Aluminium–magnesium–silicon alloys
Aluminium–magnesium–silicon alloys(AlMgSi) arealuminium alloys—alloys that are mainly made ofaluminium—that contain bothmagnesiumandsiliconas 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 thealuminum–silicon–magnesium alloys(AlSiMg).
AlMgSi is one of thehardenablealuminum alloys, i.e. those that can become firmer and harder through heat treatment. This curing is largely based on the excretion ofmagnesium 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, highfracture resistance,good welding suitability,corrosionresistance andformability.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.
Alloy constitution[edit]
Phases and balances[edit]
The AlMg2Si system forms aEutecticat 13.9% Mg2Si and 594 °C. The maximumsolubilityis 583.5 °C and 1.9% Mg2Si, which is why the sum of both elements in the common alloys is below this value. Thestoichiometriccomposition 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 orimpuritiesare 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 onlymetastabledissolve 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 ofmagnesium silicide.[1]
Alloying elements[edit]
In addition to magnesium and silicon, other elements are contained in the standardized varieties.
- Copperis used to improve strength and hot curing in quantities of 0.2-1%. It forms the Q phase (Al4Mg8Si7Cu2). Copper leads to a denser dispersion of needle-shaped, semi-coherent excretion (cluster of magnesium and silicon). In addition, there is the phase before the for theAluminium-copper alloysare typical. Alloys with higher copper content (alloyings6061,6056,6013) are mainly used in aviation.
- Ironoccurs in all aluminium alloys as an impurity in quantities of 0.05-0.5%. It forms the phases Al8Fe2Si, Al5FeSi and Al8FeMg3Si6, which are all thermally stable, but undesirable because theybrittlethe material. Silicon surpluses are also used to bind iron.
- Manganese(0.2-1%) andChromium(0.05–0.35%) is deliberately added. If both are allocated at the same time, the sum of the two elements is less than 0.5%. Afterannealing,they form adispersionof excretions at at least 400 °C and thus improve strength. Chromium is mainly effective in combination with iron.
- As dispersion formers are comingzirconiumandvanadiumfor use.
Dispersions[edit]
Dispersion particleshave little influence on strength. If magnesium or siliconexcreteon them during cooling after the solution annealing and, thus, do not formmagnesium silicideas 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 fracturecan 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:
- The strength at room temperature hardly changes. However, the flow limit at higher temperatures rises sharply, which makes theReformability is limited and above all unfavourable in the extrusion is because it increases the minimum wall thickness.
- Therecrystallisationis made more difficult, which prevents coarse grain formation and has a positive effect onformability.
- Dislocationmovements are blocked at low temperatures, which improvedfracture toughness.
- Dispersions of AlMn bind oversaturated silicon during cooling after solution annealing. This improves crystallization and avoids excretion-free zones that otherwise arise at the grain boundaries. This improves the fracture behaviour from brittle toductileand intragranular.[3]
- The sensitivity to quenching increases because precipitated silicon is required for hardening. Alloys containing Mn or Cr must therefore be cooled faster than those without these elements.
6000 series[edit]
6000 series are alloyed with magnesium and silicon. They are easy to machine, areweldable,and can be precipitation hardened, but not to the high strengths that 2000 and 7000 can reach.6061 alloyis one of the most commonly used general-purpose aluminium alloys.[4]
| Alloy | Al contents | Alloying elements | Uses and refs |
|---|---|---|---|
| 6005 | 98.7 | Si0.8;Mg0.5 | Extrusions, angles |
| 6005A | 96.5 | Si0.6;Mg0.5;Cu0.3;Cr0.3;Fe0.35 | |
| 6009 | 97.7 | Si0.8;Mg0.6;Mn0.5;Cu0.35 | Sheet |
| 6010 | 97.3 | Si1.0;Mg0.7;Mn0.5;Cu0.35 | Sheet |
| 6013 | 97.05 | Si0.8;Mg1.0;Mn0.35;Cu0.8 | Plate, aerospace, smartphone cases[5][6] |
| 6022 | 97.9 | Si1.1;Mg0.6;Mn0.05;Cu0.05;Fe0.3 | Sheet, automotive[7] |
| 6060 | 98.9 | Si0.4;Mg0.5;Fe0.2 | Heat-treatable |
