Duralumin dirigible girders (photo from the December 1931 issue of Industrial Heating)

As a result of its unique properties, aluminum has been of key importance in many of the developments of the past century. Why only a century or so? Because although aluminum is the most abundant metallic element in the earth’s crust (8%), metallic aluminum was produced for the first time just 200 years ago. It was not until 1886 that a commercial process was developed – the Hall-Heroult process – to refine aluminum from alumina.

In fact, during aluminum’s first century the metal was so rare it was more valuable than gold by the middle of the 19th century. It was so precious that aluminum bars were displayed with the French crown jewels during an international exposition in 1855. Development and fine-tuning of Hall’s electrolytic process resulted in a reduction in the price of aluminum ingot from $4.86/pound in 1888 to $0.78/pound in 1893.

By the turn of the century, the Wright brothers were looking for a lightweight engine for their aeronautical experimentation. Finding none, a mechanic from their bicycle shop, Charles Taylor, built a 13-HP engine weighing 150 pounds in just six weeks using only a lathe, hand tools and a drill press. The alloy used by Taylor was 92%Al–8%Cu, and an examination in 1985 determined that it was heat treated by precipitation hardening to strengthen the crankcase. In spite of this, Alfred Wilm is credited with developing this heat-treatment process in 1909, leading to the patenting of the Al-Cu alloy, duralumin (see photo).

Due to the need for weight reduction, aerospace applications led the way in the development of aluminum and its alloys. These developments included clad aluminum sheet, forged bearings, hot isostatic pressing and blind rivets. Although composites are making inroads, today’s commercial aircraft are almost 80% aluminum by weight.

Perhaps more surprisingly, early automotive development also significantly utilized aluminum. Aluminum sheet first replaced wood as the body material of choice, although sheet steel soon replaced it. Nevertheless, aluminum was used for the hoods of millions of Model T Fords. World War II and its need for aluminum in military aircraft reduced the availability of aluminum for automobiles. By the end of WWII, just 12 pounds of aluminum was used in the average American car. Due in part to the energy crisis of the 1970s, the amount of aluminum in automobiles (in pounds) has increased every year for the past 34 years to a total of 330 pounds today. A 6-8% fuel savings is obtained for every 10% reduction in weight by replacing steel with aluminum.

Many other industries have utilized aluminum to make their products better. This includes the ship and train-building industries. The S.S. United States, built in 1952 with a lightweight aluminum superstructure, still holds the record for the fastest westbound transatlantic crossing. When the Japanese-made bullet trains switched from steel to aluminum construction, they were able to travel more than 30 MPH faster. Space exploration is another area where aluminum is on the cutting edge of technology.

One of the great icons of Americana is the Airstream trailer. For its entire 70-plus-year history, Airstream has finished its trailers in aluminum. With the help of its manufacturing techniques, extensive testing and the contribution of aluminum, between 65% and 75% of all Airstreams made are still on the road – a testament to durability.

Something we take for granted today is the aluminum beverage can. Only 45 years ago, the first two-piece, drawn-and-ironed can was produced. That same year (1963), Iron City Beer in Pittsburgh was the first to utilize pull-top technology on 300,000 cans. Royal Crown Cola was the first soft-drink producer to utilize all-aluminum cans in 1964. By 1985, aluminum became the most popular beverage package, and the aluminum bottle can was introduced in 2000.

The Aluminum Association is the source of much of the above information. Thanks. IH