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Aluminum and stainless steel parts for aerospace applications

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. The modern aerospace industry is increasingly using composite materials such as carbon-reinforced polymers and honeycombs 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 its use in many aspects of aerospace production has declined, aluminum is still widely used in modern aircraft. Aluminum remains a strong, lightweight material for many specific purposes. Due to its high ductility, it is easy to machine and relatively inexpensive compared to many composite materials or titanium. It can also be further strengthened by alloying with other metals such as copper, magnesium, manganese and zinc or by cold or heat treatment. When aluminum is exposed to air, tight chemical oxide bonds seal the 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)

7075 is a combination of aluminum and zinc and is the most commonly used alloy in aerospace applications for its 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 final part. While many aluminum aircraft components are purely cosmetic, certain components are critical to the aircraft's function and must have specific characteristics.

One aluminum alloy commonly used in the aerospace industry is aluminum scandium. Adding scandium to aluminum increases the metal's strength and heat resistance. The use of aluminum scandium also improves fuel efficiency. Since it is a substitute for dense materials such as steel and titanium, replacing these materials with lighter aluminum scandium can save weight and thus provide better fuel efficiency.

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 that contain 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 type of stainless steel is graded and indicated by three digits. Although the most commonly used stainless steel is only about one-tenth, there are more than 150 stainless steel models. Additionally, stainless steel can be fabricated into sheets, plates, rods, wire, and tubes, making it useful in a variety of applications. There are five main groups of stainless steels, classified mainly 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 luster 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 505MPa (73,200 psi) versus 310MPa (45,000 psi).

Stainless steel also has a higher shear modulus and melting point than aluminum.

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

Other advantages of stainless steel include its excellent heat resistance and fire resistance, bright, beautiful appearance, and excellent hygienic quality. Stainless steel is also easy to fabricate, 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 space industry has become more diverse over time, modern space 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.

Whether you are looking for high-quality aluminum aircraft or stainless steel aircraft parts, we have what you need. We can help you source various types of aluminum and stainless steel aircraft parts and deliver them with short lead times and competitive prices.