来源：钛业界

Performance and cost are the two eternal driving forces for the development of material technology, while lightweight, integration, and structural functional integration are common challenges faced by aircraft structural design, material application, and manufacturing technology. In the past few decades, near net forming technologies such as hot isostatic pressing, injection molding, and spark plasma sintering have made significant progress in the field of titanium alloys. However, bottleneck issues such as oxygen content and porosity have not been effectively addressed, which has limited their application in the manufacturing of aviation titanium alloy structures.

From the perspective of scientific exploration and development, modern industry requires structural materials with high strength, fracture toughness, and stiffness, while minimizing weight. Therefore, lightweight and high-strength alloys such as titanium and aluminum, as well as load-bearing and heat-resistant alloys such as Ni based high-temperature alloys, have become the focus of new material research and development plans in various countries. In addition, these materials are also important application materials in laser additive manufacturing.

Advantages and Differences between Titanium and Aluminum Alloys

Titanium alloy has high specific strength, specific stiffness, and good corrosion resistance, meeting the design needs of aircraft for high maneuverability, high reliability, and long service life. Its application level has become an important indicator of the advanced level of aircraft material selection.

Titanium and aluminum alloys are widely used in aerospace, automotive, mechanical manufacturing, and other fields due to their excellent low density and structural strength. Especially in the aviation industry, they play a very important role and are the main structural materials of the aviation industry. Although titanium alloy is about two-thirds heavier than aluminum alloy, its inherent strength means that less amount can be used to achieve the required strength. Titanium alloy has become an important material for reducing fuel costs due to its strength and low density, and is widely used in aircraft jet engines and various spacecraft. Aluminum alloy is currently the most widely used and common lightweight material for automobiles, with a density only one-third that of steel. Research has shown that aluminum alloy can be used up to 540kg in a complete vehicle, which would result in a 40% weight reduction for the vehicle. Audi, Toyota, and other brands' vehicles have all aluminum bodies, which is a good example.

Due to the high strength and low density of both materials, other factors must be considered when selecting alloys.

In critical situations where high strength and low weight are required, every gram is important, but if higher strength components are needed, titanium is the best choice. Therefore, titanium alloys are used in the manufacturing of medical devices/implants, complex satellite components, fixed devices, and scaffolds.

In terms of cost, aluminum is the most cost-effective metal for machining or 3D printing; The cost of titanium is relatively high, but the fuel saved by lightweight parts for aircraft or spacecraft will bring huge benefits, and the service life of titanium alloy parts will be longer.

In terms of thermal performance, aluminum alloys have high thermal conductivity and are often used to manufacture radiators; For high-temperature applications, the high melting point of titanium makes it more suitable, and aviation engines contain a large number of titanium alloy components.

Titanium's corrosion resistance and low reactivity make it the most biocompatible metal and is widely used in the medical (such as surgical instruments) field. Ti64 can also resist salt environments well and is often used in marine applications.

In the aerospace field, both aluminum and titanium alloys are widely used. Titanium alloy has the advantages of high strength and low density (only about 57% of steel), and its specific strength (strength/density) far exceeds that of other metal structural materials. It can produce components with high unit strength, good rigidity, and light weight. The engine components, framework, skin, fasteners, and landing gear in the aircraft are all made of titanium alloy. In addition, referring to relevant materials for 3D printing technology, it was found that aluminum alloys are suitable for working in environments below 200 ℃. The Airbus A380 body uses more than one-third of aluminum materials, while the C919 also extensively uses conventional high-performance aluminum alloy materials. The aircraft's skin, partition frame, wing ribs, and other parts are all made of aluminum alloy.

Titanium alloy has become one of the most expensive metal materials due to its high melting point and difficult to machine properties. However, the lightweight, high strength, and high-temperature resistance of Ti6Al4V titanium alloy have attracted much attention in the aerospace field. Its application scope includes parts such as blades, discs, and casings that operate in the low-temperature section of engine fans and compressors, with a working temperature range of up to 400-500 ℃. In addition, it is also used to manufacture fuselage and spacecraft components, rocket engine cases, and helicopter rotor hubs. However, due to its poor conductivity, titanium is not an ideal choice for electrical applications. Although titanium alloys are relatively expensive, their high temperature and corrosion resistance cannot be replaced by other lightweight metals.

Aluminum based alloys have excellent physical and mechanical properties such as low density, high specific strength, strong corrosion resistance, and good formability, making them widely used in industry. However, from the perspective of additive manufacturing forming technology, aluminum alloy has a relatively low density and poor powder flowability. The uniformity of powder placement on SLM forming powder bed or the continuity of powder transportation during LMD process is poor. Therefore, high precision and accuracy requirements are required for the powder placement/feeding system in laser additive manufacturing equipment.

At present, the main aluminum alloy used in additive manufacturing is Al-Si alloy, among which AlSi10Mg and AlSi12 with good flowability have been widely studied. However, due to the fact that Al-Si series alloys belong to cast aluminum alloys, although prepared using optimized laser additive manufacturing processes, their tensile strength is still difficult to exceed 400MPa, limiting their use in load-bearing components with higher service performance requirements in aerospace and other fields.

Modern aerospace components face a series of stringent requirements, including lightweight, high performance, high reliability, and low cost. This complex structural design and manufacturing is extremely difficult. By innovating and developing laser additive manufacturing technology for typical aluminum, titanium, and nickel based components in aerospace, we can not only achieve lightweight and high-performance material selection, but also reflect the trend of precision and net formability in additive manufacturing technology. By implementing the integrated additive manufacturing of material structure performance, we can apply additive manufacturing technology to major projects in the aerospace field.