In aerospace applications, materials with high strength to weight ratios along with properties such as excellent corrosion resistance, lightweight, creep resistance and high thermal strength are needed. Also, cost parameters need to be considered without compromising with quality. In accordance with the properties required; aluminium, titanium, magnesium, nickel and their alloys are mostly used in aerospace industries for making most of its sub components. With a number of beneficial properties, aluminum is an easy choice for manufacturing aircraft.
Aluminum has proven highly versatile throughout history, and continues to do so today. Aluminium and its alloys rank second after iron alloys in terms of scalability. Aluminium is easily processed by forging, stamping and rolling; it is also characterised by low density, and aluminium products are lightweight.
The aerospace industry continues to benefit from the alloy’s properties in order to create safer, more reliable and less expensive aircraft. The use of aluminum alloys reduces the weight of an aircraft significantly. With a weight roughly a third lighter than steel, it allows an aircraft to either carry more weight, or become more fuel efficient. Aluminum’s strength allows it to replace heavier metals without the loss of strength associated with other metals, while benefitting from its lighter weight.
Additionally, load-bearing structures can take advantage of aluminum’s strength to make aircraft production more reliable and cost-efficient. For an aircraft and its passengers, corrosion can be extremely dangerous. Aluminum is highly resistant to corrosion and chemical environments, making it especially valuable for aircrafts operating in highly corrosive maritime environments. This will ensure that aluminum will continue to be a valuable material well into the future.
The production of new light alloys based on aluminum with enhanced characteristics is an urgent task for materials science. The introduction of even a small amount of nanoparticles (less than 1%) can lead to a significant increase in the physical and mechanical properties of inexpensive aluminum alloys. Such compounds will have a lower cost compared to the analogs currently used, where the expensive scandium is used for ligatures. Scientists at TSU view diamond as a promising material for the production of hardened alloys, although other nanoparticles are also used.
There are a number of different types of aluminum, but some are more suited to the aerospace industry than others. Examples of such aluminum include:
2024 — The primary alloying element in 2024 aluminum is copper. 2024 aluminum can be used when high strength to weight ratios are required. Like the 6061 alloy, 2024 is used in wing and fuselage structures because of the tension they receive during operation.
5052 — The highest strength alloy of the non-heat-treatable grades, 5052 aluminum provides ideal expediency and can be drawn or formed into varying shapes. Additionally, it offers excellent resistance to saltwater corrosion in marine environments
7050 – A top choice for aerospace applications, alloy 7050 displays much greater corrosion resistance and durability than the 7075. Because it preserves its strength properties in wider sections, 7050 aluminum is able to maintain resistance to fractures and corrosion.
7068 – 7068 aluminum alloy is the strongest type of alloy currently available in the commercial market. Lightweight with excellent corrosion resistance, the 7068 is one of the toughest alloys presently accessible.
7075 — Zinc is the main alloying element in 7075 aluminum. Its strength is similar to that of many types of steel, and it has good machinability and fatigue strength properties.
At present, aluminium alloys, polymer matrix composites (PMCs) and to some extent titanium alloys constitute the airframes of aircrafts. In the next few decades, the developments in lightweight materials for use as structural members in airframes will most likely continue to be centered upon these three classes of materials. In case of aluminium alloys, minor addition of scandium to conventional aluminium alloys has resulted in unexpected increase in strength, corrosion resistance and weldability. However, the high price of scandium is an inhibiting factor. The availability of cheaper scandium will brighten its use for bulk applications.
The tapping of potential of aluminium-lithium (Al-Li) alloys has been another area of priority. Though first generation Al-Li alloys competed with composites from density and stiffness point of view, it did not find many applications due to problems associated with anisotropy in properties and weldability. Damage tolerant variants of Al-Li with higher fracture toughness and fatigue crack growth resistance have been now developed although at lower strength levels.
High-strength aluminium alloys having non-equilibrium phases – amorphous and quasi-crystalline phase are also being investigated. The possibility of using aluminium alloys processed through powder metallurgy (P/M) route is being evaluated to meet the demands of high temperatures (up to 450°C) for high speed vehicles. While there is confidence on the thermal stability of these alloys at 450°C and ambient temperature properties, mechanisms for retaining these at elevated temperatures is being explored. The challenge with P/M technology would be assuring improved levels of properties coupled with assured reliability and reproducibility.
