What is aluminium?
Aluminium is a silvery-white, light metal. It is the third most common element in the earth's crust after oxygen and silicon, with a share of 7.57%. However, due to its base metal properties, it occurs almost exclusively in bound form. In materials technology, the term 'aluminium' refers to all materials based on the element aluminium. This includes pure aluminium (containing at least 99.0% aluminium), ultra-pure aluminium (containing at least 99.7% aluminium), and aluminium alloys in particular, which are as strong as steel but only one third as dense.
Global bauxite production was expected to increase by 1.8% to 421.5 million metric tons (mt) in 2024. The top five bauxite-producing countries were:
Other significant producers included Guyana, which produces 1.7 million tons in 2024, and Rio Tinto's bauxite operations produced 58.7 million tonnes in 2024.
Aluminium is one of the light metals. These are used in many areas of technology due to their properties. Aluminium alloys are alloys that consist mainly of aluminium. Use the interactive explorer below to find the perfect alloy for your project. Click the filter buttons based on the properties you need to instantly narrow down your options and discover the right material for your application.
This is an overview of the designation system of wrought aluminium alloys EN 573-3/4 and EN 1706
AL AW alloy = Aluminium of Wrought Aluminium (AW Wrought Aluminium alloys)
AI AC alloys = Aluminium group of casting alloys AC (engl. aluminium cast)
In addition, there are also M (master alloy) and B (block metal).
AA stands for Aluminium Association and exists specifically for aluminium. It is used worldwide as the basis for aluminium standards and aluminium designations. It is identified by the prefix AA, followed by four digits. The digits are broken down as follows:
First digit: Main alloy component(s)
Second and third digits: Specific alloy designation (number has no meaning, but is unique)
Fourth digit: Ingots (0) or castings (1, 2).
The most common welding processes are TIG and MIG welding. Here, the oxide skin is removed by the cleaning effect in the arc. TIG welding is usually carried out under alternating current, MIG welding under direct current with positive polarity. Argon or argon-helium mixtures are used as shielding gases in these weld formation, higher performance and lower pore sensitivity: the disadvantages are the higher gas price and higher consumption during welding. Gas welding, which was common in the past, has lost importance because special, aggressive fluxes must be used here to remove the oxide skin, the effectiveness of which decreases with increasing Mg content and the residues of which can cause corrosion. The removal of flux residues is also time-consuming and requires special measures for occupational safety and environmental protection. This also applies to manual arc welding with coated stick electrodes, as their coating contains aggressive salts as fluxes.
Shielding Gas Functions
- Provides a plasma for commutation of current
- Protects the weld pool from reaction with air environment
- Provides cleaning action, which partially removes the aluminium oxide from the base material (DCEP)
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Argon |
Helium |
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Advantages |
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Good arc initiation and stability |
Higher arc voltage |
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More effective shielding |
Broad weld root width |
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Lower cost |
Reduced porosity |
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Good cleaning |
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Disadvantages |
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Narrow weld root width |
Poor cleaning |
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Poor arc initiation and stability |
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Higher cost |
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Higher flow rates required |
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Aluminium weld Argon
Aluminium weld Helium
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- Composition of the base material
- Heat input
- Sheet thickness
- Position of the weld
- Welding quality (appearance)
- Effort of welding work (productivity)
- Skill of the welder
This is carried out by grinding, milling or plasma cutting. Abrasives must not be plastic-bonded. Mechanical preparation usually dry finish. As a general rule, care must be taken that Opening angle for Y- seams is 70° and that the longitudinal face edges are broken on the root side (opposite side chamfered with 0.5 mm x 45°).
Butt welds without bar spacing on stainless CrNi steel pad fuses.
- Copper bath fuse
- Stainless steel bath fuse
- Bath fuse made of ceramic
- Bath fuse made of aluminium (remains in a part of the seam)
- Aluminium profile, which is built in the workpiece
- Melting point 2052°CWeather and corrosion resistance under oxidative conditions
- Good wear resistance (hardest material after diamonds)
- Transparent material
- Thickness of oxide grows quickly up to 10 nm (0,000010 mm)
- It can grow electrolytically and chemically up to 0,05 - 0,1 mm
- anodic oxidation
- Discoloration
- When oxidation becomes stronger, porosity increases
- Aluminium base material produces an oxide layer when it comes in contact with oxygen
- It has a high regeneration
- when the oxide layer is damaged, it regenerates by itself
- DC TIG welding of aluminium with (-) polarity and with argon shielding gas is impossible because the melting point of the oxide layer to the polarity is high, so the energy of the arc is not enough to break the oxide layer.
