Thermal conductivity of aluminium sheets

Aluminium distributes heat quickly and reliably – a decisive advantage in numerous industrial applications. Heat should not only be dissipated but also be able to be distributed in a controlled manner over a surface in order to stabilise components, avoid hotspots and keep processes safe. Particularly in heat sinks, mounting plates, housings or thermally stressed machine components, the choice of the right aluminium sheet plays a central role.

Decision-makers from industry and design therefore need not only rough guide values but a precise understanding of the actual thermal conductivity of various alloys, the influencing factors on thermal performance and the practical effects with cut-to-size pieces. Aluminium offers a very good starting basis for this – provided that the material choice, thickness and surface treatment of aluminium match the technical requirement. Decision-makers from industry and design need precise values, influences and guidance in order to reliably design materials and correctly choose cut-to-size aluminium.

Typical thermal conductivity values of aluminium

Table: thermal conductivity of various alloys

Alloy	Thermal conductivity (W/mK)	Properties	Typical applications
EN AW-1050A (pure aluminium)	approx. 200–230	Very high conductivity, soft, readily formable	LED plates, heat sinks, heat spreaders
EN AW-5754 (AlMg3)	approx. 130–150	Good corrosion resistance, medium strength	Mechanical engineering, housings, vehicle construction
EN AW-6082 (AlMgSi1)	approx. 150–170	High strength, readily millable, stable	Construction, mounting plates, precision parts
EN AW-6060	approx. 160–200	Good conductivity, extrudable	Cooling profiles, electronics
Steel (comparison)	approx. 45–55	Very low conductivity	Structural parts
Copper (comparison)	approx. 380–400	Highest conductivity, heavy, expensive	High-performance heat dissipation

The table clearly shows: aluminium offers an excellent ratio of thermal conductivity, cost and weight. Copper conducts better, but is often not used for reasons of weight and cost.

Thermal conductivity is one of the central properties that make aluminium so valuable in technical applications. For designers, it is not only the pure numerical value that matters but also the question of how heat is distributed, transported and dissipated in a sheet.

Aluminium is one of the materials with very high thermal conductivity. Pure aluminium forms the top class, while alloying constituents gradually reduce the conductivity. This is particularly decisive for the design of cooling surfaces, carrier plates and thermally stressed components.

The thermal conductivity of aluminium is significantly above that of many other engineering materials. The purer the aluminium, the higher the conductivity.

Pure aluminium (EN AW-1050A): approx. 200–230 W/mK AlMg3 (EN AW-5754): approx. 130–150 W/mK AlMgSi1 (EN AW-6082): approx. 150–170 W/mK Copper (for comparison): approx. 380–400 W/mK Steel: approx. 45–55 W/mK

Aluminium is therefore in the upper range, which enables rapid heat dissipation and temperature distribution.

Why aluminium conducts heat so well

The exceptionally high thermal conductivity of aluminium is based on the structure of its metallic lattice, in which electrons can move almost freely. This high electron mobility makes aluminium one of the most efficient heat conductors among common engineering materials. As soon as heat is introduced, the electrons distribute the energy quickly over the entire sheet, thereby compensating temperature differences and preventing local overheating.

A further advantage lies in the uniform heat distribution: while other metals can form thermal hotspots, aluminium ensures a homogeneous temperature field, which protects components from thermal stresses. This property is particularly relevant in mounting plates, in heat sinks or in housings in which electronic components generate heat.

The thermal performance also remains largely stable after mechanical processing such as CNC milling or drilling. Since the metallic bond remains intact, the heat conduction paths are not significantly impaired. In a direct material comparison, the strength becomes particularly clear: aluminium conducts heat about three times better than steel, but is at the same time significantly lighter. This combination of efficiency and low weight makes aluminium a preferred material in numerous industries – from electrical engineering and mechanical engineering through to vehicle construction.

