Aluminium–magnesium–silicon alloys (AlMgSi) are aluminium alloys—alloys that are mainly made of aluminium—that contain both magnesium and silicon as the most important alloying elements in terms of quantity. Both together account for less than 2 percent by mass. The content of magnesium is greater than that of silicon, otherwise they belong to the aluminum–silicon–magnesium alloys (AlSiMg).
AlMgSi is one of the hardenable aluminum alloys, i.e. those that can become firmer and harder through heat treatment. This curing is largely based on the excretion of magnesium silicide (Mg2Si). The AlMgSi alloys are therefore understood in the standards as a separate group (6000 series) and not as a subgroup of aluminum-magnesium alloys that cannot be hardenable.
AlMgSi is one of the aluminum alloys with medium to high strength, high fracture resistance, good welding suitability, corrosion resistance and formability. They can be processed excellently by extrusion and are therefore particularly often processed into construction profiles by this process. They are usually heated to facilitate processing; as a side effect, they can be quenched immediately afterwards, which eliminates a separate subsequent heat treatment.
The AlMg2Si system forms a Eutectic at 13.9% Mg2Si and 594 °C. The maximum solubility is 583.5 °C and 1.9% Mg2Si, which is why the sum of both elements in the common alloys is below this value. The stoichiometric composition of magnesium to silicon of 2:1 corresponds to a mass ratio of 1.73:1. The solubility decreases very quickly with falling temperature and is only 0.08 percent by mass at 200 °C. Alloys without further alloying elements or impurities are then present in two phases with the-mixed crystal and thephase (Mg2Si). The latter has a melting point of 1085 °C and is therefore thermally stable. Even clusters of magnesium and silicon atoms that are only metastable dissolve only slowly, due to the high binding energy of the two elements.
Many standardised alloys have a silicon surplus. It has little influence on the solubility of magnesium silicide, increases the strength of the material more than an Mg excess or an increase in the Mg2Si content, increases the volume and the number of excretions and accelerates excretion during cold and hot curing. It also binds unwanted impurities; especially iron. A magnesium surplus, on the other hand, reduces the solubility of magnesium silicide.[1]
In addition to magnesium and silicon, other elements are contained in the standardized varieties.
Dispersion particles have little influence on strength. If magnesium or silicon excrete on them during cooling after the solution annealing and, thus, do not form magnesium silicide as desired, they even lower the strength. They increase the sensitivity to deterrent. However, if the cooling speed is insufficient, they also bind excess silicon, which would otherwise form coarser excretions and thus reduce strength. The dispersion particles activate further even when cured. Sliding planes, so that theDuctility increases and, above all, intergranular fracture can be prevented. The alloys with higher strength therefore contain manganese and chromium and are more sensitive to deterrents.[2]
The following applies to the effect of the alloying elements with regard to dispersion formation:
6000 series are alloyed with magnesium and silicon. They are easy to machine, are weldable, and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach. 6061 alloy is one of the most commonly used general-purpose aluminium alloys.[4]
| 6005 | 98.7 | Si 0.8; Mg 0.5 | Extrusions, angles | |
| 6005A | 96.5 | Si 0.6; Mg 0.5; Cu 0.3; Cr 0.3; Fe 0.35 | ||
| 6009 | 97.7 | Si 0.8; Mg 0.6; Mn 0.5; Cu 0.35 | Sheet | |
| 6010 | 97.3 | Si 1.0; Mg 0.7; Mn 0.5; Cu 0.35 | Sheet | |
| 6013 | 97.05 | Si 0.8; Mg 1.0; Mn 0.35; Cu 0.8 | Plate, aerospace, smartphone cases[5] [6] | |
| 6022 | 97.9 | Si 1.1; Mg 0.6; Mn 0.05; Cu 0.05; Fe 0.3 | Sheet, automotive[7] | |
| 6060 | 98.9 | Si 0.4; Mg 0.5; Fe 0.2 | Heat-treatable | |