| 6061 | 97.9 | Si0.6;Mg1.0;Cu0.25;Cr0.2 | Universal, structural, aerospace |
| 6063& 646g | 98.9 | Si0.4;Mg0.7 | Universal, marine, decorative |
| 6063A | 98.7 | Si0.4;Mg0.7;Fe0.2 | Heat-treatable |
| 6065 | 97.1 | Si0.6;Mg1.0;Cu0.25;Bi1.0 | Heat-treatable |
| 6066 | 95.7 | Si1.4;Mg1.1;Mn0.8;Cu1.0 | Universal |
| 6070 | 96.8 | Si1.4;Mg0.8;Mn0.7;Cu0.28 | Extrusions |
| 6081 | 98.1 | Si0.9;Mg0.8;Mn0.2 | Heat-treatable |
| 6082 | 97.5 | Si1.0;Mg0.85;Mn0.65 | Heat-treatable |
| 6101 | 98.9 | Si0.5;Mg0.6 | Extrusions |
| 6105 | 98.6 | Si0.8;Mg0.65 | Heat-treatable |
| 6113 | 96.8 | Si0.8;Mg1.0;Mn0.35;Cu0.8;O0.2 | Aerospace |
| 6151 | 98.2 | Si0.9;Mg0.6;Cr0.25 | Forgings |
| 6162 | 98.6 | Si0.55;Mg0.9 | Heat-treatable |
| 6201 | 98.5 | Si0.7;Mg0.8 | Rod[8] |
| 6205 | 98.4 | Si0.8;Mg0.5;Mn0.1;Cr0.1;Zr0.1 | Extrusions |
| 6262 | 96.8 | Si0.6;Mg1.0;Cu0.25;Cr0.1;Bi0.6;Pb0.6 | Universal |
| 6351 | 97.8 | Si1.0;Mg0.6;Mn0.6 | Extrusions |
| 6463 | 98.9 | Si0.4;Mg0.7 | Extrusions |
| 6951 | 97.2 | Si0.5;Fe0.8;Cu0.3;Mg0.7;Mn0.1;Zn0.2 | Heat-treatable |
Grain boundaries[edit]
to thegrain boundariesprefer silicon to be excreted, as it hasgerminationproblems. 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.
Compositions of standardised varieties[edit]
All information in mass percent. EN stands for European standard, AW for aluminiumwroughtalloy; 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 |
Mechanical properties[edit]
Conditions:
- O soft (softannealed,whether or not warmly formed with the same strength limits).
- T1:quenchedby the hot forming temperature and cold outsourced
- T4:solution annealedand cold outsourced
- T5: quenched from the hot forming temperature and warm outsourced
- T6: solution annealed, quenched and warmly outsourced
- T7: solution annealed, quenched, hot outsourced and overhardened
- T8: solution annealed, cold solidified and hot outsourced
| 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 |
Heat treatment and curing[edit]
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:
- Solution annealing: At temperatures of about 510-540 °C, annealing is made, with the alloying elements in solution.
- Quenchingalmost always follows immediately. As a result, the alloying elements initially remain in solution even at room temperature, whereas they would form precipitates if they cooled down slowly.
- Cold curing: At room temperature, excretions gradually form that increase strength and hardness. In the first hours after quenching, the increase is very high, lower in the next few days, then only creeping, but not yet completed even after several years.
- Hot curing: At temperatures of 80-250 °C (usual are 160-150 °C), the materials are reheated in the oven. The hardening times are usually 5–8 hours. The alloying elements thus excrete faster and increase hardness and strength. The higher the temperature, the faster the maximum strength possible for this temperature is reached, but the lower the higher the temperature, the lower.
Interim storage and stabilisation[edit]
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 theformability.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.
Influence of cold forming[edit]
A transformation (forging,rolling,bending) leads to metals and alloysstrain 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 fordegrees of deformationfrom 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 theyield point,but thetensile strengthdoes not increase. If, on the other hand, the cold forming takes place in the stabilized state, the achievable strength values improve.[10]
Applications[edit]
AlMgSi is one of the aluminum alloys with medium to high strength, highfracture resistance,good welding suitability,corrosionresistance andformability.[11]
They are used, among other things, forbumper,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,rivetedpipe 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 areAlCuandAlZnMgpreferred, but not or only difficult are weldable. Theweldablehigher-strongAlMgSiCualloys (AA6013andAA6056) are used in the Airbus modelsA318andA380for 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]
References[edit]
- ^Smith, Andrew W. F. (2002).The Recrystallization and Texture of Aluminium-Magnesium-Silicon Alloys(Thesis).OCLC643209928.Archivedfrom the original on 11 March 2023.Retrieved10 March2023.
