Papers by Keyword: AA 5052 Aluminium Alloy

Abstract: Conventional Friction Stir Welding (FSW) is that weld materials are joint at room temperature by stirring softened materials due to frictional heat of rotating tool. Therefore, high speed and high efficiency would be expected, as pre-heating make weld materials more softened, as well known that yield point goes lower due to heating. In this study, FSW was done to improve welding speed on FSW of aluminum alloy (A5052) for high vacuum vessel for processing of electronics devices. As the result, welding speed was 2.0 times to more than 3.0 at 300 oC comparing with conventional FSW at room temperature, using improved a milling machine with heater.

Abstract: The effects of strain path reversal on the microstructure in AA5052 have been studied using high resolution EBSD. Deformation was carried out using two equal steps of forward/forward (F/F) or forward/reverse (F/R) torsion at a temperature of 300°C and strain rate of 1s-1 to a total strain of 0.5. In both cases the deformation microstructure in the majority of grains analysed consisted of microband arrays clustering at specific angles to the macroscopic deformation axes. For the F/F condition microbands clustered around -20° and +45° to the maximum principle stress direction, whilst for the F/R condition significantly more spread in microband angle was observed. This suggests that the microbands formed in the forward deformation have or are dissolving and any new microbands formed are related to the deformation conditions of the final strain path. This leads to the conclusion that instantaneous deformation mode determines the orientation of new microbands formed whilst a non-linear strain path history influences the range of misorientation angle in the material through the dissociation of previously formed microbands and the formation of new microbands at the new straining condition, leading to a lower level of misorientation angle. Analysis of material subjected to static annealing at 400°C for 1 hour appears to correspond with these observations as the F/F material was completely recrystallised with a fine grain structure whilst the F/R material had no major signs of recrystallisation.

Abstract: The effects of strain path reversal on the macroscopic orientation of microbands in AA5052 have been studied using high resolution electron backscatter diffraction. Deformation was carried using two equal steps of forward/forward or forward/reverse torsion at a temperature of 300°C and strain rate of 1s-1 to a total equivalent tensile strain of 0.5. In both cases microbands were found in the majority of grains examined with many having more than one set. The microbands appear to cluster at specific angles to the macroscopic deformation. For the forward/forward condition microbands clustered around -20° and +45° to the maximum principle stress direction and at ± 30-35° to the principal strain direction. For the forward/reverse condition significantly more spread in microband angle was observed though peaks were visible at ±35° with respect to principal stress direction and at -40° and +30° with respect to the principal strain direction of the reverse torsion. This suggests the microbands formed in the forward deformation have or are dissolving and any new microbands formed are related to the deformation conditions of the final strain path.

Abstract: The effects of strain path reversal, using forward and reverse torsion, on the microstructure evolution in the aluminium alloy AA5052 have been studied using high resolution electron backscatter diffraction. Deformation was carried using two equal steps of forward/forward or forward/reverse torsion at a temperature of 300°C and strain rate of 1s-1 to a total equivalent tensile strain of 0.5. Sections of the as-deformed gauge lengths of both test specimens were then annealed at 400°C for 1 hour in a salt bath in order to investigate their subsequent recrystallisation response. In both strain path histories the deformation substructure in the grains analysed consisted of microband arrays within an equiaxed dislocation cell structure. The material subjected to forward/forward deformation did, however, have a slightly greater number of low angle boundaries, i.e. boundaries < 15° misorientation, whilst the forward/reverse material had some grains containing little evidence of substructure. On annealing both materials had significantly reduced levels of low angle boundaries but only the forward/forward material had an increased number of high angle boundaries and a reduced grain size, indicating recrystallisation had only occurred in this material. This would suggest that the deformation microstructure within the forward/forward condition was sufficient to initiate and maintain recrystallisation whilst the microstructure produced by the forward/reverse test contained insufficient nuclei or internal energy to produce a recrystallised material within 1 hour. Further work is now required at different annealing times in order to determine if the major effect of strain path is on retarding nucleation, growth or both.

Abstract: The microstructure of friction stir processed AA5052 sheets is investigated using Scanning Electron Microscopy (SEM) and Orientation Imaging Microscopy. The correlation between the generated forces during processing and the microstructure is evaluated. Observations indicate that the finest microstructure are achieved when the plunging forces are at minimum.

Abstract: Creep and creep rupture tests were carried out for friction-stir-welded (FSW) joints of 5052 aluminum alloy plates at temperatures between 573 and 723 K. The results were compared with those of the base metal. 5052-O plates of 20 mm in thickness were joined by FSW and round bar creep specimens were machined out of the welded plates. Tensile tests were also conducted at RT, 623 and 723K for both FSW joints and base metal. The tensile strength of the joints was almost the same as that of the base metal at room and elevated temperatures. However, the FSW joints showed appreciably higher minimum creep rate and shorter rupture time than the base metal at all the tested temperatures and initial creep stresses. Creep rupture of the joints always occurred within the plastically stirred zone with lower contraction of cross-sectional area. Thus, FSW joints of 5052 alloy plates showed lower creep strength than the base metal.

Abstract: Friction and wear behaviors have been studied between the untreated base material and the friction stir welds of 5052 aluminum alloy. To determine the wear mechanism surface microstructures of worn test samples were examined by scanning electron microscopy (SEM).Variation rule of wear-resistance property and coefficient of friction were investigated according to wear mass loss and moment of friction under different parameter condition. The results show that all of friction stir welds had lower coefficients of friction and higher wear resistance than base material. The abrasion loss of base material increased by six times when position pressure increased from 50N to 100N and the abrasion loss is as 10-20 times as that of friction stir welds. The value of friction-moment of friction stir welds is low and stable and abrasion principle had changed from grain abrasion to fatigue wear. Surface examination showed that adhesion and smearing was the main wear mechanism for friction stir welds.

Abstract: The microstructure and mechanical properties of spot friction stir welded A 5052 alloy were investigated with insertion depth of welding tool. As the insertion depth of welding tool increased, the size of stirring zone increased and the thickness of upper sheet decreased. The value of shear load was the lowest at the shallowest insertion depth and increased to the highest value of 3.35 kN at a 1.6mm of insertion depth. An increase in the pin insertion depth beyond 1.6mm did not result in further increase in the lap shear load. Spot friction stir welded joints showed shear fracture mode at shallower insertion depths and fracture mode changed to plug fracture mode as the insertion depth was deeper.