Today, virtually all standard transformer lines from the major manufacturers are wound with aluminum. Although copper wound transformers tend to be smaller than comparable aluminum wound transformers offer some distinct advantages over copper wound units:

Both copper and aluminum oxidize over time. Aluminum conductors oxidize until all exposed aluminum surfaces are covered with  and oxide layer. At that point oxidation stops unless the aluminum oxide barrier is somehow broken and the aluminum conductor is re-exposed to the air. Aluminum oxide inhibits chemical reaction of the metal with the wire insulation. Aluminum oxide is also a good electrical insulator. Copper on the other hand oxidizes completely over time. Copper also acts as a mild catalyst, hastening the decay of the wire insulation. All of these factors combine to give aluminum wound transformers a longer life than comparable copper wound units, typically about five years.  

The heat storage capacity of aluminum is approximately 2.33 times that of copper (specific heat of aluminum is 0.214 cal/gram/°C, specific heat of copper is 0.092 cal/ gram/°C). With aluminum wound transformers having a superior thermal storage capacity than copper wound units, they can withstand more surge and overload currents than copper units (normal exhibited when a motor starts.)

Although the conductivity of copper is better than that of aluminum, on a per pound basis aluminum is over twice as good a conductor as copper.

Nowadays, aluminum foil is widely used in transformer industry, China is one of  the largest aluminum foil producer and comsumer country.In China aluminum foil used for transformers are maily 1050 aluminum foil,1060 aluminum foill and 1070 aluminum foil.In some countries 1100 aluminum foil and 1350 aluminum foil are used in transformer industry too.