May/June_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 1 8 2 3 using tools designed to form steel. The company found a market for alu- minum ingot in rolling companies that manufactured sheet for end custom- ers. Aluminum was also used for parts in high-end bicycles as well as for mil- itary canteens and tent pegs. How- ever, its use was limited by a lack of high strength and joining and forming technologies. Another significant hurdle facing aluminum development was the pat- ent situation. Inventors and investors on both continents were aggressively using patents and the courts to protect their intellectual property. Only two companies were producing pure alumi- num in the U.S. using the new process and both were spending a great deal of time and resources in court [3] . Outside of the U.S., Héroult’s pat- ent was said to be undisputed because it was submitted first, but according to U.S. patent law in 1886, an inven- tor had to prove that he was first to develop the invention. So, despite the fact that Héroult had filed first in the U.S., Charles Hall was granted the pat- ent due to his meticulous records that proved he had beaten Héroult to the invention. Hall was granted his patent on April 2, 1889. In the rest of the world, it was “first to file” and Héroult pre- vailed. Several licensees of Héroult’s technology were producing alumi- num: Aluminium Industrie Aktien Ge- sellschaft (AIAG) in Switzerland and Germany, British Aluminium Co. Ltd. in the U.K., and Société Electro Métalur- gique Française in France. However, no market for pure aluminum existed and the early interest focused on produc- ing aluminum-bronze alloys for the mil- itary. In Japan, Sumitomo rolled its first aluminum sheet in 1898, but a lack of electrical power hindered development of a strong aluminum industry beyond military applications. Early aluminum sheet technolo- gy was limited to what would now be classified as 1 xxx alloys. PRC alloy 2S (99% min Al, 0.20% Cu), first used in 1888, was the original alloy 1100. In 1906, PRC introduced alloy 3S with 1.2% Mn (modern alloy 3003). Ingots were small (about 50 kg) and produced in steel tilt molds. The ingots had several qual- ity issues including mac- rosegregation, porosity, and a tendency toward severe shrinkage crack- ing with increasing al- loying content. Sheet production was done in very small batches. AUTO INDUSTRY OFFERS A MARKET Stakeholders in the new aluminum industry expected a return on their investments and the automobile industry was about to offer them an early success. On the eve of the 20th century, roads were still unpaved outside of major cities, turn- ing into mud after every rainstorm. Train travel was preferred for comfort and speed. Auto engines were heavy and lacked power, so saving weight ev- erywhere else was a key consideration. Early automakers purchased their bod- ies from coachbuilding companies. The simple open structures, typically without any doors, featured a wood- en spaceframe clad in the lightest suit- able materials such as wood, leather, or even cloth. At this stage in the auto in- dustry, steel sheet was no more ready than aluminum sheet. Neither could be readily formed other than by basic folding, and simple shapes were made using centuries-old whitesmith, or tin- smith, techniques. An upstart auto- maker introduced aluminum sheet in a sports car as early as 1899. It was lighter than wood panels and steel, while add- ing a perceived “high tech” element to the vehicle. Few records exist of the alloys used at that time, but an analysis of a 1951 mudguard from a 1903 Lanchester automobile showed it was made of an alloy sheet with about 0.8% each of Fe and Si, and 0.15% Ti. After almost 50 years of service, it had no visible cor- rosion except for galvanic corrosion in the area where it was joined using cop- per rivets [4] . By 1905, aluminum sheet was rou- tinely used by coachbuilders in Europe and the U.S. The most famous example is the 1907 Rolls-Royce Silver Ghost, en- tirely clad in polished aluminum. Also in 1907, the Pittsburgh Reduction Co. changed its name to Aluminum Compa- ny of America (Alcoa). Detroit became the center of U.S. automobile production, where flush with the success of his Model N, Hen- ry Ford started work on a revolu- tionary new lightweight vehicle, the Model T. The first car shipped in Oc- tober 1908 as a 1909 Model T. It was 225 kg (500 lb) lighter than its main ri- val, the Oldsmobile Model 10, due to the use of vanadium steel and alumi- num. The touring bodies were built by the Pontiac Body Co. and featured aluminum sheet nailed to the wooden spaceframe for the first year of produc- tion. The first aluminum hood shipped on a grey roadster on May 4, 1909 [5] . The same aluminum hood remained in pro- duction with minor modifications until 1914, for a total of more than 500,000 hoods representing 920 tons of alumi- num. The material specifications ap- pearing on the print for the 1913 hood are succinct [6] : << HOOD. SHEET ALUMI- NUM #18B&S.G = .040 >>. The nomen- clature of the specification stands for #18 Brown & Sharpe Gauge, a stan- dard used by jewelers. The steel stan- dard gauge #18 would have been 0.050 in. A new model aluminum hood with louvers appeared in 1915, but a switch to steel appears to have coin- cided with a later insourcing effort. The material callout for the steel hood is a bit more elaborate [7] : << STEEL #24 USS 1907 Rolls-Royce Silver Ghost, entirely clad in polished aluminum.