Weldability Of Aluminum Alloys Research Articles

Joining of Dissimilar alloy Sheets (Al 6063&AISI 304) during Resistance Spot Welding Process: A Feasibility Study for Automotive industry

Present design trends in automotive manufacture have shifted emphasis to alternative lightweight materials in order to achieve higher fuel efficiency and to bring down vehicle emission. Although some other joining techniques are more and more being used, spot welding still remains the primary joining method in automobile manufacturing so far. Spot welds for automotive applications should have a sufficiently large diameter, so that nugget pullout mode is the dominant failure mode. Interfacial mode is unacceptable due to its low load carrying and energy absorption capability. Strength tests with different static loading were performed in, to reveal the failure mechanisms for the lap-shear geometry and the cross-tension geometry. Based on the literature survey performed, venture into this work was amply motivated by the fact that a little research work has been conducted to joining of dissimilar materials like non ferrous to ferrous. Most of the research works concentrated on joining of different materials like steel to steel or aluminium alloy to aluminium alloy by resistance spot welding. In this work, an experimental study on the resistance spot weldability of aluminium alloy (Al 6063) and austenitic stainless steel (AISI304) sheets, which are lap joined by using a pedestal type resistance spot welding machine. Welding was conducted using a 45-deg truncated cone copper electrode with 10-mm face diameter. The weld nugget diameter, force estimation under lap shear test and T – peel test were investigated using digital type tensometer attached with capacitive displacement transducer (Mikrotech, Bangalore, Model: METM2000ER1). The results shows that joining of Al 6063 and AISI 304 thin sheets by RSW method are feasible for automotive structural joints where the loads are below 1000N act on them, it is observed that by increasing the spots per unit length, then the joint with standing strength to oppose failure is also increased linearly incase of interfacial failure mode and non linear for pullout failure mode.

Process Window for Friction Stir Lap Welding of Aluminum Alloy 6061

Precipitation-hardenable 6xxx series aluminum alloys are incorporated in many structural components with due consideration of their good combination of properties including a relatively high strength, outstanding extrudability and excellent corrosion resistance. Accordingly, AA6061 has been identified as a very good candidate material for structural lightweighting of transportation vehicles. However, the weldability of aluminum alloy (AA) 6061 by means of conventional technologies such as GMAW and GTAW methods is limited by sensitivity to solidification cracking. In this respect, friction stir welding (FSW) presents a tremendous potential for assembly of aluminum structures for the transportation industry due to the low heat involved that can mitigate crack formation and, thus, translate into improved mechanical performance of the assembly. In this work, FSW of 3.18 mm thick AA6061-T6 sheets in the lap joint configuration was investigated. This configuration is considered to be more challenging for assembly by FSW than the butt joint type due to the orientation of the interface with respect to the welding tools and the necessity to break the oxide layer on two aluminium alloy planar surfaces. Weld trials were performed to examine the influence of the FSW tool geometry and process parameters on the welding defects, microstructure, hardness and bend performance. Unacceptable material expulsion and/or significant thinning in one of the two overlapped sheets were produced under most conditions. A set of FSW tool geometries leading to a viable process operational window under which the risk of defects could be mitigated and/or eliminated was identified in this study.

가변 극성 아크의 알루미늄 용접성 향상에 관한 연구

Abstract Low arc weldability of aluminum alloy is enhanced by applying variable polarity TIG and the result is theoretically investigated to figure out the mechanism. Conventionally, it is well known fact that DCEP (reverse polarity) arc is effective on aluminum welding. The reason is due to oxide layer removal by plasmaion bombardment and therefore it is named as cleaning effect. Another fact of polarity characteristic is that DCEN shows higher heat input efficiency therefore conventional variable polarity arc used to apply DCEP portion as small as possible. However, higher DCEP portion shows bigger weldment in this research and it is explained by adopting a theory of arc concentration on oxide layer with tunneling effect which was not clearly mentioned before in several variable polarity TIG welding research. Disagreement between variable polarity TIG welding result and conventional arc polarity theory is rationally explained for the first time with help of electron emission theory. Key Words : Variable polarity, Arc, Aluminum, Weldability, Cleaning effect, GTA, TIG, DCEP