Nano-sized diamond will improve Aluminium alloys for maritime transport
Nanoscale diamond is a powder of diamonds, with a particle size of several nanometers. Master alloys are auxiliary alloys used to introduce other elements into the liquid metal. In this experiment, they are rods that will later be quite convenient and technologically advanced for use in production.
An experiment on the introduction of nanoscale diamond into an aluminum melt using ultrasonic treatment at the Brunel University (London, United Kingdom) has been completed. “The experiment on the introduction and distribution of nanoparticles in aluminum alloy was carried out in order to understand how to increase the mechanical characteristics of the alloy during technological processing (ductility, weldability, and others) and operation (corrosion resistance), while maintaining the quality,” says Nikolai Kakhidze, a Master’s student at the Faculty of Physics and Engineering.
The experiment showed that the resulting alloy is of high quality, without pores and defects. Thus, the parameters chosen by scientists made it possible to introduce nanoparticles into the alloy without degrading the quality of the starting material; this will further contribute to a significant increase in mechanical properties.
Russian Scientists Create New High-Strength Alloy for Aviation and Auto Industry
Scientists from the National University of Science and Technology MISiS have created new aluminium alloys that are cheap and effective to use in a wide variety of modern vehicles.
The technology for manufacturing thin-walled parts of complex profiles, traditional to engineering, is based on sheet stamping methods. A low metal utilisation rate characterises it, a large number of component units and fasteners (complex parts obtained by stamping, which consist of elements that need to be riveted or welded together). Sheet superplastic forming (SPF), which helps obtain lightweight, solid structures of complex geometry, eliminates these shortcomings.
“We melted the necessary components in a furnace at a temperature of about 800° C and put them in a special mould. Then we temper the ingots and roll them into sheets. At each stage, it is important to control their microstructure, the parameters of which determine the structure of the final sheet after intermediate operations. For this, we use 20 thousand-power microscopes. Then we analyze the properties of alloy samples, their strength and ductility at room temperature as well as at elevated temperatures (400-500°C) by stretching the sample until it ruptures,” Anastasia Mikhailovskaya, the lead researcher, associate professor at NUST MISiS, told Sputnik.
According to her, the implementation of the superplasticity effect in pressure metal treatment allows obtaining parts of complex shape, very close to the final one, during one operation with relatively low-power equipment. Therefore, this helps to reduce the complexity and cost of manufacturing the product significantly. In addition, the method avoids manual punching, bringing the product to a given geometry.
Today, there are several superplastic alloys for SPFs, most of which have meagre strain rates and an elongation of about 300%, Anna Kishchik, a post-graduate student at NISU MISiS, said.
“It takes several hours to mould one piece of medium complexity at such a speed; the cost of the technological process is 70-80% of the cost of the final product. Therefore, reducing the moulding time by several times will increase production volumes and reduce the cost of the product. We offer new alloys capable of high-speed SPF – this reduces the time it takes to get one part to 15-20 min, and the possible degrees of deformation exceeds 400%. These are the properties of our alloy, which is 20-30% more durable than its analogues,” she told Sputnik.
400°C Resistant Aluminium Alloy Created in Russia, reported in Nov 2021
Researchers from the National University of Science and Technology “MISiS” (NUST MISIS) together with fellow Russian scientists have created an inexpensive aluminium alloy that can withstand temperatures 100-150°C higher than its analogues. The scientists responsible for the creation claim that the material would significantly reduce the weight and carbon footprint of new rail vehicles, aircraft and other machinery. Their study has been published in the Journal of Alloys and Compounds.
Aluminium and most aluminium-based alloys are highly resistant to corrosion in almost all environments: the atmosphere, seawater, freshwater, many chemical solutions and most foodstuffs. Given these properties, as well as its low specific gravity and good thermal and electrical conductivity, aluminium is widely used in aircraft, automotive, electronics and other industries.
Aluminium alloy wire could be an effective substitute for the expensive and heavy copper-based conductors used today, the scientists said. Its use in aircraft, high-speed rail vehicles and other equipment would reduce their weight and size characteristics, thereby ensuring significant fuel savings and reducing harmful emissions into the atmosphere. However, the methods of producing such alloys and their element base are extremely expensive and labour-intensive today, NUST MISIS reported.