| 6061 | 97.9 | Si 0.6; Mg 1.0; Cu 0.25; Cr 0.2 | Universal, structural, aerospace | |
| 6063 & 646g | 98.9 | Si 0.4; Mg 0.7 | Universal, marine, decorative | |
| 6063A | 98.7 | Si 0.4; Mg 0.7; Fe 0.2 | Heat-treatable | |
| 6065 | 97.1 | Si 0.6; Mg 1.0; Cu 0.25; Bi 1.0 | Heat-treatable | |
| 6066 | 95.7 | Si 1.4; Mg 1.1; Mn 0.8; Cu 1.0 | Universal | |
| 6070 | 96.8 | Si 1.4; Mg 0.8; Mn 0.7; Cu 0.28 | Extrusions | |
| 6081 | 98.1 | Si 0.9; Mg 0.8; Mn 0.2 | Heat-treatable | |
| 6082 | 97.5 | Si 1.0; Mg 0.85; Mn 0.65 | Heat-treatable | |
| 6101 | 98.9 | Si 0.5; Mg 0.6 | Extrusions | |
| 6105 | 98.6 | Si 0.8; Mg 0.65 | Heat-treatable | |
| 6113 | 96.8 | Si 0.8; Mg 1.0; Mn 0.35; Cu 0.8; O 0.2 | Aerospace | |
| 6151 | 98.2 | Si 0.9; Mg 0.6; Cr 0.25 | Forgings | |
| 6162 | 98.6 | Si 0.55; Mg 0.9 | Heat-treatable | |
| 6201 | 98.5 | Si 0.7; Mg 0.8 | Rod[8] | |
| 6205 | 98.4 | Si 0.8; Mg 0.5;Mn 0.1; Cr 0.1; Zr 0.1 | Extrusions | |
| 6262 | 96.8 | Si 0.6; Mg 1.0; Cu 0.25; Cr 0.1; Bi 0.6; Pb 0.6 | Universal | |
| 6351 | 97.8 | Si 1.0; Mg 0.6;Mn 0.6 | Extrusions | |
| 6463 | 98.9 | Si 0.4; Mg 0.7 | Extrusions | |
| 6951 | 97.2 | Si 0.5; Fe 0.8; Cu 0.3; Mg 0.7; Mn 0.1; Zn 0.2 | Heat-treatable |
to the grain boundaries prefer silicon to be excreted, as it has germination problems. In addition, magnesium silicide is excreted there. The processes are probably similar to those of the AlMg alloys, but still relatively unexplored for AlMgSi until 2008. The phases excreted at the grain boundaries lead to the tendency of AlMgSi to brittle grain boundary breakage.
All information in mass percent. EN stands for European standard, AW for aluminium wrought alloy; the number has no other meaning.
| Numerically | Chemical | Silicon | Iron | Copper | Manganese | Magnesium | Chrome | Zinc | titanium | other | Other (individual) | Other (total) | Aluminum | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| EN AW-6005 | AlSiMg | 0.6–0.9 | 0.35 | 0.10 | 0.10 | 0.40–0.6 | 0.10 | - | - | - | 0.05 | 0.15 | Rest | |
| EN AW-6005A | AlSiMg(A) | 0.50–0.9 | 0.35 | 0.3 | 0.50 | 0.40–0.7 | 0.30 | 0.20 | 0.10 | 0.12–0.5 Mn+Cr | 0.05 | 0.15 | Rest | |
| EN AW-6008 | AlSiMgV | 0.50–0.9 | 0.35 | 0.30 | 0.30 | 0.40–0.7 | 0.30 | 0.20 | 0.10 | 0.05–0.20 V | 0.05 | 0.15 | Rest | |
| EN AW-6013 | AlMg1Si0.8CuMn | 0.6-1.0 | 0.5 | 0.6-1.1 | 0.20 - 0.8 | 0.8-1.2 | 0.10 | 0.25 | 0.10 | - | 0.05 | 0.15 | Rest | |
| EN AW-6056 | AlSi1MgCuMn | 0.7-1.3 | 0.50 | 0.50-1.1 | 0.40 - 1.0 | 0.6-1.2 | 0.25 | 0.10–0.7 | - | 0.20 Ti+Zr | 0.05 | 0.15 | Rest | |
| EN AW-6060 | AlMgSi | 0.30–0.6 | 0.10 - 0.30 | 0.10 | 0.10 | 0.35–0.6 | 0.05 | 0.15 | 0.10 | - | 0.05 | 0.15 | Rest | |
| EN AW-6061 | AlMg1SiCu | 0.40–0.8 | 0.7 | 0.15–0.40 | 0.15 | 0.8-1.2 | 0.04 - 0.35 | 0.25 | 0.15 | - | 0.05 | 0.15 | Rest | |
| EN AW-6106 | AlMgSiMn | 0.30–0.6 | 0.35 | 0.25 | 0.05–0.20 | 0.40 - 0.8 | 0.20 | 0.10 | - | - | 0.05 | 0.15 | Rest |
Conditions:
| Numerical[9] | Chemical (CEN) | Condition | E-module/MPa | G-module/MPa | Elongation limit/MPa | Tensile strength/MPa | Elongation at break/% | Brinell hardness | Bending change resistance/MPa |
|---|---|---|---|---|---|---|---|---|---|
| EN AW-6005 | AlSiMg | T5 | 69500 | 26500 | 255 | 280 | 11 | 85 | n.b. |
| EN AW-6005A | AlSiMg(A) | T1 | 69500 | 26200 | 100 | 200 | 25 | 52 | n.b. |
| T4 | 69500 | 26200 | 110 | 210 | 16 | 60 | n.b. | ||
| T5 | 69500 | 26200 | 240 | 270 | 13 | 80 | n.b. | ||
| T6 | 69500 | 26200 | 260 | 285 | 12 | 90 | n.b. | ||
| EN AW-6008 | AlSiMgV | T6 | 69500 | 26200 | 255 | 285 | 14 | 90 | n.b. |
| EN AW-6056 | AlSi1MgCuMn | T78 | 69000 | 25900 | 330 | 355 | n.b. | 105 | n.b. |
| EN AW-6060 | AlMgSi | 0 | 69000 | 25900 | 50 | 100 | 27 | 25 | n.b. |
| T1 | 69000 | 25900 | 90 | 150 | 25 | 45 | n.b. | ||
| T4 | 69000 | 25900 | 90 | 160 | 20 | 50 | 40 | ||
| T5 | 69000 | 25900 | 185 | 220 | 13 | 75 | n.b. | ||
| T6 | 69000 | 25900 | 215 | 245 | 13 | 85 | 65 | ||
| EN AW-6061 | AlMg1SiCu | T4 | 70000 | 26300 | 140 | 235 | 21 | 65 | 60 |