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

Measuring laser weldability of aluminium alloys using controlled restraint weldability test

Al–Mg–Si alloys are known to be highly susceptible to solidification cracking. Weldability results of laminated AA6061-T6 plates are presented in this paper when welded in full penetration keyhole mode using a 1030 nm, 10 kW Yb:YAG disk laser welding source with different welding conditions. Making use of the controlled restraint weldability (CRW) cracking test, a boundary has been established between crack and no crack conditions for different preloads. The originality of the CRW test is the cross-shaped test coupon that partitions the pre-stress unequally along the welding path. The CRW is proven capable of ranking the solidification cracking behaviour of weld metals deposited under different welding conditions.

Study of the weld ability of aluminum alloy 5083 H116 with pulsed arc GMAW (GMAW-P)

This research was based on the analysis of the weldability of aluminum joints, Alloy GL AW 5083 H116, with filler AWS 5.10 ER 5183 by GMAW-P process to determine the conditions of the heat-affected zone in the base material, depending on the heat input for the GMAW-P process with different pulsed technologies available in Colombia. The variables considered within this study were: welding positions (horizontal, vertical up, and overhead), type of welded joints (butt and fillet), and parameters for welding equipment (voltage, current, speed, power supply, speed development), and protective gas used (Argon, 100%). Non-destructive and destructive testing techniques were used to characterize the discontinuities found and the criteria to accept or reject the AWS D1.2 code (STRUCTURAL WELDING CODE - ALUMINUM by the AMERICAN WELDING SOCIETY). As a result, the investigation yielded the conditions for the application of filler material (ER 5183) on base material (alloy AW5083 GL H116), supported by Welding Procedure Specifications Documents (WPS) and Procedure Qualification Record (PQR) to implement in aluminum welding at the COTECMAR shipyard.

System analysis of the weldability of aluminium alloys

System analysis of the weldability of aluminium alloys

Aluminum alloy welding by using a high power direct diode laser

Aluminum alloys are the focus of increasing attention from the automobile industry because of their light weight, high formability, and easy recyclability. In this report, a 4 kW high power direct diode laser was used to examine the weldability of aluminum alloys of AA5022 and AA6016. A heat conduction welding type bead shape was produced with a very smooth bead surface. Full penetration butt welding was possible up to a welding speed of 12 m/min for 1 mm thick AA5022 and 6 m/min for 1 mm thick AA6016. Welding phenomena were observed with a high speed video camera. Very quiet welding phenomena were observed, with no spattering or laser plasma formation.

Laser Weldability of Aluminum Alloy and Steel

With the intention of improving butt or lap joint of dissimilar materials, specially devised weld beads together with lap and butt-joints were produced between A5052 and SPCC, where A5052 butt-joint was melted by heat-conduction of SPCC weld bead in addition to the formation of a limited weld fusion zone at the lap part in A5052 alloy. The thickness of intermetallic compounds at the butt-joint interface was approximately 2 μm and free of cracks. It was also revealed that crack-free lap weld metals were formed between aluminum alloy and steel when the penetration was controlled to be of less than 0.3 mm in depth at small heat input. It was moreover found that the majority of a laser weld fusion zone solidified as alpha(bcc)-iron phase containing small amount of aluminum, and cracks were absent in the case of hard intermetallic (AlxFey type) layer of less than 10μm zone. It was confirmed that a weld with lap and butt joints possessed high strength (leading to the load 3500 N to 4,380 N for 40 mm width specimen). In addition, SPCC and A1100 or A5052 were subjected to lap welding with a cw YAG laser, where one to three passes were performed to produce wider bonded areas. Dissimilar steel and aluminum joints with good mechanical properties were obtained, since the fracture occurred in the aluminum alloy base metal in the tensile test. It is concluded that welded joints of high strength can be produced between aluminum alloy and steel with proper devices.

