Friction stir welding (FSW) is an advanced welding process to join similar and dissimilar materials. The weld quality of FSW is mostly connected to input parameters and machine nature. In this ...research work, two dissimilar AA2014 and AA7075 aluminum alloys were welded in FSW using Taguchi design of experiments. The input parameters: tool rotation speed, welding speed, axial force, and tool tilt angle; Output parameters: Tensile Strength and Microhardness. The surface topography of tested specimens has been analyzed through Scanning Electron microscopic analysis (SEM). The analysis of variance (ANOVA) tests had been performed to find the significant factors to maximize the output responses. The maximum tensile 214 MPa was obtained from the best input parameters: 1000 rpm of rotating speed, 45 mm/min of weld speed, 6KN of axial force, and 2˚ of tool tilt angle. The optimum microhardness (132.5Hv) was predicted from 60 mm/min of weld speed.
•Band patterns from the advancing side to the stir nugget center are detected in the self-reacting friction stir welding.•Meta-stable precipitates are all diminished in the stir nugget zone and the ...thermal mechanically affected zone.•The grain size of the stir nugget zone increases with the increase of welding speed.•The tensile strength of defect-free joint increases with the increase of welding speed.•The tensile fracture of defect-free joint is located at the heat affected zone on the advancing side.
The 4mm thick 6061-T6 aluminum alloy was self-reacting friction stir welded at a constant tool rotation speed of 600r/min. The specially designed self-reacting tool was characterized by the two different shoulder diameters. The effect of welding speed on microstructure and mechanical properties of the joints was investigated. As the welding speed increased from 50 to 200mm/min, the grain size of the stir nugget zone increased, but the grain size of the heat affected zone was almost not changed. So-called band patterns from the advancing side to the weld center were detected in the stir nugget zone. The strengthening meta-stable precipitates were all diminished in the stir nugget zone and the thermal mechanically affected zone of the joints. However, considerable amount of β′ phases, tending to reduce with increasing welding speed, were retained in the heat affected zone. The results of transverse tensile test indicated that the elongation and tensile strength of joints increased with increasing welding speed. The defect-free joints were obtained at lower welding speeds and the tensile fracture was located at the heat affected zone adjacent to the thermal mechanically affected zone on the advancing side.
The microhardness curve trend and its relationships with microstructure and misorientation were analyzed to enhance the comprehension of the microstructure and mechanical property of micro-areas in ...Ti6Al4V laser-welded joints with different welding speeds. The microhardness measured on the fusion line (Hm) is the highest from the weld center to the base metal. Hm increases with increasing weld width in a welded joint and increasing degree of the non-uniformity in all studied welded joints. The microhardness decreases from the weld metal to the base metal with decreasing amount of martensite α’ and increasing amount of original α phase. When the microstructure is mainly composed of martensite α’, the microhardness changes with the cooling rate, grain size of the martensite, and peak values of the fraction of misorientation angle of the martensite in a wide weld metal zone or weld center at different welding speeds, whereas the difference is small in a narrow weld metal zone.
To reveal the effects of welding speed on welding process stability, microstructure, and mechanical performance of SUS304 weldments fabricated by local dry underwater pulsed metal inert-gas welding ...(LDU-PMIG), the electrical signals and droplet transfer behaviours of welding process, phase morphologies and distributions, grain sizes and grain boundary characteristics, microhardness, and tensile strength of these weldments were investigated in this work. The results indicated that with the increase of welding speed from 9.0 mm/s to 16.2 mm/s, the welding process stability first improved and then deteriorated. The more rapid water cooling rate caused by the increase of welding speed led to the δ-ferrite morphological evolution from skeletal to lath, which promoted the transformation from brittleness to ductility in the weld mechanical performance. Furthermore, the proportions of small-size grains (less than 10 μm) and low-angle grain boundaries (2–15°) first increased and then decreased, which determined the same variation trend in the comprehensive mechanical performance of weldments. The weldment obtained at 12.6 mm/s exhibited the highest microhardness, tensile strength and elongation, which achieved 70.0 %, 92.3 %, and 61.6 % of base metal. These results are conducive to enhance the SUS304 LDU-PMIG weldment quality and facilitate its application in marine equipment field.
•Elimination of hot cracking in the EBW of AA2024-T351 by controlling the welding speed and heat Input.•Reduction of hot cracking sensitivity by increasing the welding speed in EBW.•Reduction of hot ...cracking tendency by decreasing the heat input in EBW.
Hot cracking sensitivity of AA2024-T351 in the electron beam welding (EBW) was evaluated and the effects of welding speeds and heat input on the hot cracking were investigated. In this research, welding speed was set to 15–40 mm/s and microstructure of the welded zone was studied thoroughly by scanning electron microscopy (SEM). Appearance and geometry of weldments were also observed by stereo microscope. Microstructural observations showed that the hot crack length decreased with the increasing welding speed and decreasing the heat input and, as a result, in welding speed of 30 mm/s and heat input of 150 J/mm the crack-free weldment was achieved. The relationship between the welding speed and microstructure of the welded zone was also discussed. It could be concluded that decreasing the heat input alleviated thermal stresses and strains improved the grain structure, hence prevented nucleation and growth of hot cracks in the weld metal.
