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Laser welding research improves quality of aluminium–copper joints

Engineers at TWI have developed laser welding procedures that greatly improve the quality of welds made between copper and aluminium.

Overcoming material conflicts

When welding most dissimilar metal combinations, a key challenge is the different metals’ chemical incompatibility, which typically leads to the formation of brittle intermetallic phases and, consequently, inadequate weld properties.

To counteract this issue, TWI developed approaches that minimise the formation of these brittle phases for overlap joints of high purity-copper (Cu) and aluminium (Al) thin sheets and plates (with thickness range from 1mm to 6mm).

Applications in vehicle manufacture

The automotive industry could benefit significantly from these developments, as it makes extensive use of Al and Cu in the construction of vehicle batteries. These metals have excellent thermal and electrical properties, which make them ideal for this application.

Individual cell terminals within batteries are connected using busbars, which, along with the terminals, are manufactured from Cu- and Al-based alloys. Consequently, there are numerous monometallic (ie Cu–Cu and Al–Al) and bimetallic (ie Cu–Al) butt and lap joints in a typical battery pack. Current joining solutions, including adhesive bonding and mechanical fastening, are limited in terms of both joint quality and process productivity.

Process development

To minimise the formation of the brittle intermetallic phase between the metals, TWI explored using high-welding-speed processes, which resulted in fast melt and solidification rates, limiting the mixing of metals and leading to significant improvements.

Through this experimentation, TWI has been able to introduce a reproducible procedure which can assist Industrial Members in equipment and process selection for the joining of Cu to Al alloy thin sheets and plates.

For more information, please email contactus@twi.co.uk.

Avatar Paola De Bono Section Manager – Laser and Sheet Processes

Paola De Bono is Section Manager in the Laser and Sheet Processes Section at TWI Ltd. Paola has over eight years of specific experience in laser processing for micro-scale applications, including the welding of highly reflective metals and applications using dissimilar materials.

Having gained her master’s degree in chemical engineering from the University of Palermo in Italy, Paola continued her studies with the Italian Engineering Association, becoming a Chartered Engineer.

Moving to the UK, Paola studied for an engineering doctorate with Birmingham University, where her investigation focused on the topic of ‘Laser Welding of Copper and Aluminium Alloys for electrical Interconnects’.

Originally joining TWI as a Project Leader in 2007, Paola went on to become a Senior Project Leader and then the Team Manager for the Lasers and Sheet Processes section, before becoming the section manager. Her current role involves day-to-day operational management, supporting the delivery of the section strategy, in line with TWI’s corporate plan.

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