A5052-H112 합금의 겹치기 마찰교반접합 건전성

Stationary shoulder technology was used in friction stir lap welding (FSLW) in the present study. Joint formation, microstructure, and lap shear failure load (LSFL) of the traditional FSLW joints and FSLW joints assisted by external stationary shoulders were mainly investigated. To further prove its advantage, the external-assisted stationary shoulders with different diameters were also used. Results show that compared with the traditional FSLW joint, smooth surface with very small flash, without shoulder marks can be attained by the assisted external stationary shoulder. With decreasing the welding speed from 200 to 50 mm/min, effective lap width (ELW) gradually becomes bigger, effective sheet thickness (EST) gradually becomes smaller on the FSLW joint assisted by external stationary shoulders. FSLW joints by the assisted external stationary shoulder own bigger LSFL than the traditional FSLW joints. Using bigger shoulder diameter, bigger LSFL can be obtained. Shear fracture and tensile fracture modes can be observed during the lap shear test. LSFL is found to be connected with the fracture mode and the hook morphology.

In the present study, stationary shoulder technology was used to fabricate 6061-T6 friction stir lap welding (FSLW) joints. Effects of tool rotating speed on joint features and lap shear properties of the lap joints were mainly discussed. Similar to SSFSW, lap joint with smooth surface, without flash, shoulder marks and inner defects can be obtained using the stationary shoulder system. With increasing the rotating speed, effective sheet thickness (EST) firstly increases and then decreases. Effective lap width (ELW) gradually increases. The maximum EST and ELW are attained at 1200 and 1600 rpm, respectively. The maximum lap shear failure load of 17.01 kN is attained using rotating speed of 1400 rpm. The SSFSLW joints fracture in two modes: tensile fracture and shear fracture. All joints present ductile fracture mode.

Friction stir welding (FSW) is a solid state welding used for joining similar and dissimilar aluminum alloys which are hard to weld by conventional fusion welding processes. In this study friction stir lap welding (FSLW) Joints are made for similar aluminum alloys (AA1100 to AA1100) and(AA6061to AA6061) sheets of 3mm thickness and those alloys have low to medium strength and have difference in melting temperature and other physical properties.FSLW processes were carried out by conventional technique. The friction stir lap welding of similar aluminum alloys was carried out by varying the welding parameters, such as tool rotation speeds (1000, 1250 and 1600pm) and travel speeds (35, 75 and 100mm) and pin length of ( 5.4 mm) with using cylindrical threaded pin geometry or profile. Many tests and inspections were performed such as X-Ray radiographic and tensile shear test .Microhardness and microstructure observations by using optical and SEM were carried out at the best welding parameters. The above tests were used to evaluate the weld quality and joint efficiency under different welding parameters. The best welding parameters appeared in FSLW were 1250rpm and travel speed 100 mm/min. It was found that higher hardness value was (94.38HV) for 6061-T6 and 49HV for 1100-H112 in stir zone for both FSLW joints of AA6061-T6 and AA1100-H112 and that decrease toward the HAZ and base metals of AA1100 and AA6061.

Dual Phase (DP) steel, a type of Advanced High Strength Steel (AHSS) with a thickness of 1.7 mm, is used to fabricate single-hat components that are then joined to the base plate using two friction stir welding processes: friction stir lap welding (FSLW) and friction stir spot lap welding (FSSLW). It is difficult to join this assembly using fusion welding techniques. The welding variables for the FSLW process, tool rotation speed (TRS), tool traverse speed (TTS), and plunge depth (PD), were optimized using the design of an experiments-based response surface method by experimentally measured tensile shear failure load (TFL) of top hat assembly. For the FSSLW process, the welding variable TTS was replaced by dwell time (DT). Peak temperature, microstructure at different zones, microhardness mapping, and energy absorption capacity of both processes were evaluated under optimal welding conditions. For both processes, the stir zone and the heat-affected zone had the highest and lowest microhardness, which can be correlated with the level of martensite tempering, martensite lath spacing, polygonal ferrite volume, and precipitated carbides. Under optimum welding conditions, the TSL and energy absorption of FSLW joints were 14 kN and 170 J, respectively, which is 20% and 47 higher than the TSL and energy absorption of FSSLW joints.