Effects of high-intensity ultrasonic-wave emission on the weldability of aluminum alloy 7075-T6

In this work, high-intensity ultrasonic wave is conducted into aluminum alloy 7075-T6 to observe the effect of emission waves on the weldability during inert gas tungsten arc (GTA) welding. Through the heat-affected zone (HAZ) and the weld, the ultrasonic-wave emissions with different paths are examined and directly correlated to the heating time, dwell time, cooling rate, as well as peak temperature of the thermal cycle, and to the grain growth, weld penetration, and hardness of the weldment. In addition, a methodology based on the characteristic curves of the relative amplitude ratios of the reflected longitudinal wave and vertical shear wave for improving the weldability of aluminum alloy 7075-T6 is presented.

Surface and microstructural characterization of laser beam welds in an aluminum alloy

The weldability of aluminum alloys is one of the main requirements to be considered for their application in the automotive and aerospace industry. In this work, the weld joints of an AA7020 alloy obtained by laser process were characterized by scanning electron microscopy, energy-dispersive x-ray spectrometry, wavelength-dispersive x-ray spectrometry, and x-ray photoelectron spectroscopy. The laser process can be described as a high-speed solidification process. The solidification rate can be estimated from the correlation among several solidification rates and the corresponding dendritic/cellular spacings, and the value calculated for this rate was 3.0×103 K/s. The inclusions present in the base metal were identified as (Cr,Fe)4Si4Al13, which were not observed in the fused zone. The fused zone microstructure showed two distinct phases: an aluminum solid solution and fine precipitates of MgZn2. The transition from the base metal to the fused zone presented a narrow heat-affected zone. A strong depletion of Zn was observed, and this does not influence the hot tearing susceptibility since hot cracks were not observed in the weld zone.

CO2 laser weldability of aluminium alloys (Report 4). Effect of welding defects on mechanical properties, deformation and fracture of laser welds

(2000). CO2 laser weldability of aluminium alloys (Report 4). Effect of welding defects on mechanical properties, deformation and fracture of laser welds. Welding International: Vol. 14, No. 1, pp. 12-18.

Friction weldability of aluminium alloys to carbon steel

Friction weldability of aluminium alloys to carbon steel

CO2 laser weldability of aluminium alloys (Report 3). Metallurgical characteristics of laser welds

(1999). CO2 laser weldability of aluminium alloys (Report 3). Metallurgical characteristics of laser welds. Welding International: Vol. 13, No. 9, pp. 683-692.

CO2 laser weldability of aluminium alloys (Report 1): Effect of welding conditions on melting characteristics

Summary A series of systematic studies was undertaken to clarify the effect of CO2 laser welding conditions on melting characteristics, porosity formation, cracking susceptibility, hardness profiles, macro- and micro-distribution of Mg, and tensile properties of aluminium alloys. Bead-on-plate welding was performed on different commercially available alloys such as A5052, 5083, 5182, 6061 and 7N01 with a CO2 laser under various conditions of laser power, welding speed and defocused distance. In this paper, the influence of various welding conditions on melting characteristics was investigated from a fundamental viewpoint. In particular, laser beam modes and pressure distribution under various gas flow rates were measured, and it was consequently demonstrated that melting behaviour was greatly affected by the laser mode in the welding direction and the gas flow rate or pressure. Also the effect of Ar/He gas ratio on melting was investigated, and it was revealed that the use of Ar was beneficial to weld more highly-conductive and reflective alloys at lower power and higher welding speed, while a higher content of He was good for higher power and lower welding speed. Furthermore, it was confirmed that a larger amount of Mg was evaporated even under conditions producing a shallow weld molten pool leading to more deeply penetrated welds.

