Metallurgic Expert Knowledge on Titanium:
Titanium alloys retain strength at high temperatures and exhibit low thermal conductivity.
Stainless Steels have a chromium content of at least 12%. It is very reactive from a chemical point of view and is prone to oxidization. The oxide generates a fine, protective skin.
Inconel is a superalloy characterized by a unique combination of high temperature corrosion resistance, oxidation resistance, and creep resistance.
Alpha-Beta (α-ß) Alloys
These alloys feature both a α and ß phase and contain both α and ß stabilizers.The simplest and most popular alloy in this group is Ti6Al4V, which is primarily used in the aerospace industry. Alloys in this category are easily formable and exhibit high room-temperature strength and moderate high-temperature strength. The properties of these alloys can be altered through heat treatment.
Beta (ß) Alloys Beta
Beta (ß) Alloys Beta (ß) alloys contain transition metals, such as V, Nb, Ta, and Mo, that stabilize the ß-phase. Examples of commercial ß alloys include Ti11.5Mo6Zr4.5Sn, Ti15V3Cr3Al3Sn, and Ti5553. Beta alloys are readily heat-treatable, generally weldable, and have high strength. Excellent formability can be expected in the solution treated condition. However, ß alloys are prone to ductile-brittle transition and thus are unsuitable for cryogenic applications. Beta alloys have a good combination or properties for sheet, heavy sections, fasteners, and spring applications.
Metallurgic Expert Knowledge on Aluminum:
2000 series aluminum alloys
Contains 1,9-6,8% copper content and often contains additions of manganese, magnesium and zinc. They are used for forgings, extrusions and liquified gas storage tanks in civil transport and supersonic aircraft. These alloys have lower crack growth rates and thus have better fatigue performance than the 7000 series alloys. Therefore, these are used on the lower wings and body skin.
Commonly used 2000 series alloys are 2224, 2324, 2524.
These alloys are often cladded with 99,34% pure aluminum for increased corrosion resistance.
7000 series aluminum alloys
The Al-Zn-Mg system offers the greatest potential for precipitation hardening though copper is often added to improve stress corrosion cracking resistance (with the drawback of reducing weldability). Stress corrosion cracking resistance decreases with increasing Zn:Mg ratio.
Commercial aluminum-lithium alloys are characterized by their low density, high specific modulus, excellent fatigue, and cryogenic toughness properties.
The marriage of Li and Al reduces density by 3% and increases the elastic modulus by about 6%.
In contrast to new materials systems such as fiber-reinforced composites, low density aluminum alloys do not require large capital investments by the producer in new fabricating facilities.
Metallurgic Expert Knowledge on Composites:
Composite materials are generally composed of soft, tough matrix with strong, stiff reinforcements. Fiber-reinforced polymers are the broad class of composites usually targeted.
Fiber reinforcements are typically:
- Carbon fiber/Graphite fiber (high strength or high modulus)
- Glass fibers
- Ceramic fibers
- Polymer fibers (Kevlar, Polyethylene)
- Tungsten fibers
Polymer Matrix are typically:
- Polyetheretherketone (PEEK)
For decades, the aircraft industry has utilized composite materials in multiple applications, including flight surfaces and some internal cabin parts. Unfortunately, these materials are unique to each design in their fiber layering techniques, resins, and curing processes, which creates great challenges to consistency in manufacturing and assembly.
Composite materials are bonded together to form complex structural sub-assemblies that must be either assembled or attached to other structural components made of aluminum or titanium.
This represents a unique set of challenges that requires radical new tooling technologies.