- DC TIG arc can melt the base material, but can not melt both sides because of the oxide layer in the root.
- Aluminium base material produces an oxide layer when it comes in contact with oxygen
- Oxide regenerates on its own when damaged.
- AC TIG arc efficiently breaks the oxide layer.
- Strongest oxide has AWS 5356 (seawater resistant).
- In cases when aluminium is oxidized, this layer must be removed before welding (5 mm in the area of the weld).
- Depth of the joint in the weld pool fuse depends on the sheet thickness
- If the depth is too shallow, the weld pool cools down too quickly, and defects may
- defects may occur in the weld
- Too deep a joint causes too large a root and too large a weld pool
- high heat input
- low welding speed
- wrong shape of the weld
| Material thickness (mm) |
A | B |
| ≤ 1,5 | 10 | 0,2 – 0,5 |
| ≤ 6,0 | 10 - 15 | 1,0 – 2,5 |
| ≥ 6,0 | 10 - 15 | 2,5 – 3,5 |
- When welding I-joints ( I, U and V-seam ) sharp edges should be removed mechanically (grinding etc).
- By removing the corners you get a defect-free root
Sharp root edges cause:
- Wrong seam profile
- Pores
- Oxide inclusions
- Risk of cracks
| Material Thickness | Seam preperation | Note |
| 0,9 - 1,6 mm | Square butt joint, Flare V-groove weld | |
| ≤ 3,8 mm | Square butt joint | If no backing plate possible to weld from both sides |
| ≤ 4,8 mm | Square butt joint, V groove weld | 1 or 2 layers, If no backing plate possible to weld from both sides |
| ≤ 6,4 mm | V groove weld | 1 or 2 layers, If no backing plate possible to weld from both sides |
| ≤ 9,5 mm | V groove weld | 1 or 2 layers, If no backing plate possible to weld from both sides |
- Gas flow must be higher than for steel welding
- Stick-out length should be 10 - 15 mm (The correct length for the protruding wire tip is 15 x wire diameter (mm) for high parameters and 10 to 12 x wire diameter (mm) for low parameters)
- Torch angle must be 60-80° piercing
- Welding by step technique i.e. welding step by step
- Do not use old filler metals (older than 1/2 year)
- Choose the right seam shape
- Best way to prepare the weld is for the welder to use a pool fuse to secure the weld
- Preheating is recommended for material thicknesses greater than 8.0 mm
When welding aluminium the torch always lead straight or slightly piercing 60-80° angle.
- Clean weld, no smoke on the surface
- Good gas shielding
- Better weld shape
In ''step'' welding, the weld is melted twice and gases have more time to escape from the weld pool.
- Lower porosity
- Better gas shielding and less surface oxidation
- Visually better weld
The primary cause of pore formation in the weld metal is the sudden decrease in gas solubility during solidification. Hydrogen is particularly prominent here, as any oxygen present is bound to AI2O3 and nitrogen forms aluminium nitride. The decreasing gas solubility leads to precipitation of submicroscopic gas bubble nuclei, which grow by further gas absorption and move upwards in the melt. The degassing is more difficult at high welding speeds and rapid molten pool stiffening, and thus pores are formed in the weld metal. The sources of hydrogen are manifold by the shielding gas hose material. Since the difference in water vapor partial pressure between the ambient air and the shielding gas stream is considerable, moisture can enter the shielding gas and the arc relatively easily by diffusion.
In general, the pore problem is greater in MIG welding than in TIG welding because less moist ambient air enters the shielding gas atmosphere in the relatively quiet TIG process.