Friction stir welding process is a solid-state welding process, use non-consumable rotating tool to produce joints, it has been widely used for joining of similar and dissimilar materials in ...automobile, aerospace, railway and other industries. In the present work, Taguchi methodology based on L16 orthogonal array has been used to investigate the influence of rotational speed (rpm), welding speed (mm/min), axial force and water head (mm) on the UTS (Ultimate Tensile Strength) of the weld joints during the FSW (friction stir Welding) of AA 7039 alloy plates. The results shows that rotational speed is the most significant FSW condition that affect the UTS followed by welding speed, water head and axial load. Also, for the developed model, R2 value has been achieved as 0.999 and adjusted R2 value is equal to 0.997, which indicate excellent agreement between experimental and predicted values.
Annealed Ti–6Al–4V alloy sheets with 1 and 2
mm thickness are welded using a 4
kW Nd:YAG laser system. The effects of welding speed on surface morphology and shape, welding defects, microstructure, ...hardness and tensile properties are investigated. Weld joints without or with minor cracks, porosity and shape defects were obtained indicating that high-power Nd:YAG laser welding is a suitable method for Ti–6Al–4V alloy. The fusion zone consists mainly of acicular α′ martensite leading to an increase of approximately 20% in hardness compared with that in the base metal. The heat-affected zone consists of a mixture of α′ martensite and primary α phases. Significant gradients of microstructures and hardness are obtained over the narrow heat-affected zone. The laser welded joints have similar or slightly higher joint strength but there is a significant decrease in ductility. The loss of ductility is related to the presence of micropores and aluminum oxide inclusions.
•Critical restraint width could be employed to evaluate solidification cracking susceptibility during laser welding.•The wider the critical restraint width is, the higher the solidification cracking ...susceptibility is.•FA mode, fine grain and zigzag interface are conducive to reduce solidification cracking susceptibility.
A novel evaluation method was developed for evaluating solidification cracking susceptibility of austenitic stainless steel using trapezoidal hot cracking test laser welding. By changing different chemical compositions and welding speeds, the critical restraint width was named and regarded as a new index to evaluate cracking susceptibility. First of all, the average critical restraint width of SUS310S, 316 and 302 was measured as 22.97 mm, 18.17 mm and 17.38 mm during laser welding at a speed of 1.0 m/min, respectability. Single phase austenite under mode A appeared in 310S while the other could form austenite and a small amount of ferrite based on mode FA, therefore, the solidification cracking susceptibility was 310S > 316 > 302. Then, the critical restraint widths of SUS310S and 304 had a tendency of decrease with increasing welding speed from 0.5 m/min to 1.0 m/min during laser welding. The lower heat input could decrease primary and secondary dendrite arm spacings, causing a reduction in the segregation degree. In addition, the fine dendrite along grain boundary of weld center could contribute to form zigzag interface which would be beneficial to interrupt the continuous residual liquid film. Thus, the solidification cracking susceptibility tended to decrease with an increase in laser welding speed from 0.5 m/min to 1.0 m/min. Above all, the developed evaluation method could improve the applicability, feasibility and progressiveness of hot cracking test.
AA2219 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio. Compared to the fusion welding processes that are ...routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters and tool pin profile play major roles in deciding the weld quality. In this investigation, an attempt has been made to understand the effect of welding speed and tool pin profile on FSP zone formation in AA2219 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different welding speeds. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square pin profiled tool produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles.
•The magnesium alloy and 304 stainless steel were successfully joined via nanosecond pulsed laser welding.•Highest tensile shear force of 298.7 N was obtained at the speed of 30 mm/s.•Three fracture ...modes produced at various welding speeds were clarified.•The welding temperature field of magnesium/steel joint was simulated.
Nanosecond pulse laser welding was performed on AZ31B magnesium alloy and 304 stainless steel to investigate the impact of welding speed on the joining process. The temperature field of the magnesium/steel laser welding process was simulated using COMSOL software. The findings revealed that a welding speed of 10 mm/s resulted in significant spattering and larger porosity defects in the joint due to excessive heat input. However, when the welding speed was increased to 30 mm/s, these defects disappeared, and the porosity decreased to a minimum, leading to an increased bonding area at the interface. As the speed increased, the heat input decreased, making it more challenging for the porosity to escape from the molten pool and resulting in the formation of larger pores. The shear force test results indicated that the highest shear force was 298.7 N at a welding speed of 30 mm/s. The reduction in porosity and greater penetration depth of the magnesium alloy contributed to the desired mechanical performance. Additionally, the fracture modes were classified as button pullout failure (BPF), base material tearing failure (BTF), and interface failure (IF). The outermost weld seam served as the initial fracture path for both BPF and BTF modes, with BTF ultimately fracturing in the steel base material during tearing. Oxide inclusions, porosity, and the angle of distortion contributed to the fracture path of IF.
