Combined effect of inoculation and magnetic arc oscillation on microstructure and tensile behaviour of type 2090 Al–Li alloy weld fusion zones
01 Aug 2000-Science and Technology of Welding and Joining (Taylor & Francis)-Vol. 5, Iss: 4, pp 257-264
TL;DR: In this article, a type 2090 Al-Li alloy was gas tungsten arc welded with two different filler materials corresponding to types 2319 (Al 6.3Cu) and 4043 (Al 5.2Si).
Abstract: In the development of Al–Li alloys for aerospace structures, their behaviour during welding plays an important role. One way of improving weldability is to refine weld solidification structures, which can be achieved by a variety of means. In this work, a type 2090 Al–Li alloy was gas tungsten arc welded with two different filler materials corresponding to types 2319 (Al–6.3Cu) and 4043 (Al–5.2Si). Inoculation with titanium together with arc oscillation through an imposed alternating magnetic field was used to refine the weld fusion zone microstructures. Post-weld aging and tensile testing were employed to assess possible improvements in performance. It was found that the combined treatment of inoculation and magnetic oscillation resulted in fully equiaxed, fine grained structures and that this led to a noticeable increase in aging response and tensile properties, especially ductility.
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TL;DR: In this paper, a defect zone was defined in the welded specimens to investigate the effects of porosity on the joint tensile behaviour, and the porosity aggravated the inhomogeneous deformation in the welding zone, which accelerated the failure of the specimen and lowered the global ductility significantly.
Abstract: Aluminium–lithium (Al-Li) alloys are very attractive for aerospace applications due to their outstanding properties, such as high specific strength, high rigidity and good resistance to corrosion and fatigue, compared to conventional aluminium alloys. The butt joints of Al-Li 2A97-T3 alloy sheet produced by fibre laser welding with ER2319 filler wire were investigated in this paper. Uniaxial tensile tests have been performed to determine the nominal mechanical properties of the joints with and without porosities. In addition, a defect zone was defined in the welded specimens to investigate the effects of porosity on the joint tensile behaviour. The post-weld strength prediction (PWSP) model in a previous study has been extended by including the effects of the porosity in the welds to predict the overall response of the butt joints. The experimental and the modelling results show a good agreement, with the yield strength having a deviation lower than 5%. Both the yield strength and the ductility of the tensile specimens were observed to have decreased with the presence of porosities. The porosities aggravated the inhomogeneous deformation in the weld zone. Higher strain rate was found in the defect area than the remaining weld zone during plastic deformation, as the porosity in the specimen caused inhomogeneous deformation. It was found that this accelerated the failure of the specimen and lowered the global ductility significantly.
28 citations
Cites background from "Combined effect of inoculation and ..."
...The addition of lithium not only reduces the material density but also significantly increases the elastic modulus, thereby increasing the specific strength and stiffness of the alloys [1, 2]....
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TL;DR: In this article, an attempt was made experimentally to use different gas tungsten arc welding (GTAW) techniques and modify the filler chemistry with addition of scandium (Sc) and zirconium (Zr) in order to improve the mechanical properties of the AA2219 weld joints.
Abstract: Aluminium alloy AA2219 is a high strength alloy widely used for aerospace application. One of the drawbacks of most of the high strength aluminium alloys is that they suffer from poor weldability. However, AA2219 is an exception due to the presence of more copper that helps in healing cracks by providing extra eutectics. Although AA2219 has excellent weldability, the strength of a welded joint is only 35–45% of the base metal. The loss of strength is due to the dissolution of the strengthening precipitates during melting. Therefore, there is a need to improve the fusion zone strength of AA2219 welds. In this study, an attempt was made experimentally to use different gas tungsten arc welding (GTAW) techniques and modify the filler chemistry with addition of scandium (Sc) and zirconium (Zr) in order to improve the mechanical properties of the AA2219 weld joints. The application of the GTAW DCEN with Sc and Zr to the filler wire proved to be the most economical and perhaps the optimal choice for weld...
21 citations
TL;DR: The microtexture features of Nd:YAG laser welded joints in 5A90 aluminium-lithium (Al-Li) alloys were examined using electron back scattered diffraction (EBSD) as discussed by the authors.
Abstract: The microtexture features of Nd:YAG laser welded joints in 5A90 aluminium–lithium (Al–Li) alloys were examined using electron back scattered diffraction (EBSD). Microtexture was determined by means of the grain orientation image maps (OIM), pole figures (PF), misorientation angles and orientation distribution function (ODF) of the weld metal (WM), heat affected zone (HAZ) and unaffected base metal (BM) of the welded joint. The results show that there is a change of microtexture in the WM and HAZ of the welded joint in terms of the component and intensity of the texture. The HAZ of the welded joint inherits the texture characteristics of the BM, whereas the welding heat input has an important influence on the component C {112} . The WM of the welded joint is composed of predominantly equiaxed grains with a random microtexture.
13 citations
Cites background from "Combined effect of inoculation and ..."
...Aluminium–lithium (Al–Li) based alloys are desirable alternatives for aircraft and aerospace structural materials, due to lithium additions cause substantial reduction in density accompanied by large increase in elastic modulus, which results in appreciable improvement of specific strength and specific stiffness of the alloys.(1,2) However, some significant challenges remain in the large scale implementation of Al–Li alloys in the aerospace industry....
