Metallic bipolar plates for polymer exchange membrane (PEM) fuel cells are currently manufactured by
stamping of thin sheets. However, there are dimensional and shape errors of microchannels because of
forming limitation such as spring back of thin sheets after stamping. On the other hand, stamping
process is limited to commercially available sheet alloys, which restricts the development of a high
corrosion resistant substrate aluminum alloy. Here, thixoforming (a commercial semisolid route) that is
applicable to a wide range of aluminum alloys is proposed for net-shape micromanufacturing of
aluminum bipolar plates with high dimensional stability. High corrosion resistance cast A356 (Cu-free)
and wrought AA7075 (~2% Cu) aluminum billets are used for this study. Initial billets are heated at
different semisolid temperatures. Subsequently, the semisolid slurries are injected into the die cavity.
A356 and AA7075 aluminum bipolar plates are successfully fabricated by thixoforming with very small
deviation of 0.7% and 1.5% from the nominal value of 0.300 mm in the microchannel depth, respectively.
A multilayer coating of TiN/CrN is deposited on the surface of thixoformed bipolar plates through a
commercially available magnetron sputtering technique. Electrochemical corrosion tests show that
coated-thixoformed A356 (Cu-free) bipolar plates have significantly lower corrosion current densities
than coated-thixoformed AA7075 (~2% Cu) bipolar plates. This seems to be due to the deleterious effect
of Cu alloying element on the corrosion resistance of aluminum alloys that clearly confirms the
importance of substrate material development for corrosive PEM fuel cell environment. It is suggested
that specific high corrosion resistance aluminum alloy for PEM fuel cell application can be simply
designed and then thixoforming can be efficiently and cost effectively employed to fabricate net-shape
aluminum bipolar plates.