Friction stir lap welding (FSLW) is expected to join the hybrid structure of aluminum alloy and steel. In this study, the Al-Mg-Si aluminum alloy and 301L stainless steel were diffusion bonded by FSLDW with the addition of 0.1 mm thick pure Zn interlayer, when the tool pin did not penetrate the upper aluminum sheet. The characteristics of lap interface and mechanical properties of the joint were analyzed. Under the addition of Zn interlayer, the diffusion layer structure at lap interface changed from continuous to uneven and segmented. The components of the diffusion layer were more complex, including Fe-Al intermetallic compounds (IMCs), Fe-Zn IMCs and Al-Zn eutectic. The largely changed composition and thickness of uneven and segmented diffusion layer at the lap interface played a significant role in the joint strength. The tensile shear load of Zn-added joint was 6.26 kN, increasing by 41.3% than that of Zn-not-added joint. These two joints exhibited interfacial shear fracture, while the Zn interlayer enhanced the strength of diffusion bonding by extending the propagation path of cracks.

Friction Stir Lap Welding (FSLW) is generally defined as a welding method, in which the heat is generated by friction and deformation. This study examines the effect of process parameters variation on the FSLW vertical force (Z- force). Additionally, this research is regarded as a research series of FSLW on aluminum sheets of A1100 and A1050. Previous research however, put more emphasis on joining aluminum sheets with Friction Stir Spot Welding (FSSW). Prior studies were intended to examine the resulting temperature, applying similar parameter variations. Relevant data are required to estimate the strength of jigs & fixtures when performing the connection process, which includes the Lap Joint type, with a constant tool rotation speed of 33000 rpm. The applied parameters include tool translation speed (feeding), tool tilt angles, and tool pin diameter. The machine employed in this process is a CNC machine type of EMCO TU CNC 3A. The test specimens include aluminum of A1100 and A1050. Data analysis is performed by Response Surface Methodology (RSM) to observe the parameter in the FSW process and to determine the vertical forces (Z-Force). The results of the Friction Stir Lap Welding (FSLW) processes produce the highest Z-force average, along with feed rate of 60 mm/minute, pin tool diameter of 2 mm, and a tilt angle of 4°. Meanwhile, the variation that produces maximum Z-force with the highest results utilizes feed rate of 80 mm/minute, pin diameter of 2 mm, and tilt angle of 3°.

Introduction. Aluminum alloys are in abundant demand of shipbuilding and aircraft industries. This study emphasizes on the effects of two different tool pin profiles on the tensile characteristics of welded joints made of AA8011 aluminum alloy welded joints. The joining technique used is friction stir welding (FSW) due to its unique characteristics such as very low heat affected zone when joining in a solid state. The microstructure and mechanical properties of the welded joint are influenced by the geometry of the tool and such parameters as rotational speed and traverse speed of the tool. The methods of investigation. The experiments on FSW were performed on universal milling machine with taper cylindrical and cylindrical threaded tool pin profiles using the three different combination of tool rotational and traverse speed (a) 320 rpm, 45 mm/min; b) 400 rpm, 50 mm/min; c) 575 rpm, 60 mm/min.). To analyze the joint characteristics, tensile tests were conducted and ultimate tensile strength as well as joint efficiency was calculated for individual joint. Results and Discussion. Based on the revised results, it is evident that higher RPM values have a positive impact on joint efficiency and tensile strength for both the taper cylindrical pin profile and the threaded cylindrical pin profile. The findings show that the joint efficiency and tensile strength are consistently higher for the threaded cylindrical pin profile compared to the taper cylindrical pin profile, regardless of the RPM and feed rate. From the results, it was found that joint efficiency and tensile strength is maximum at higher RPM irrespective of the tool pin profile i.e. 73.6 % and 123 MPa for taper cylindrical pin profile and 85 % and 142 MPa for threaded cylindrical pin profile at 575 rpm, 60 mm/min. These are the highest in comparison to 72.5 % and 119 MPa at 320 rpm, 45 mm/min and 70.1 % and 115 MPa at 400 rpm, 50 mm/min for taper pin profile tool and 82.6 % and 138 MPa at 320 rpm, 45 mm/min and 77.8 % and 130 MPa at 400 rpm, 50 mm/min for threaded cylindrical pin profile. Overall, the study demonstrates that joints obtained using the threaded cylindrical pin profile demonstrate higher joint efficiency and tensile strength than those prepared using the taper cylindrical pin profile. The highest joint efficiency and tensile strength of 84.5 % and 142 MPa, respectively, were achieved using the threaded cylindrical pin profile at 575 rpm and 60 mm/min.

The mechanism of joint efficiency for roller-compacted concrete (RCC) pavement joints and cracks is affected primarily by aggregate interlock or friction at the vertical interface of the joint. Current U.S. Army Corps of Engineers design procedures for RCC pavements make the conservative assumption that no joint efficiency is achieved at RCC pavement joints and cracks. The purpose of this study was to determine the degree of joint efficiency achieved at RCC pavement joints and cracks; to determine the factors that affect the joint efficiency, and to what degree; and to develop a regression model to predict the joint efficiency using those factors. The heavy weight deflectometer (HWD) and other devices were used to conduct nondestructive joint efficiency tests at 12 different RCC pavement sites around the United States. The joint efficiency results ranged from 22 percent to 89 percent, depending on the type of joint or crack tested. The joint efficiencies decreased significantly with increasing crack width...