| EN AW-6106 | AlMgSiMn | T4 | 69500 | 26500 | 80 | 150 | 24 | 45 | n.b. |
| T6 | 69500 | 26200 | 240 | 275 | 14 | 75 | <75 |
AlMgSi can be used in two different ways through aHeat treatment can be hardened, whereby hardness and Strength rise, while ductility and Elongation at break. Both begin with the Solution annealing and can also be used with mechanical processes (Forging), with different effects:
If time passes after quenching and hot curing (so-called interim storage), then the achievable strength decreases during hot curing and only occurs later. The reasons are the change in the material cold curing during temporary storage. However, the effect only affects alloys with more than 0.8% Mg2Si (excluding Mg or Si surpluses) and alloys with more than 0.6% Mg2Si if Mg or Si surpluses are present.
To prevent these negative effects, AlMgSi can be annealed after quenching at 80 °C for 5–30 minutes, which stabilizes the material condition and temporarily does not change. The heat curing is then maintained. Alternatively, a step quenching is possible in which temperatures are initially quenched to be applied during hot curing. The temperatures are maintained for a few minutes to several hours (depending on temperature and alloy) and then completely cooled to room temperature. Both variants allow the workpieces to be processed in the deterred state for some time. Cold curing begins in the event of a longer waiting time. Longer treatment times increase the possible storage period, but reduce the formability. Some of these procedures are protected by patents.
Stabilization has other advantages: The material is then in a definable state, which allows repeatable results in the subsequent processing. Otherwise, for example, the time of interim outsourcing would have an impact on theRebound at theBending so that a constant bending angle would not be possible over several workpieces.
A transformation (forging, rolling, bending) leads to metals and alloys strain hardening, an important form of increasing strength. With AlMgSi, however, it also has an influence on the subsequent warming. Cold forming in the hot-cured state, on the other hand, is not possible due to the low ductility in this state.
Although cold forming directly after quenching increases the strength through strain hardening, it reduces the increase in strength through strain hardening and largely prevents it for from 10%.
On the other hand, cold forming in a partially or fully cold-hardened state also increases the strength, so that both effects add up.
If cold forming (in the quenched or cold-hardened state) is followed by hot forming, this takes place more quickly, but the strength that can be achieved is reduced. The higher the strain hardening, the higher the yield point, but the tensile strength does not increase. If, on the other hand, the cold forming takes place in the stabilized state, the achievable strength values improve.[10]
AlMgSi is one of the aluminum alloys with medium to high strength, high fracture resistance, good welding suitability, corrosion resistance and formability.[11]
They are used, among other things, for bumper, bodies and for large profiles in the Rail vehicle construction. In the latter case, they were largely responsible for the changed design of rail vehicles in the 1970s: previously, riveted pipe structures were used. Thanks to the good extrusion compatibility of AlMgSi, large profiles can now be produced, which then can be welded.[12] They are also used in aircraft construction, but there they are AlCu and AlZnMg preferred, but not or only difficult are weldable. The weldable higher-strong AlMgSiCu alloys (AA6013 and AA6056) are used in the Airbus models A318 and A380 for ribbed sheets in the aircraft hull used, where through the Laser welding, weight and cost savings are possible.[13] Swelding is cheaper than the usual in aircraft construction Rivets; The overlaps required during riveting can be eliminated during welding, which saves component mass.[14] [15] [16]