From the perspective of frontier scientific exploration and development, an article in Science once pointed out that modern industry requires structural materials to possess high strength, fracture toughness, and rigidity, while also being as lightweight as possible. Therefore titanium and aluminum alloy have become key materials in new material development plans of various countries and are also important materials in laser additive manufacturing. Titanium vs Aluminum, what are the differences and advantages of each?
Advantages and Differences Between Titanium and Aluminum
Common Advantages
- Excellent low density
- High structural strength
- Extensive use in aerospace, automotive, and machinery manufacturing
- Significant role in the aviation industry
Differences
Titanium
- About two-thirds heavier than aluminum
- Higher inherent strength allows for using less material
- Widely used in aircraft jet engines and spacecraft
- Reduces fuel costs due to its strength and low density
Aluminum
- Density is only one-third that of steel
- The most widely used material for automotive lightweighting
- Can use up to 540 kg in a whole vehicle, reducing weight by 40%
- Examples of usage include the all-aluminum bodies of Audi and Toyota vehicles
Material properties of aluminum and titanium (Source: protolabs)
| Material | Processing Method | Tensile Strength | Elongation | Hardness |
| Titanium (Ti6Al4V) | SLM | 1186 MPa | 10% | 40 HRB |
| Aluminum (AlSi10Mg) | SLM | 241 MPa | 10% | 45 HRB |
| Aluminum 6061-T651 | CNC | 276 MPa | 17% | 95 HBW |
| Aluminum 7075-T651 | CNC | 572 MPa | 11% | 85 HBW |
| Titanium (Ti6Al4V) | CNC | 951 MPa | 14% | 33 HBW |
Differentiating Factors for Aluminum and Titanium Alloys
Strength/Weight:
- In critical situations, where every gram of a part is important, titanium is the best choice if higher strength is required.
- Titanium alloys are used in manufacturing medical devices/implants, complex satellite components, fixtures, and brackets.
Cost:
- Aluminum is the most cost-effective metal for machining or 3D printing.
- Titanium, though more expensive, can deliver significant value due to the fuel savings from lightweight parts in aircraft or spacecraft and the longer lifespan of titanium alloy parts.
Thermal Performance:
- Aluminum alloys have very high thermal conductivity and are often used to manufacture heat exchangers.
- Titanium’s high melting point makes it more suitable for high-temperature applications, such as in aircraft engines.
Corrosion Resistance:
- Both aluminum and titanium have excellent corrosion resistance.
- Titanium’s corrosion resistance and low reactivity make it the most biocompatible metal, widely used in medical fields (e.g., surgical instruments).
- Ti64 resists salty environments well and is often used in marine applications.
Applications in Aerospace
Titanium Alloys:
- High strength and low density (about 57% that of steel).
- Specific strength (strength/density) is far greater than other metallic structural materials.
- Used for aircraft engine components, frames, skins, fasteners, and landing gear.
Aluminum Alloys:
- Suitable for environments below 200°C.
- Over one-third of the materials used in the Airbus A380 fuselage are aluminum alloys.
- The C919 aircraft also uses a large amount of conventional high-performance aluminum alloy materials.
- Used for aircraft skins, ribs, frames, and wing spars.
Additive Manufacturing of Titanium Alloys and the Aerospace Industry
Industry Growth:
-
- As noted in Deloitte’s “2019 Global Aerospace and Defense Industry Outlook,” the aerospace and defense industries are expected to continue growing, driving increased production demand.
Material Selection:
- Crucial for aerospace and defense applications.
- Reducing the number of components and overall weight is critical for airborne components.
- Every gram of weight reduction brings significant benefits.
Titanium Characteristics:
- High Melting Point: Exceeds 1600°C.
- Processing Difficulty: Difficult to process, contributing to higher costs compared to other metals.
Ti6Al4V Alloy:
- Popularity: Most widely used titanium alloy.
- Attributes: Lightweight, high strength, and high-temperature resistance.
