of friction-stir-welded joints for aluminum alloys

Abstract The main objective of the present work was to establish a friction-stir-welding process to weld dissimilar metal joints on AA6082 and AA6066 aluminum alloy plates. Joints were made while varying tool rotation speed at a constant traveling speed and at the same time adding oxygen-free copper reinforcement inside the weld nugget for the purpose of analyzing the microstructural evolution and mechanical properties of the joint. Results showed that the morphology of the microstructure in the weld nugget changed significantly with rotation speed. Optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that oxygen-free copper particles could be uniformly dispersed into the weld nugget because of higher rotation speeds. Because of the presence of reinforcement particles homogenously distributed inside the nugget zone, the mechanical properties, such as ultimate tensile strength and hardness of weld joint, were greatly improved.