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When creating parts for aerospace applications, there are many factors to consider, such as part shape, weight, and durability. These factors all affect the flight value of the aircraft. For many years, the material of choice for aerospace applications has been aluminum. However, in modern jets it only accounts for 20% of the structure.

However, the use of composite materials such as carbon-reinforced polymers and honeycomb materials is increasing in the modern aerospace industry due to the need for lightweight aircraft. In recent years, aerospace manufacturers have begun researching alternatives to aluminum, one of which is aerospace-grade stainless steel. The use of this stainless steel in new aircraft components has increased. This article will explain the uses and differences between aluminum and stainless steel in modern aircraft.

Aluminum is a relatively light material, weighing approximately 2.7 g/cm3 (grams per cubic centimeter). Although aluminum is lighter and less expensive than stainless steel, aluminum is not as strong and corrosion resistant as stainless steel. Stainless steel is superior to aluminum when it comes to durability and strength.

Although aluminum use has declined in many aspects of aerospace production, aluminum is still widely used in modern aircraft. Aluminum remains the strongest and lightest material for many specific purposes. Due to its high ductility, it is easy to machine and it is relatively inexpensive compared to many composite materials or titanium. It can also be further strengthened by alloying it with other metals such as copper, magnesium, manganese and zinc or by cold or heat treatment. When aluminum is exposed to air, tight chemical oxidation bonds isolate aluminum from the environment. This feature makes it extremely corrosion resistant.

The most popular aluminum alloys used to make aerospace parts include:

Aluminum alloy 7075 (aluminum/zinc)

Aluminum alloy 7475-02 (aluminum/zinc/magnesium/silicon/chrome)

Aluminum alloy 6061 (aluminum/magnesium/silicon)

Aluminum processing parts

7075, a combination of aluminum and zinc, is the most commonly used alloy in aerospace applications, offering excellent mechanical properties, ductility, strength and fatigue resistance.

7475-02 is a combination of aluminum, zinc, silicon, and chromium, while 6061 contains aluminum, magnesium, and silicon. Which alloy is required depends entirely on the intended application of the tip. While many aluminum aircraft parts are purely decorative, certain parts are essential to the function of the aircraft and must have specific characteristics.

One aluminum alloy commonly used in the aerospace industry is aluminum scandium. Adding scandium to aluminum increases the strength and heat resistance of the metal. The use of aluminum scandium also improves fuel efficiency. Since it is an alternative to denser materials such as steel and titanium, replacing these materials with lighter aluminum scandium can save weight and thus improve fuel efficiency.

Stainless Steel Parts for Aerospace Applications

Stainless steel may seem like a surprising choice compared to aluminum in the aerospace industry. Despite its greater weight, stainless steel has recently seen an increase in its use in aerospace applications.

Stainless steel refers to a family of iron-based alloys containing at least 11% chromium, a compound that prevents corrosion of iron and provides heat resistance. Different types of stainless steel include the elements nitrogen, aluminum, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum. The types of stainless steel have been graded and represented by three digits. Although the commonly used stainless steel is only about one tenth, there are more than 150 stainless steel grades. Additionally, stainless steel can be fabricated into sheet, plate, rod, wire, and tubing, making it suitable for a variety of applications. There are five main groups of stainless steels, classified primarily by their crystal structure. These groups are austenitic, ferritic, martensitic, duplex and precipitation hardening stainless steels.

As mentioned above, stainless steel is an alloy composed of steel and chromium. The strength of stainless steel is directly related to the amount of chromium in the alloy. The higher the chromium content, the stronger the steel. It has been found that the use of stainless steel alloys increases aircraft components that require high strength but can handle the added weight. Stainless steel has high corrosion resistance and high temperature resistance, making it suitable for a range of aerospace components, including actuators, fasteners and landing gear components.

benefit:

Although stronger than aluminum, stainless steel is usually much heavier. However, stainless steel parts have two main advantages over aluminum:

Stainless steel has high corrosion resistance.

The resistance of stainless steel to iron oxide is due to the presence of chromium in the alloy, which forms a passive film to protect the material from corrosion. Whether from atmospheric conditions or chemical solvents, stainless steel is highly resistant to corrosion. Due to its protective oxide layer, stainless steel protects against oxidation and corrosion. In fact, the membrane can actually repair itself when exposed to oxygen. Corrosion and stain resistance, low maintenance and a familiar gloss make stainless steel a common material in applications requiring strength and corrosion resistance.

Stainless steel is stronger and more wear-resistant.

Stainless steel has a higher tensile strength than aluminum and can better withstand stress, vibration, scratches, impact and damage. For example, grade 304 stainless steel has a higher ultimate tensile strength than aluminum at 505 MPa (73,200 psi) versus 310 MPa (45,000 psi).

The shear modulus and melting point of stainless steel are also higher than that of aluminum.

These properties are critical to many aerospace parts and make stainless steel parts a versatile choice for aerospace applications.

Other advantages of stainless steel include its excellent heat and fire resistance, bright, beautiful appearance and excellent hygienic qualities. Stainless steel is also easy to manufacture, an important consideration when all parts of an aircraft must be welded, machined or cut to precise specifications. Finally, certain stainless steel alloys have extremely high impact resistance, which is an important factor in the safety and durability of large aircraft.

 In conclusion

As the aerospace industry has become more diverse over time, modern aerospace vehicles are more likely to be constructed with stainless steel airframes or fuselages. Although more expensive, they are also much stronger than aluminum and, depending on the grade used, can still provide an excellent strength-to-weight ratio.