- Applications in Aerospace:
- Engine fan blades
- Compressor discs
- Casings for low-temperature sections of engines (working temperature range: 400-500°C)
- Fuselage and space capsule components
- Rocket engine casings
- Helicopter rotor hubs
Limitations:
- Electrical Conductivity: Poor, making it unsuitable for electrical applications.
- Cost: More expensive than other lightweight metals like aluminum.
Advantages of Additive Manufacturing:
- Reduces processing costs and minimizes raw material waste, providing economic benefits.
Titanium-Based Alloys:
- Among the most systematic and mature alloy systems in additive manufacturing research.
Applications in Aerospace:
- Widely used as load-bearing structures in aircraft.
Case Studies:
- Aero Met Corporation in the United States:
-
-
- Started small-batch production trials of titanium alloy secondary load-bearing structure test pieces for Boeing’s F/A-18E/F fighters in 2001.
- Successfully applied LMD (Laser Metal Deposition) titanium alloy components to the F/A-18 validation aircraft in 2002.
Achievements in Research:
-
- Beihang University (formerly Beijing University of Aeronautics and Astronautics):
- Made breakthroughs in key technologies for titanium alloy laser additive manufacturing.
- Developed large-scale main load-bearing titanium alloy frames with superior mechanical properties compared to forgings, used in aircraft.
Practical Applications:
- Northwestern Polytechnical University:
-
-
- Used laser additive manufacturing to produce upper and lower edge samples of central wing ribs for Commercial Aircraft Corporation of China (COMAC)’s C919 aircraft.
- Dimensions: 3000mm × 350mm × 450mm, Weight: 196kg.
Additive Manufacturing of Aluminum Alloys in Aerospace
Properties of Aluminum Alloys:
- Low density, high specific strength, strong corrosion resistance, and good formability.
- They are widely used in industry as a versatile structural material among non-ferrous metals.
Challenges in Additive Manufacturing:
- Aluminum alloys pose challenges due to their unique physical properties (low density, low laser absorption rate, high thermal conductivity, and susceptibility to oxidation).
- Requires high precision and accuracy in powder spreading/feeding systems in SLM and LMD processes due to poor powder flowability.
Current Aluminum Alloys Used in Additive Manufacturing:
- Primary alloys include Al-Si alloys, with AlSi10Mg and AlSi12 known for good fluidity and extensively studied.
- Despite optimization in additive manufacturing processes, the inherent casting nature limits tensile strength to below 400 MPa, restricting their use in aerospace load-bearing components requiring higher performance.
Development of High-Strength Aluminum Alloys for Additive Manufacturing:
- Intensified R&D globally has led to specialized high-strength aluminum alloys tailored for additive manufacturing.
- Airbus developed Scalmalloy, the world’s first high-strength aluminum alloy powder for AM, with a room temperature tensile strength of 520 MPa, used in A320 aircraft cabin structural parts.
- HRL Laboratories developed 7A77.60L aluminum alloy with a strength exceeding 600 MPa, the first forgeable equivalent high-strength aluminum alloy for AM, now applied by NASA Marshall Space Flight Center in large-scale aerospace component production.
- Domestic innovations include new high-strength aluminum alloys designed by CRRC Industrial Research Institute, surpassing Airbus’ Scalmalloy in print performance with a stable tensile strength exceeding 560 MPa, meeting demands in domestic rail transit equipment and aerospace AM sectors.
Impact and Applications:
- Advancements in high-strength aluminum alloys for AM enable broader applications in aerospace and other high-end manufacturing sectors, including domestic aerospace initiatives adopting these materials for AM applications.
Modern aerospace components must simultaneously meet stringent requirements such as lightweight, high performance, high reliability, and low cost. Additionally, these components are increasingly complex in structure, posing greater challenges in design and manufacturing. Innovations and advancements in laser additive manufacturing (LAM) of typical aerospace alloys like aluminum, titanium, and nickel-based alloys focus on key technologies for shape and property control.
This approach not only reflects the development direction towards lightweight and high-performance materials selection but also highlights the trend towards precision and net-shape manufacturing inherent in additive manufacturing technologies. It enables integrated additive manufacturing of material-structure performance, facilitating significant engineering applications in aerospace.