The aerospace industry relies heavily on a few materials including, aluminum, titanium, and Inconel. Each of these metals have unique properties, making them invaluable. How do engineers decide which one to use? In this blog post, we’ll take a look at the properties, advantages, disadvantages, and applications of these three aerospace materials.
Material Properties at a Glance
Here’s a quick glance at the properties of aluminum, titanium, and Inconel.
| Properties | Aluminum Alloys | Titanium Alloys | Inconel (Nickel Superalloy) |
|---|---|---|---|
|
Density (g/cm3) |
~2.7 |
~4.5 |
~8.2-8.5 |
|
Tensile Strength (MPa) |
140-570 |
345-1380 |
690-1400+ |
|
Strength-to-Weight |
High |
Exceptional |
High (especially at high temperatures) |
|
Max Service Temp (°C) |
~250 |
500-600 |
700-1000+ |
|
Corrosion Resistance |
Good |
Outstanding |
Excellent (especially at high temperatures) |
|
Machinability |
Excellent |
Difficult |
Difficult |
|
Raw Material Cost (USD/kg) |
2.2-12 |
5.75-150 |
20-50+ |
|
Recyclability |
High |
High (Complex) |
Moderate (Complex) |
Aluminum
Why use aluminum in aerospace components?
- Lightweight and Strong: Aluminum alloys, particularly 2xxx, 7xxx, and Al-Li series, have high strength-to-weight ratio.
- Cost-Effective: Aluminum is less expensive than both titanium and Inconel. This includes the raw material and the manufacturing costs.
- Manufacturability: Aluminum can easily be machined, welded, and is ideal for high-volume production.
Typical Applications in Aerospace for Aluminum
- Bulkheads, stringers, and stiffeners.
- Fuselage skins and frames.
- Spacecraft tanks (especially Al-Li alloys).
- Wings and control surfaces.
What are the advantages of using aluminum in aerospace applications?
- High specific strength.
- Good fatigue and corrosion resistance.
- Excellent recyclability and sustainability profile.
What are the limitations of aluminum in aerospace applications?
- Temperature Sensitivity: Aluminum loses strength at temperatures above ~150-200° C.
- Corrosion: Notably aluminum alloys in the 2xxx’s and 7xxx’s require cladding or treatments for corrosion protection.
- Formability: High-strength alloys can be more difficult to form or weld.
Titanium
Why use titanium in aerospace components?
- Exceptional Strength-to-Weight: Titanium alloys like Ti-6Al-4V are almost as strong as steel, but weigh 40% less.
- Corrosion Resistance: Forms a self-healing oxide layer, resisting corrosion in harsh environments.
- Formability: High-strength alloys are more difficult to weld and form.
Typical Applications in Aerospace for Titanium
- Fasteners and hydraulic tubing.
- Jet engine compressor blades and disks.
- Landing gear and high-stress airframe components.
- Spacecraft structures and missile components.
What are the advantages of using titanium in aerospace applications?
- High strength-to-weight ratio.
- Fatigue and creep resistance.
- Corrosion resistance.
What are the limitations of titanium in aerospace applications?
- Cost: Titanium is 3-5 times more expensive than aluminum.
- Machinability: It is more difficult to machine and form.
- Wear and Tear: Titanium offers poor surface wear resistances sans treatments.
- Cold Dwell Fatigue: Some alloys can be susceptible and require careful design.
Inconel
Why use Inconel in aerospace components?
- High-Temperature Strength: Inconel 718 and Inconel 625 retain strength and resist creep at temperatures up to 700-1000° C (aluminum and titanium would fail).
- Oxidation and Corrosion Resistance: Resists oxidation and aggressive chemicals at eleveated temperatures.
- Fatigue Reistance: Inconel 718 excels in cyclic, high-stress environments.
Typical Applications in Aerospace for Inconel
- Exhaust systems and heat shields.
- Jet engine turbine blades, discs, and shafts.
- Rocket engine manifolds and thrust chambers.
- Spacecraft fasteners and high-temperature structures.
What are the advantages of using Inconel in aerospace applications?
- Unmatched performance, Inconel responds well in extreme heat and corrosive environments.
- Essential in propulsion systems and critical engine components.
What are the limitations of using Inconel in aerospace applications?
- High Cost: Raw material processing costs are much higher than aluminum and titanium.
- Machinability: Requires specialized tools and processes.
- Weight: Inconel is much denser, if weight is a concern.
Material Trends in the Aerospace Industry
- Aluminum: Still dominant in commercial airframes due to cost. Al-Li alloys are pushing performance.
- Titanium: Gaining market-share in high-performance/next-gen aircraft. Common in engine and landing gear components.
- Inconel: Superalloys, such as Inconel are common in propulsion and engine components.
FAQs
What are aluminum’s properties?
Aluminum is a lightweight, corrosion-resistant metal with excellent thermal and electrical conductivity. It is malleable, ductile, and has a high strength-to-weight ratio, making it an ideal material for a wide range of applications.
What are titanium’s properties?
Titanium is a strong, lightweight metal with excellent corrosion resistance. It has a high strength-to-weight ratio, is highly durable, and is biocompatible, making it ideal for a wide range of applications, including aerospace, medical, and industrial uses.
What are Inconel’s properties?
Inconel is a high-performance nickel-chromium superalloy known for its exceptional heat and corrosion resistance. It exhibits excellent mechanical properties, including high strength, ductility, and fatigue resistance, making it ideal for demanding applications in aerospace, chemical processing, and power generation industries.