“Our material has a thermally stable structure and can withstand temperatures up to 400°C. All known aluminium alloys experience significant softening already at 250-300°C. Our alloy includes copper (Cu), manganese (Mn) and zirconium (Zr), which gives a unique combination of electrical conductivity, strength and heat resistance”, Torgom Akopyan, senior researcher at NUST MISIS Department of Metal Forming, noted.
According to the authors of the research, one of the key features of the new alloy is that about 10% of its volume is comprised of special nanoparticles containing zirconium and manganese, which are evenly dispersed in the aluminium matrix. The alloy was manufactured with an electromagnetic crystalliser using the ElmaCast technology developed at RPC Magnetic Hydrodynamics (Krasnoyarsk). Subsequent deformation-heat treatment and analytical studies were carried out with the participation of specialists from the NRC “Kurchatov Institute”. In the future, the scientific team plans to continue working on optimising the chemical composition of the new material and its processing.
Russian Researchers Develop Heat-Resistant Material for Aerospace Industry using Additive manufacturing
Researchers from the National University of Science and Technology MISIS (NUST MISIS) have joined with their colleagues from RUSAL’s Light Materials and Technologies Institute to develop a highly durable alloy using the additive manufacturing method.
Additive manufacturing is a versatile technology that promises to supersede conventional casting methods in the near future. Selective laser melting (SLM) is among the most popular additive manufacturing methods. Aluminium-silicon (Al-Si) alloy components synthesised with SLM technology offer high strength at room temperature, but they do not usually show high levels of strength at temperatures higher than 200 degrees Celsius.
“Porosity and defects, such as hot cracks, balling and un-melted powder, are typical problems when fabricating parts by selective laser melting”, Alexander Churyumov, member of the project team and NUST MISIS assistant professor, told RIA Novosti.
NUST MISIS scientists and their colleagues from the Light Materials and Technologies Institute decided to improve the material’s mechanical makeup by adding new components to the aluminium-silicon (silumin) alloy. “We have further developed the alloy’s chemical composition and SLM parameters so we can guarantee a defect-free structure and the mechanical properties of this new heat-resistant aluminium-silicon-nickel-iron (Al-Si-Ni-Fe) alloy. It is common knowledge that nickel can improve the mechanical properties of Al-Si-Fe alloys by reducing the size of the hardening phases”, Alexander Churymov explained.
The scientists have developed a high-capacity SLM mode for the new alloy; it guarantees an impressive volume density in the synthesised material, for 99.8 percent of the theoretical level. The material owes its high strength to the small structure formed by the Si, Al5Fe (Ni, Cu) and Al3 (Ni, Cu) phases. According to the researchers, the new materials will help in the design of complex shaped parts with optimized geometry for automotive and aerospace technology
Russian scientists test world’s first aluminum engine
Scientists of Novosibirsk State Technical University have tested the world’s first internal-combustion engine fully made of aluminum. The test results will enable scientists to design a smaller engine, Professor of the Aircraft-and Helicopter-Making Chair at the University’s Aircraft Faculty Ilya Zverkov told TASS in Jan 2019.As was reported earlier, the University’s scientists designed the world’s first engine fully made of aluminum and weighing about 200 kg. The engine that uses standard automobile gasoline was expected to be mounted on Yak-52 two-seat planes whose old engines have used up their potential.
The use of aluminum instead of steel has enabled scientists to cut the engine’s weight by 30-40% compared to the standard steel engines of the comparable capacity. At the same time, the new engine’s rated capacity has risen by 40 horsepower to 400 hp while fuel consumption has dropped by about 15%. First flight with Russian hybrid aircraft engine scheduled for 2019
As the University’s press office reports, all the basic details of the new engine will be cast in aluminum in Novosibirsk, which will make it possible to give up imported components that were used in the experimental engine. In a perspective, this will allow using the engine on aircraft of the Russian Air Force.
Earlier, aluminum was already used in aircraft and auto engines but its parts operating under the high load are now made of steel. However, the Novosibirsk scientists have employed the plasma-electrolytic oxidation technology, under which aluminum parts are treated by plasma discharges, which results in a thin layer of aluminum oxide known as the corundum forming on the surface of an aluminum item. The corundum is known for its high firmness and melting temperature and that is why precisely aluminum parts with the corundum surface have made it possible to replace steel items in the engine.