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.
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.