- ^Jacobs, M. H. (August 1969).The nucleation and growth of precipitates in aluminium alloys(Thesis).OCLC921020401.Archivedfrom the original on 9 December 2022.Retrieved11 March2023.
- ^Harris, I. R.; Varley, P. C. (April 1954). "Factors influencing brittleness in aluminium-magnesium-silicon alloys".Journal of the Institute of Metals.82:379–393.OCLC4434286733.OSTI4402272.
- ^"Aluminium in Marine Applications – Aluminium Alloys Used in Boat Building".AZoM.com.1 May 2008.Archivedfrom the original on 2 October 2022.Retrieved10 March2023.
- ^"Alloy 6013 Sheet Higher Strength With Improved Formability"(PDF).Archived fromthe original(PDF)on 22 December 2017.Retrieved8 March2023.
- ^"New, Sleeker Samsung Smartphone Built Stronger with Alcoa's Aerospace-Grade Aluminum".Business Wire(Press release). Alcoa. 4 June 2015.
- ^"Alloy 6022 Sheet Higher Strength with Improved Formability"(PDF).Archived fromthe original(PDF)on 27 August 2017.Retrieved8 March2023.
- ^Davies, G. (November 1988).Aluminium alloy (6201, 6101A) conductors.1989 International Conference on Overhead Line Design and Construction: Theory and Practice. London. pp. 93–98.ISBN978-0-85296-371-5.Archivedfrom the original on 11 March 2023.Retrieved11 March2023.
- ^Ostermann, Friedrich (2014).Anwendungstechnologie Aluminium[Application technology aluminum] (in German).doi:10.1007/978-3-662-43807-7.ISBN978-3-662-43806-0.[page needed]
- ^Swindells, N.; Sykes, C. (1938). "Specific Heat-Temperature Curves of Some Age-Hardening Alloys".Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences.168(933): 237–264.Bibcode:1938RSPSA.168..237S.doi:10.1098/rspa.1938.0172.JSTOR97238.S2CID94528199.
- ^Weser, A (2010)."Alkaline Earth Hydroxides".In Schütze, Michael; Wieser, Dietrich; Bender, Roman (eds.).Corrosion Resistance of Aluminium and Aluminium Alloys.John Wiley & Sons. pp. 37–45 [39].ISBN978-3-527-33001-0.Archivedfrom the original on 11 March 2023.Retrieved11 March2023.
- ^Ekşi, Murat (2012).Optimization of mechanical and microstructural properties of weld joints between aluminium - magnesium and aluminium - magnesium - silicon alloys with different thicknesses(Thesis).hdl:11511/22296.
- ^Mathers, Gene (2002)."Material standards, designations and alloys".The Welding of Aluminium and its Alloys.pp. 35–50 [44].doi:10.1533/9781855737631.35.ISBN978-1-85573-567-5.Archivedfrom the original on 11 March 2023.Retrieved11 March2023.
- ^Ostermann, Friedrich (2014). "Märkte und Anwendungen" [Markets and Applications].Anwendungstechnologie Aluminium[Application technology aluminum] (in German). pp. 9–67.doi:10.1007/978-3-662-43807-7_2.ISBN978-3-662-43806-0.
- ^Guilhaudis, A. (1 March 1975). "Some Aspects of the Corrosion Resistance of Aluminium Alloys in a Marine Atmosphere".Anti-Corrosion Methods and Materials.22(3): 12–16.doi:10.1108/eb006978.
- ^Rambabu, P.; Eswara Prasad, N.; Kutumbarao, V. V.; Wanhill, R. J. H. (2017). "Aluminium Alloys for Aerospace Applications".Aerospace Materials and Material Technologies.Indian Institute of Metals Series. pp. 29–52.doi:10.1007/978-981-10-2134-3_2.ISBN978-981-10-2133-6.
Further reading[edit]
- Hirsch, Jürgen; Skrotzki, Birgit; Gottstein, Günter, eds. (2008).Aluminium Alloys: The Physical and Mechanical Properties.John Wiley & Sons.ISBN978-3-527-32367-8.
- Ghali, Edward (2010).Corrosion Resistance of Aluminum and Magnesium Alloys: Understanding, Performance, and Testing.John Wiley & Sons.ISBN978-0-470-53176-1.