Development of Aluminum Wire for Low-Voltage Automotive Wiring Harnesses 2012-01-0925

From the viewpoint of reducing the environmental impacts by automobile emission, improving fuel efficiency is essential. That is why automobiles need to be lightened. However, more and more electrical systems have been necessary in an automobile to ensure safety and comfort. With the increase in the number of electrical systems, the weight of Electrical Distribution System (EDS) also has become increased. In order to reduce the weight of EDS, it was decided to evaluate a change of material from copper to aluminum. In fact, aluminum wires have been used for high-voltage wires, but they have almost never been used for low-voltage wires. SUMITOMO ELECTRIC GROUP developed an aluminum wire that is available for low-voltage wire harnesses and started mass production of the wire from October 2010. In this paper, I'm reporting mainly on our development of a new aluminum alloy that can be used for aluminum wires.

The target properties of the aluminum alloy to be developed were to have a tensile strength of 110 MPa and an electrical conductivity of 58%IACS. We determined the composition of the alloy considering misfit strain. The misfit strain was calculated based on first-principles calculations. The annealing conditions were specified based on a careful study of the precipitation conditions of Al-Fe intermetallic compounds in the aluminum alloy. Under these conditions, we developed a new aluminum alloy with a tensile strength of 120 MPa and an electrical conductivity of 60%IACS, exceeding our targets.

We manufactured aluminum wires of 0.75 to 2.5 mm₂ in size. The wire weight was reduced by 60% compared to that of our conventional copper wires of the same size. The wiring harness weight was also reduced by about 30% using this newly developed aluminum wire.