Copper-Aluminium Welding: how to overcome industrial barriers?

Copper and aluminium are key materials in electrical and thermal applications. One offers outstanding conductivity: the other is lightweight and cost-effective. But welding them together? That’s where it gets tricky. Metallurgical incompatibilities, galvanic corrosion, limited joining processes… the challenges are real.

Yet with rising copper prices and increasing demands for lightweight solutions in transport and power electronics, industries have no choice: they must learn how to reliably join copper and aluminium.

Which processes can be used? What are the risks? Are there any robust, scalable solutions today? Let’s find out.

Copper-aluminium friction stir welded parts

Copper and Aluminium – Two Metals, Two Behaviours

Copper is an excellent thermal and electrical conductor. It’s easy to shape and remains the industry standard for power and thermal systems.

However, it comes with four key limitations:

  • It’s difficult to weld,
  • Its price is skyrocketing, driven by electrification trends in automotive, energy, data centers and electronic industries: $10,140 per tonne (+80% in 5 years, LME – June 2025),
  • There is a high risk of future shortages,
  • And it’s heavy, which is a major drawback for mobility sectors.

Aluminium, by contrast, is emerging as a strong alternative:

  • It’s lightweight – 3 times lighter than copper,
  • It’s abundant,
  • It’s significantly cheaper: $2,594 per tonne (LME – June 2025),
  • And it conducts heat 5 times better than steel.

Although aluminium is only half as conductive as copper, doubling its cross-section compensates for this loss – while still achieving a 50% weight reduction compared to copper.

Aluminium-copper friction stir weld joint

Copper-Aluminium Welding – Why conventional processes fall short

Copper – A challenging metal to weld

Despite its wide use in industry, copper is inherently hard to weld. Its high thermal conductivity dissipates heat quickly, making it hard to maintain a molten weld pool. On top of that, it oxidises easily at high temperatures, requiring strict gas shielding.

As a result, even well-established methods like TIG or MIG often yield porous or low resistance joints.

Put simply: welding copper to copper is already complex. Welding complex to aluminium? That’s another level entirely. Their melting points differ widely (1085° for copper, 660° for aluminium), they expand differently with heat, and fusion leads to fragile intermetallic phases.

copper pipes for industrial manufacturing use

Processes to avoid

  • Brazing: commonly used but hard to automate and control for industrial production.
  • TIG or MIG Welding: high risk of defects like low resistance and porosity with theses materials.
  • Laser Welding: technically possible, but expensive and difficult to master on hybrid joints.
traditional welding

In short: conventional processes rarely deliver strong, durable Cu-Al joints.

FSW – Reliable, high-performance Cu-Al welding at industrial scale

Friction Stir Welding (FSW) is a game-changer. As a solid-state process, it doesn’t melt the metals. Instead, a rotating tool stirs the materials in a semi-solid state, creating a robust mechanical and metallurgical bond.

Why FSW is ideal for copper-aluminium assemblies:

  • No melting, so no brittle intermetallics,
  • High mechanical strength at the joint,
  • Fully automated and repeatable process,
  • Dissimilar material welding with no filler required.

FSW enables the production of Cu-Al busbars and cold plates with strong, reliable joints – a major step forward for electric vehicles and compact electronic systems.

Friction Stir Welding copper on aluminium

What about galvanic corrosion?

Joining two dissimilar metals can trigger an electrochemical reaction. In humid environments, the less noble metal – aluminium – may corrode rapidly. This is galvanic corrosion.

The good news: it can be effectively managed, provided you:

  • Limit exposure to moisture (sealed or dry condition),
  • Apply surface treatments (insulating coatings, anodising),
  • Design geometries that minimise electrochemical current paths.

Companies like Stirweld already offer proven technical solutions – including specific anti-corrosion protection – for Cu-Al assemblies.

Copper – Aluminium: a winning duo – if you master the welding process

Copper-Aluminium joints are no longer an engineering oddity. They’re a strategic combination: reducing weight, cutting costs and addressing copper scarcity.

But unlocking these benefits depends on mastering the welding technique. FSW stands out as the most promising option – combining reliability, scalability and performance.

copper-aluminium friction stir welded part

Industries already using Cu-Al FSW

Cu-Al FSW isn’t just a lab innovation – it’s already delivering results in demanding industrial sectors:

Automotive & EVs

  • Automotive manufacturers are cutting vehicle weight to improve range. FSW enables lightweight hybrid busbars and cold plates – without compromising conductivity.

Aerospace

  • In aeronautics, Cu-Al FSW is used for power conversion modules and high-power cable assemblies – where weight and mechanical reliability are critical.

Power electronics & renewable energy

  • From solar stations to EV chargers, conductivity and compactness are key. FSW ensures durable, high-performance Cu-Al connections.

Marine mobility

  • In hybrid or electric ships, weight matters. FSW provides corrosion-resistant Cu-Al joints (with appropriate coatings) and high conductivity.

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