Temperature resistance of aluminium sheets

Aluminium sheets are among the most widely used semi-finished products in industrial environments. They are used where low weight, good machinability and sufficient mechanical stability meet changing or permanently elevated temperatures. The practical application range of -50°C to +150°C covers a large proportion of typical industrial applications – provided that design, alloy, sheet thickness and surface are correctly selected.

What matters is not whether aluminium "withstands" high temperatures, but how its properties change under the influence of temperature and what consequences this has for load-bearing capacity, dimensional accuracy and service life.

What does temperature resistance really mean for aluminium sheets?

Temperature resistance in aluminium sheets does not describe the melting point of the material, but the ability to retain its technically relevant properties permanently and predictably under the influence of temperature. In industrial practice, this is less about extreme values than about the question of whether an aluminium sheet reliably performs its function even when it is heated over a prolonged period or repeatedly exposed to temperature fluctuations.

What matters is how mechanical properties change under temperature. As temperature rises, both the yield strength and the modulus of elasticity of aluminium decrease. This does not necessarily mean failure of the component, but it does mean an increasing tendency to deform. Components may deflect more or yield under load, even though they still appear to be adequately dimensioned on paper. These effects must be allowed for in the design.

Another aspect is time-dependent material behaviour. At permanently elevated temperature, aluminium can begin to creep under constant load. This slow, plastic deformation occurs well below the melting point and is particularly relevant for thin sheets, large surfaces or permanent loads. Temperature resistance therefore also means that the geometric shape is retained over the entire service life.

Equally important is dimensional and shape stability under temperature changes. Aluminium has a comparatively high thermal expansion. Even moderate temperature changes lead to measurable changes in length, which, with rigid mounting or unfavourable fastening, can lead to internal stresses, distortion or damage to connections. Temperature resistance therefore always presupposes that these movements are accommodated in a sound design.

Added to this is the behaviour of connections and surfaces. Screwed connections, bonded joints or coatings often react more sensitively to temperature than the aluminium base material itself. Anodised layers or powder coatings on aluminium can lose their optical or functional properties even though the aluminium beneath remains load-bearing. In practice, therefore, it is often not the material but the weakest system element that determines the usable temperature limit.

Aluminium only melts at around 660°C. For industrial use, however, what is decisive is from which temperatures service properties change measurably. The temperature resistance of aluminium sheets is therefore not an absolute value, but the result of material, design, load and duration of use.

Material fundamentals: aluminium and its alloys in the temperature context

Pure aluminium plays hardly any role in industrial aluminium sheet cut to size. In practice, almost exclusively aluminium alloys are used, whose properties are specifically tailored to mechanical load-bearing capacity, corrosion resistance of aluminium and temperature behaviour. What matters here is not only the chemical composition, but also the respective delivery condition of the sheet.

Alloying elements such as magnesium, silicon, manganese or copper noticeably change the behaviour of aluminium under the influence of temperature. Magnesium increases strength and at the same time improves corrosion resistance, which predestines these alloys for many applications in mechanical engineering and vehicle construction. Silicon facilitates machining and improves castability, while manganese increases toughness and stabilises behaviour under changing temperatures. Copper-containing alloys do achieve high strengths, but react more sensitively to corrosion and in some cases show greater property changes under heat.

In addition to the alloy itself, the delivery condition is of central importance. Cold-worked conditions such as H111 or H22 generally behave stably and predictably at elevated temperatures. Heat-treated conditions such as T6 offer high initial strengths, but can lose these more quickly at temperatures above around 100°C. For applications in the upper temperature range, it is therefore necessary to examine carefully whether a high initial strength or behaviour that is as constant as possible over the service life is more important.

The temperature resistance of aluminium sheets is therefore always the result of alloy selection, delivery condition and design. Only the interaction of these factors decides whether a component reliably performs its function over the long term in the temperature range from -50°C to +150°C.

Temperature behaviour at low temperatures (-50°C to 0°C)

Aluminium shows distinctly favourable behaviour in the cold range. In contrast to many steels, no tendency to brittle fracture occurs. Toughness is retained, and in some cases even increases slightly.

Important properties at low temperatures:

• No brittle transition temperature

• Stable elongation properties

• No cracking due to cold

• Consistent machinability

Typical applications in this range are refrigeration and deep-freeze technology, exterior components in wintry climates, vehicle and trailer construction, and protective and cover sheets for sensors and electronics.

Particularly for dimensionally accurate cut pieces, aluminium is a very reliable material here.