Thermal conductivity at different temperatures

The thermal conductivity of aluminium is temperature-dependent. As temperature rises, the conductivity decreases, but remains sufficiently high for many applications. Typical value development:

• 20 °C: 100 % conductivity (reference)
• 100 °C: approx. 90–93 % of the initial value
• 200 °C: approx. 80–85 %
• 300 °C: approx. 70–75 %

For designers this means: in applications with continuous operating temperatures above 150–200 °C, the design should be made thermally more conservative.

Influencing factors on thermal conductivity

In industrial practice, the pure conductivity value is not sufficient to realistically assess the thermal behaviour of an aluminium sheet. Various mechanical, thermal and materials-related factors influence the effective heat conduction in the component.

Alloying constituents

The influence of the alloy on thermal conductivity is considerable, since every additional alloying constituent changes the microstructure and thus the mobility of the electrons. Magnesium, silicon, manganese or copper do increase strength, hardness and dimensional stability, but at the same time impede electron transport, which noticeably reduces conductivity. Pure aluminium therefore shows the best thermal properties, while structurally optimised engineering alloys deliberately accept compromises in favour of mechanical performance. In practice this means: the more strongly a component's function is geared towards heat dissipation, the higher the purity of the aluminium should be.

Temperature

The thermal conductivity of aluminium changes as a function of temperature, since the lattice structure expands on heating and electron mobility is influenced. Particularly in the range above 150 °C, conductivity decreases more noticeably, even if aluminium continues to conduct relatively well. In applications such as engine covers, housings, energy-intensive systems or LED technology, this temperature-dependent effect must be taken into account in order to ensure stable operating conditions. At the same time, aluminium shows very predictable thermal behaviour, which predestines it for repeated heating cycles.

Microstructure & temper

The microstructure – that is, the internal structure of the metal – determines how freely electrons can move. Fine-grained microstructures generally enable more uniform heat distribution, while coarse-grained structures can amplify local differences. Tempers such as T6 or H111 also influence thermal conductivity, since they change precipitates and dislocations in the material. These act like micro-barriers in the heat flow. In precise applications, for example in optical systems or precision-mechanical components, the choice of temper can therefore decide thermal stability.

Surface treatment

Surface modifications change the heat emission to the environment, because every additional layer has its own thermal resistance. Anodising forms a hard, thin oxide layer that reduces heat emission only slightly but at the same time offers corrosion protection and electrical insulation. Powder coatings have a significantly stronger insulating effect and noticeably slow down heat transfer. In practice, it must therefore be checked whether a decorative or protective surface negatively influences the function of a heat-conducting component. This is critical particularly in heat sinks or mounting plates.

Sheet thickness and cut shape

The thickness of an aluminium sheet influences the type and speed of heat distribution, even if the pure conductivity remains constant. Thin sheets react more quickly to thermal influences, which makes them ideal for dynamic applications in which rapid cooling or heating processes take place. Thick sheets, by contrast, store more thermal energy and distribute it over larger areas, which is advantageous with stable temperature fields and at the machine bed or with base plates. The cut shape also has an effect: long, narrow geometries can distribute heat less well transversely, while compact sheets favour homogeneous distribution. Even the choice of contact surfaces, for example with bolted connections or press-fit assemblies, influences heat flow.

Which aluminium sheet for which purpose? for which purpose?

• Electronics, LED, heat sinks: pure aluminium 1050A or conductive alloys such as 6060/6082 for rapid heat dissipation.
• Mechanical engineering: 5754 and 6082 for stable, reliable thermal behaviour combined with good strength.
• Vehicle and special-purpose vehicle construction: aluminium for unit plates and structural components due to its low mass and effective heat conduction.
• Mounting plates, housings, power distribution: uniform temperature distribution and low internal stresses through large-area heat distribution.

Heat conduction in practice: what to look out for with cut pieces

For real-world use, not only the conductivity values are relevant but also all factors that have an influence during processing, assembly or operation.