CO2 laser weldability of aluminium alloys (2nd Report): Defect formation conditions and causes

Summary This paper describes the results of a systematic study to clarify the effects of CO2 laser welding conditions on porosity formation in commercial A5052, A5083, A5182, A6061, and A7N01 aluminium alloys. The causes and mechanism of porosity are examined through observations and evaluations of weld beads based on radiographic inspection and analysis of the gas content in pores by Q-mass spectroscopy in a vacuum, and on the amount of hydrogen in base and weld metals. The effects of the welding conditions on the high-temperature (solidification) cracking susceptibility of aluminium alloys are also investigated. The results show that porosity is reduced under the following conditions: 1. a fairly long preflow time of argon shielding gas; 2. polishing of the plate surface to decrease or remove sources of hydrogen and oxygen; 3. a lower welding speed to help gas bubbles float to the surface or a higher welding speed to produce smaller pores; 4. defocusing conditions of moderate power densities; 5. use of nitrogen or helium instead of argon. Solidification cracks are present in laser-welded fusion zones of A6061 and A7N01 alloys produced at higher welding speeds. The solidification cracking susceptibility of the alloys is evaluated to be higher in the following sequence: A5182, A5083 A5052 A7N01 A6061. The high sensitivity of the latter to cracking is attributable to a wide brittle temperature range (BTR) and low ductility.

A rapid method of evaluating the weldability of aluminium alloys

A rapid method of evaluating the weldability of aluminium alloys

Evaluating the weldability of aluminium alloys using the ‘thermal’ testpiece

Evaluating the weldability of aluminium alloys using the ‘thermal’ testpiece

The surface state and weldability of aluminium alloys

Resistance spot welding can be carried out satisfactorily on aluminium alloys if a suitable surface state can be obtained and preserved during storage. The surface oxide at two different stages of the rolling process and after different final heat treatments of commercial Al-2.5%Mg sheet was investigated by electron spectroscopy for chemical analysis. The kinetics of oxidation were studied on polished specimens oxidized in air at 300, 400 and 500 °C for times between 2 min and 96 h. After the initial formation of a thin film of amorphous Al 2O 3, magnesium diffuses through the film and forms islands of MgO. After prolonged oxidation these islands grow to a considerable thickness and eventually the surface is completely covered by crystalline MgO. Pickling agents and mechanical abrasion were used to remove the oxide and the surface state was then analysed after storage in dry air, in an outdoor atmosphere and in water. Resistance spot welding was performed on sheets in the as-received state and after preparation by pickling in NaOH and oxalic acid. The quality of the welds was markedly improved after oxide removal. However, the very thin film left by pickling is not stable during storage. Controlled oxidation will be necessary to produce a storage-resistant film ensuring good weldability.

アルミニウムおよびその合金のMIG溶接における被包ガスへの窒素および酸素の添加について

In this study, the effects of nitrogen an/or oxygen added to shielding gas on the weldability of aluminum alloys were investigated.Test materials were welded by manual and machine MIG welding equipments under various welding conditions.Weldability was evaluated by various properties of welds, such as appearance, shape and depth of penetration, porosities, structures, mechanical properties and others.The results were as follows:(1) Addition of nitrogen to argon gas was apt to form brown scales on bead surface of aluminum and its alloys, particularly of Al-Mg alloys, but the bead shape was scarcely disturbed by the addition of up to 10% nitrogen.It increased the depth of penetration and improved the tensile strength with refined structures of weld metal. Furthermore, it reduced the porosities in commercially pure aluminum welds, though it was not always effective for reducing them in aluminum alloys, particularly in alloys containing magnesium considerably.(2) Addition of oxygen to argon gas was apt to cause the puckering phenomenon, but that of up to 5% oxygen gave a comparatively excellent bead shape with no puckering.It increased the depth of penetration and produced the welds with few porosities in both aluminum and its alloys.(3) Simultaneous addition of nitrogen and oxygen to argon gas disturbed the bead shape with remarkable scales.It tended to form inclusions in welds, while it increased considerably the depth of penetration and occasionally decreased the porosities.(4) Consequently, it was considered that addition of nitrogen gas up to 10% or that of oxygen gas up to 5% was effective in practical applications, but simultaneous addition of them was not desirable.