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.