Microstructure and mechanical properties of aluminum-steel dissimilar metal welded using arc and friction stir hybrid welding

With the rapid development of transportation and aerospace industries, the increasing emphasis on lightweighting has created a demand for advanced metal/polymer joining technologies. Underwater welding is an optimization way to reduce excessive heat effects of joints and improve welding efficiency. To mitigate the overflow of molten polymer matrix during the welding process of carbon fiber reinforced thermoplastic (CFRP) and aluminum alloy, process optimization experiments of water medium-assisted CFRP/aluminum alloy friction stir lap welding (FSLW) are carried out. For this purpose, a welding tool with water circulation function is designed and developed. The influences of water medium on material interface behavior, flow characteristics, and defect control are analyzed. By observing the joint boundary thickness and the interweaving combination of dissimilar materials under different water temperatures, the regulatory effects of water temperature on the microstructure and mechanical properties of the joint are studied. As the water temperature increases, the aluminum alloy is embedded into the CFRP in a plastically deformed state, and the thickness of the aluminum alloy at the joint bottom gradually increases, which enhances the load-bearing capacity of the dissimilar joint. The lap shear strength of the joint reaches 43.3 MPa at the 80°C water temperature.

Aluminum (1060Al) and stainless steel (SUS321, austenitic) were friction stir lap welded using a stir tool consisting of a cutting pin and a concave shoulder. Two welding processes characterized by plunge depth of the pin were designed. In process 1, the pin remains inside the Al metal and the pin tip approaches the stainless steel surface, while in process 2, the pin tip penetrates through the Al metal and was inserted into the stainless steel to generate a machining process. Morphological and compositional characterization of the joint revealed defect-free joining at the interface with a visible mixed layer corresponding to the possible phase FeAl3 and the solution of Fe in Al, resulting in high tensile strength of up to 89 MPa in process 2, while in process 1, the tensile strength was up to 71 MPa.

AA2014 aluminum alloy (Al-Cu alloy) has been widely utilized in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimize process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminum alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminum alloys. Hence, in this investigation, an attempt has been made to optimize friction stir lap welding (FSLW) parameters to attain maximum tensile strength using statistical tools such as design of experiment (DoE), analysis of variance (ANOVA), response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

Evolution of interfacial phases between Al alloy and high entropy alloy during annealing

In modern electronics solder joints are mostly composed of a lead-free solder alloy and interfaces of tin, nickel/gold or copper at the component and the circuit board side. Mostly SAC (SnAgCu) - alloys will be used in electronic products with high tin content. In the course of design and development the volume of these solder joints decreases rapidly. With this the solder joint exists only of some - one to four - single tin crystals with eutectic parts, and the percentage of the intermediate compounds that grow at the interface of the component/circuit board and solder increases rapidly. The orientation of the anisotropic tin crystal and the intermetallic phases plays an important role concerning the reliability of a solder joint. However, very few information about their physical and mechanical properties is known in literature depending on their orientation. The orientation of the tin crystals was determined by EBSD measurements in cross sections of solder joints and tensile specimens. Micro/Nano hardness measurements and tensile tests of differently oriented beta-tin crystals in solder joints and small tensile test specimens were made to get information whether the grain orientation influences the mechanical behaviour as hardness, Yield strength and tensile strength. The nano hardness was determined by Vickers indentation. For example, the Vickers hardness of different oriented tin crystals - between [320] and [001] orientation - ranges between 16 and 28 VHN (0.16-0.28 GPa). The [001] oriented crystals show the highest hardness. A correlation to the other material parameters as Yield strength and tensile strength will be discussed using stress-strain diagrams of different SAC alloys.

In this study, the performances of traditional rotating shoulder and stationary shoulder were compared during friction stir lap welding (FSLW) of 2024-T4 aluminum alloy. Formations, distortions, microstructure, and mechanical properties of the lap joints using different shoulders were mainly discussed. Results showed that smooth joint surface without shoulder marks and flash can be obtained due to the sealed barrier effect and scraping effect of the stationary shoulder. Joint with smaller distortion, which resulted from lower heat input, can be obtained using the stationary shoulder. Hook and cold lap can be largely depressed using the stationary shoulder, and therefore better lap shear properties can be obtained. When the retreating side of the upper sheet bore the main load during the lap shear test, joints using stationary shoulder owned about 50 % higher lap shear failure loads than the traditional joints. Moreover, although using different configurations, joints using the stationary shoulder owned rather uniform lap shear failure loads.