TABLE OF CONTENTS A typical material distribution for a modern commercial airliner, shown in Fig. 2.1, illustrates the heavy dominance of aluminum alloys. The attractiveness of aluminum is that it is a relatively low cost, light weight metal that can be heat treated to fairly high strength levels, and it is one of the more easily fabricated of the high performance materials, which usually results in lower costs. The advantages of aluminum as a high performance material can be summarized:
High strength-to-weight ratio. The high strength 2XXX and 7XXX alloys are competitive on a strength-to-weight ratio with the higher strength but heavier titanium and steel alloys, and thus have traditionally been the predominate structural material in both commercial and military aircraft.
Cryogenic properties. Aluminum alloys are not embrittled at low temperatures and become even stronger as the temperature is decreased without significant ductility losses, making them ideal for cryogenic fuel tanks for rockets and launch vehicles.
Fabricability. Aluminum alloys are among the easiest of all metals to form and machine. The high strength 2XXX and 7XXX alloys can be formed in a relatively soft state and then heat treated to much higher strength levels after forming operations are completed.
Aluminum is also a consumer metal of great importance. In addition to the advantages cited above, other properties of commercial importance include corrosion resistance to natural atmospheres, suitability for food and beverage storage, high electrical and thermal conductivity, high reflectivity, and ease of recycling.