Standard application range: 0°C to +100°C

This temperature range represents the ideal working range for aluminium sheets. Mechanical properties remain stable, dimensional accuracy is easy to control, and neither creep nor structural changes play a relevant role.

Aluminium sheets are used here, among other things, for:

• Machine cladding

• Mounting and support sheets

• Enclosures for control and switchgear technology

• Covers, protective hoods and structural elements

In this range there are generally no restrictions with regard to connection technology, surface treatment or continuous load.

Elevated temperatures: +100°C to +150°C

From around 100°C, a continuous but moderate decrease in strength begins in aluminium alloys. This effect is typical of the material and easy to calculate.

Important aspects in this temperature window:

• Yield strength falls more than tensile strength

• Modulus of elasticity decreases slightly

• Permanent loads can promote creep deformation

• Thermal expansion gains importance in design

Up to +150°C, aluminium sheets can still be used reliably with the correct design. Static components, cladding and support sheets without high dynamic load are particularly suitable.

Creep and continuous load under heat

Creep refers to the time-dependent plastic deformation of a material under constant mechanical load at elevated temperature. In aluminium sheets, this effect can occur well below the melting point and is therefore relevant for industrial use as soon as components are exposed to elevated temperatures over a prolonged period.

In practice, creep plays a role above all when aluminium sheets are used in continuous operation close to the upper temperature limit of around +150°C and at the same time have to bear a constant load. Short-term heating or temporary temperature peaks are generally uncritical. Problems arise when temperature and load act together over a long period, since the material can then deform slowly and permanently.

Thin sheets, large-area components and structures with a high surface load are particularly susceptible to creep-related deformation. Unfavourable supports or rigid fastenings can also intensify the effect. To counteract this, sufficient safety reserves should be allowed for, suitable sheet thicknesses selected and, if necessary, alternative materials considered if a permanent high temperature load cannot be avoided.

Thermal expansion and design implications

Aluminium has a relatively high coefficient of thermal expansion. Temperature changes therefore lead to measurable changes in length, which must be taken into account in the design.

Guide value:

– approx. 2.3 mm change in length per metre at a temperature difference of 100°C

Practical solutions are slotted holes, expansion clearances, sliding bearings or floating fastenings. Particularly with large-area aluminium sheets, this point is decisive for service life.

Influence of sheet thickness on temperature resistance

Temperature resistance is influenced not only by the material but also by the sheet thickness. Thin aluminium sheets react more quickly to temperature changes and are more susceptible to distortion or creep.

As a general rule:

• Thicker sheets are more dimensionally stable

• Thin sheets require greater expansion clearances

• High temperatures intensify deflection effects

Surface treatments and temperature limits

The surface often determines up to which temperature aluminium sheets remain optically and functionally stable.

Anodised aluminium sheets are generally permanently stable up to around +120°C. Beyond this, colour changes or stress cracks in the oxide layer can occur.

Powder-coated aluminium sheets are usually limited to +80°C to +120°C in continuous operation, depending on the coating system. Short-term temperature peaks are often uncritical, but continuous loads are not.

For applications close to +150°C, untreated or specially coated aluminium is often the better choice.

Comparison: aluminium, stainless steel and steel in the temperature context

The temperature resistance of a material can only be realistically assessed in direct comparison. Aluminium, stainless steel and steel differ significantly in weight, thermal expansion and strength behaviour under temperature changes.

Property	Aluminium	Stainless steel	Steel
Density	very low	high	high
Temperature range (practical)	-50°C to +150°C	-100°C to +400°C	-50°C to +350°C
Thermal expansion	high	medium	low
Strength decrease under heat	moderate from approx. 100°C	low	low
Corrosion resistance	good to very good	very good	limited
Machinability	very good	limited	good

Aluminium scores above all where weight, machinability and corrosion protection are more important than maximum heat resistance. Stainless steel and steel are superior when high temperatures are permanently combined with high mechanical loads.

Typical aluminium alloys and their temperature behaviour

Not every aluminium sheet reacts in the same way to temperature. In practice, certain alloys are preferred because they show stable behaviour in the range up to +150°C.

EN AW-5754 (AlMg3) is one of the most widely used alloys for aluminium sheets. It offers good corrosion resistance, remains tough even at low temperatures and shows a readily calculable decrease in strength under heat. Ideal for machine cladding, vehicle construction and general structures.