- Clean and dry surfaces of base material and additional material
- Pretreatment by grinding, brushing, pickling, degreasing
- Quiet arc and torch guidance
- Turbulence-free shielding gas flow with correct dosage and purity
- Largely dimensioned and clean shielding gas nozzle
- Keep hose assembly short
- Use torch with closed cooling system
- Flush for a sufficiently long time before welding
- Provide root protection
- If possible, weld in position PA or PF. Avoid welding positions PC and PE
There is a risk of increased during solidification and shrinkage. This is particularly the case if the alloy has a large solidification interval and low-melting grain boundaries from eutectics. The tendency to crack depends strongly on the alloy type and must therefore always be taken into account when selecting te filler material. Table shows the hot cracking ranges and recommended minimum contents of silicon, copper and magnesium in the filler metal for some alloy types. The lead content in aluminium should always be as low as possible. End crater cracks can be avoided by an end crater filling program integrated in modern welding equipment or by welding on an additional run-out plate. Cracks in the seam root are often due to aluminium oxides and are preventer by lower plate chamfering.
Alloys of this composition can be age-hardened to high strength and are considered to be very sensitive to cracking: Fusion welding is therefore not possible or only possible to a very limited extent, depending on the level of copper content.
Depending on its composition, this alloy is generally susceptible to cracking and therefore a filler metal of the same type is not used, but welding is carried oud with CEWELD AISi5 according to EN ISO 18273. If the workpiece is to be anodized after welding, however, CEWELD AIMg3 is used as the filler metal. If high demands are made on the mechanical properties, the filler metal CEWELD AIMg4.5Mn should be selected.
AIZnMg alloys are age-hardenable and tend to crack during welding due to the amount of alloying constituents, they tend to crack during welding: welding of the same type is therefore not possible. The alloy AIZn4.5Mg1 is considered to have good weldability. Non-age-hardening CEWELD AIMg5 or CEWELD AIMg4.5Mn are used as standard.
The respective composition of these alloys is decisive for their susceptibility to cracking. AIMg alloys show maximum hot cracking susceptibility at 1.2% magnesium, while AISi alloys show maximum hot cracking sensitivity at around 0.75% silicon. As a rule of thumb, higher alloy filler metal is usually more resistant to cracking during welding.The filler metal is therefore clearly over-alloyed with 2% silicon or 3.5% magnesium in any case. Further improvements in welding safety can be achieved through the addition of mangenese or chromium, making AIMg4.5Mn more favourable in terms of weldability than the AIMg grades. If one of the materials is a magnesium alloy, the filler metal is based on this.
A direct joint between these materials with electric arc welding cannot be achieved with acceptable result. The main reasons for this are:
- The differences in melting points are too great (> 800°C). The consequence of this is aggravated by the differences in specific heat, heat of fusion, thermal conductivity, etc.
- The wettability of aluminium on iron is poor.
- Dissolved iron in aluminium may cause embrittlement by the formation of a brittle FeAI3-phase.AlsoAINi-alloysshows some intermetallic phases with less suitable properties.
Dissimilar joints between these alloys are therefore usually welded with an intermediate piece of bimetal or trimetal, so called ''inserts'', placed between the aluminium and the Ni- or Fe-based alloy. These inserts are generally produced by explosion welding. To avoid melting through the insert when welding on the Fe/Ni side, the insert must be thick enough. The greater the differences in melting points, the thicker the insert.
The welding is then performed with consumables suited for the chosen material combination. The mechanical properties of the joint will be comparable to those for the aluminium side.
Good results have been reported using the GTAW process to butter the steel side with AI-bronze and then weid it to the aluminium side using the MMA method. Electro plating can also be used to give a coating of Ni, Zn or Cu on the steel side (about 50 microns), but this is less safe due to the vulnerability of the coating.
Alloys between copper and aluminium show some very brittle intermetallic phases (CuAI2, CuAI, Cu3AI2), which makes welds between these alloy very difficult to produce. However, both the SAW and GTAW processes have been used to produce large electrical contact pieces.
The SAW process has been used for thicknesses between 12 and 20 mm. A cryolite rich flux was used together with AI-wire. The löngitudinal axis of the wire was displaced towards the copper side by about 0.5 times the thickness of the copper plate. The GTAW process was used for thinner workpieces in a tulip formed joint, using aluminium rods. The rods were fed so that a minimum of dilution from the copper side was achieved. Electroplating of the copper side (about 50 microns) with Ag, Sn, Zn and especially Ni provides improved wettability on this side and will therefore improve the total result of the welding operation.