• Thickness: influences the energy capacity and determines how stable the temperature field remains.
• Dimensional accuracy: flat bearing surfaces are of decisive importance in cooling applications.
• Surface: a smooth, untreated surface conducts better than a layer with an insulating character.
• Processing: milling, facing and drilled holes can shorten or lengthen local heat paths.
• Distortion: one-sided heating can deform sheets – important with precision components.

In addition, the type of fastening plays a role. Bolted connections, press fits or adhesive bonds influence heat dissipation at contact points and should be considered in the design.

Limits of aluminium in heat dissipation

Although aluminium has a very high thermal conductivity, the material reaches natural limits in certain areas of application. At temperatures above about 200 to 250 °C, aluminium gradually loses strength and dimensional stability, which restricts its use in heavily thermally stressed environments. In addition, despite its higher weight and significantly higher cost, copper remains the more efficient heat conductor, particularly when it comes to maximum dissipation performance in a confined space.

The risk of local overheating must also not be underestimated: if heat is introduced at a single point and cannot be dissipated quickly enough via the component, temperature peaks arise which, despite the fundamentally good conductivity, can lead to stresses or distortion. In addition, coatings such as anodising or powder coating act as additional thermal resistances, since they insulate the surface and slow down heat transfer. These factors should be taken into account in the material selection and the design of heat-stressed components in order to ensure permanently stable and reliable function.

Decision aid: which aluminium sheet for which purpose?

For selecting the right aluminium sheet, it is not only the pure conductivity that counts but the interplay of alloy, thickness, surface and later function in the component. For applications with high heat dissipation such as LED modules or electronic assemblies, alloys such as 1050A, 6060 or 6082 are particularly suitable, since they distribute heat quickly over the surface and avoid hotspots. In mechanical engineering or with precision parts, 5754 and 6082 are increasingly used because they offer a reliable combination of stability and thermal performance. In vehicle construction, weight and controlled heat conduction play a greater role; here 5754 and 6082 are frequently used, while the surface is often anodised to prevent corrosion.

For mounting plates or machine beds that require a calm and balanced temperature field, the use of 6082 or 5083 in greater thicknesses is recommended. For housings, power engineering or covers – where heat must be dissipated moderately but structural stability must be ensured at the same time – 5754 and 1050A are suitable. The decision therefore depends to a decisive extent on whether maximum heat conduction, mechanical stability, corrosion protection or the most uniform possible temperature distribution is the priority.

Concluding consideration

Aluminium sheets combine exceptionally good thermal conductivity with low weight, high machinability and solid mechanical stability. This combination explains why they are used as the preferred material for thermally stressed components in almost all technical sectors. However, it is crucial not to consider a project's thermal requirements in isolation but always to evaluate them in interplay with the choice of alloy, sheet thickness, surface condition and mechanical requirements. Only in this way can it be ensured that a sheet not only dissipates heat reliably but also remains dimensionally stable in the long term and does not build up unexpected stresses.

Particularly in applications with high heat concentration – such as LED technology, power electronics, mechanical engineering or vehicle construction – it becomes clear how strongly the material choice influences the service life and performance of a system. Anyone who determines early on which thermal properties are required can use aluminium optimally and design cut-to-size pieces so that heat is distributed evenly, components are protected and processes are kept stable. Aluminium thus becomes not only a functional component but an active part of the overall thermal architecture.

Are you planning a project with defined thermal requirements? Check now which aluminium sheet and which thickness is suitable for your application – and order your precisely fitting cut piece directly online.

FAQ

Which aluminium alloy conducts heat best? Pure aluminium (1050A) has the highest thermal conductivity. Engineering alloys are slightly below it.

Does anodising reduce heat conduction? Yes, slightly – the oxide layer has an insulating effect.

Is aluminium better than copper? Not in heat conduction, but it offers a better ratio of weight, cost and machinability.

Which thickness is suitable for cooling plates? Thinner sheets react more quickly, thicker ones distribute heat more evenly – depending on the component.

Does the cut piece play a role? Yes, particularly flat contact surfaces and clean processing are decisive for good heat transfer.