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TL;DR: In this paper, the effects of applying an electromagnetic interaction of low intensity (EMILI) on the microstructure and corrosion resistance of 7075-T651 Al alloy plates (13 mm in thickness) during modified indirect electric arc (MIEA) welding were investigated.
8 citations
TL;DR: In this paper, a new approach of integrating mechanistic model of electrode extension with the computational model of electromagnetic force is presented, wherein the apparent electrode extension is obtained by solving the electrode melting rate equation.
Abstract: Computation of the electromagnetic force over a wide range of consumable arc welding parameters is difficult with available models because of the need for experimentally evaluated electrode extension for every individual set of parameters. This becomes more complicated in case of submerged are welding, because the welding arc remains buried beneath flux. This study presents a new approach of integrating mechanistic model of electrode extension with the computational model of electromagnetic force, wherein the apparent electrode extension is obtained by solving the electrode melting rate equation. The proposed approach is demonstrated through a case on submerged arc welding. The effect of current, voltage, electrode diameter, contact tip to workpiece distance and polarity, on the electromagnetic force, is determined and analysed. This investigation shows that detrimental effects of welding electromagnetic force can be restricted without compromising productivity because after initial rapid increase...
7 citations
References
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01 Sep 1981-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: The mechanisms of grain refinement have been examined for magnetically stirred gas tungsten arc (GTA) welds completely penetrating thin sheets of several aluminum alloys in this article.
Abstract: The mechanisms of grain refinement have been examined for magnetically stirred gas tungsten arc (GTA) welds completely penetrating thin sheets of several aluminum alloys. Grain refinement in unstirred welds may be brought about by adding sufficient titanium to produce heterogeneous nucleation by Ti-rich particles. In some alloys magnetic stirring is shown to extend the range of welding conditions which produce a partially equiaxed structure, and to widen the equiaxed fraction of partially equiaxed welds. This is attributed to magnetic stirring lowering the temperature gradient, allowing nucleation and growth of Al-rich grains further ahead of the columnar interface growing in from the fusion boundaries. In alloys with low Ti levels, magnetic stirring may cause refinement by sweeping grains from the partially molten zone ahead of the advancing solidification interface. This mechanism requires that the partially molten zone be sufficiently wide, and that the grain size in this zone remain small.
106 citations
TL;DR: In this paper, the weld beads obtained under (i) continuous current (CC), (ii) pulsed current (PC), and (iii) arc oscillation (AO) conditions for their macro- and microstructural details were compared.
Abstract: Clad 2 mm thick sheets of Russian 1441 grade Al-Li alloys were welded using a gas tungsten arc welding process (GTAW). Comparisons were made between the weld beads obtained under (i) continuous current (CC), (ii) pulsed current (PC), and (iii) arc oscillation (AO) conditions for their macro- and microstructural details. In the case of CC GTAW, sound welds could be produced only under a narrow range of welding parameters. Centre line cracks, which occurred in CC GTAW welds under certain conditions, were halted by switching to PC or AO conditions while the welding was in progress. Microstructural refinement was significant in the case of PC and AO GTA welding.
105 citations
TL;DR: In this paper, the effect of arc oscillation on grain structure and solidification cracking in GTA welds of 5052 aluminum alloy was investigated using a four-pole magnetic arc oscillator and a modified fishbone crack test.
Abstract: The effect of arc oscillation on grain structure and solidification cracking in GTA welds of 5052 aluminum alloy was investigated using a four-pole magnetic arc oscillator and a modified fish-bone crack test. Two different mechanisms of crack reduction were identified: one in the low frequency range of arc oscillation and the other in the high frequency range. The former was the alteration of the orientation of columnar grains, while the latter was grain refining. Neither mechanism was operative in the intermediate frequency range and solidification cracking was severe, especially when the amplitude of arc oscillation was small. Alteration of grain orientation was obtained in welds made with transverse and circular arc oscillations, but not longitudinal arc oscillation. Grain refining, on the other hand, was achieved in welds made with all three types of arc oscillation patterns. The differences between the response of alloy 5052 to arc oscillation and that of alloy 2014 observed previously were discussed.
84 citations
Abstract: Lithium-containing aluminium alloys have reduced density and increased elastic modulus compared with conventional aluminium alloys. Many such alloys are currently under development for aircraft applications, which usually involve mechanical fastening. Consequently, the weldability of lithium-containing aluminium alloys is currently receiving relatively little attention. The weldability of lithium-containing aluminium alloys is reviewed. The vast majority of the welding studies performed have been on the Soviet Al-5 wt% Mg-2 wt% Li alloy, 01420. Alloy 01420 and other lithium-containing aluminium alloys are indeed fusion weldable, and weldments having high joint efficiencies have been made.
46 citations
TL;DR: The weldability of aluminium-lithium alloys is reviewed with emphasis on alloys that are being commercialized: 2090, 8090 and Weldalite™ 049 as mentioned in this paper.
Abstract: The weldability of aluminium-lithium alloys is reviewed with emphasis on alloys that are being commercialized: 2090, 8090 and Weldalite™ 049. These alloys are weldable, although hotcracking susceptibility has been reported for 2090 and 8090 when welded with certain conventional filler alloys. Mechanical property data from weldments made by several techniques are emphasized. Weld-zone porosity problems, discussed at length in a 1985 review in this journal, have largely been controlled by proper weld pretreatment and gas shielding. Interest in the weldability of aluminium-lithium alloys has taken on increased significance because of their potential to reduce the weight of space launch systems, whose fabrication most often involves welding.
42 citations