EN AW-5083 (AlMg4.5Mn) has a higher strength than 5754 and shows very good behaviour in the cold. This alloy is preferably used when higher mechanical loads occur or temperature changes are more frequent, for example in special-purpose vehicle or apparatus construction.

EN AW-6061 EN AW 6082(AlMgSi) are heat-treated alloys with high strength in the initial condition. At temperatures above 100°C, however, a greater reduction in mechanical properties can occur. They are well suited for load-bearing components, provided there is no permanent high temperature load.

The choice of alloy therefore decisively determines how safely aluminium sheets can be used in the upper temperature range.

Aluminium sheets in combination with other materials

In practice, aluminium sheets are often combined with steel, stainless steel, plastics or rubber. Under the influence of temperature, additional requirements arise.

Different coefficients of thermal expansion lead to relative movements under temperature changes. If these are not taken into account in the design, stresses arise that can lead to distortion, cracking or loosened connections.

The combination of aluminium and steel or stainless steel is particularly critical. In addition to the different thermal expansion, contact corrosion also plays a role here, which can be accelerated at elevated temperature. Separating layers, coatings or insulating intermediate materials are therefore common.

When combining with plastics or elastomers, their own temperature limits must also be taken into account. A temperature-stable aluminium support is of little use if the attached material already softens or becomes brittle.

When do aluminium sheets reach their limits?

Aluminium is not the right material when:

• temperatures are permanently above +150°C

• high mechanical loads are combined with heat

• minimal thermal expansion is absolutely essential

• aggressive media act at high temperature

In such cases, stainless steel, steel or special high-temperature alloys are better suited.

Practical decision-making aid

To select suitable aluminium sheets, it is not enough to consider only the maximum service temperature. In practice, it is always the interaction of several factors that decides whether aluminium functions reliably in the long term or reaches its limits early.

First, it must be clarified whether this is a short-term temperature load or continuous operation. Short-term temperature peaks – for example from waste heat, solar radiation or process heat – are generally uncritical for aluminium. With permanently elevated temperatures close to +150°C, however, safety reserves must be allowed for.

Another central point is the mechanical load on aluminium sheets. Aluminium sheets are excellently suited for cladding, covers and support sheets with low to medium load. If temperature and load rise at the same time, the topic of creep gains importance. In such cases, greater sheet thicknesses or alternative materials must be considered.

The design itself is also decisive. Thermal expansion must be accommodated in a targeted way. Rigid screw connections without expansion clearance frequently lead to distortion, stresses or cracking under temperature changes. Design measures such as slotted holes, floating bearings or sliding mounts are not a special case with aluminium, but state of the art.

Last but not least, the surface plays an important role. While untreated aluminium is the most robust in terms of temperature, anodised or powder-coated sheets are subject to clear limits. These affect less the load-bearing capacity than above all the appearance and surface integrity.

As a rule of thumb: aluminium sheets are the right choice when weight, corrosion resistance and good machinability are the priority and the temperatures are predictable and manageable. If permanently high temperatures occur in combination with high loads, stainless steel or steel should be included in the assessment at an early stage.

Assessing the temperature resistance of aluminium sheets correctly

In industrial use, aluminium sheets are considerably more temperature-stable than is often assumed. In the range from -50°C to +150°C, they can be used safely in technical terms if alloy, sheet thickness, surface and design are matched to one another.

At low temperatures, aluminium remains ductile and insensitive to cracking. In the standard range up to around +100°C, no relevant restrictions occur. Even at elevated temperatures up to +150°C, use is possible provided there are no high continuous loads or extremely tight dimensional tolerances.

What matters is not to assess aluminium in isolation, but in interaction with load, temperature profile and adjacent materials. If thermal expansion, creep behaviour and surface limits are taken into account in the design, aluminium is a light, economical and permanently reliable material for numerous industrial applications.

Check now whether aluminium is suitable for your temperature requirement – and make a safe material decision for your project!

FAQ

Up to what temperature can aluminium sheets be used? Reliably up to around +150°C in industrial practice, depending on alloy, load and surface.

Do aluminium sheets become brittle at low temperatures? No. Aluminium remains ductile and insensitive to cracking even at very low temperatures.

Does aluminium lose strength permanently under heat? Up to +150°C generally not permanently, provided there is no overageing or continuous creep load.

Is thermal expansion a problem? It must be taken into account in the design, but it is easy to control.

Are coated aluminium sheets temperature-resistant? Yes, but with clear limits. Anodised and powder coatings are limited depending on temperature.