Introduction
Aluminum, with its excellent balance of lightness and strength, is an indispensable material in diverse fields such as automobiles, aircraft, and building materials. In recent years, driven by global trends in decarbonization and electrification, the demand for even lighter and stronger alloys has been rapidly increasing. This article will detail the latest technology trends and practical examples, focusing on the three main themes of “weight reduction,” “high strength,” and “new alloy development.” Through each chapter, we will clarify the key points for technology selection with an eye on manufacturing costs and mass producibility, and also touch upon diversification strategies for overseas procurement. From the next section, we will first explore the forefront of weight reduction technology.
Latest Technology Trends in Weight Reduction
Improving Specific Strength with Nanocrystallization
In recent years, “nanocrystallization” technology, which refines the crystal grains of aluminum alloys to several hundred nanometers or less, has been gaining attention. By reducing the crystal grain size from the conventional 10μm range to about 100-500nm, it is possible to increase the tensile strength from 300 to over 350MPa while achieving weight reduction with almost no change in specific gravity. The fine crystal grain boundaries impede the movement of dislocations, contributing to increased strength during plastic deformation, but optimizing yield and process costs remains a future challenge.
Utilization of Magnesium-Containing Alloys
Magnesium (Mg) is the second lightest metal after aluminum and also contributes to strength improvement. Therefore, Al-Mg alloys (5xxx series) with an Mg content of 3-5wt% are widely used as lightweight materials. The addition of Mg improves specific strength by 10-15%, and their use is advancing in structural components for aerospace and EV bodies. Although corrosion resistance is slightly reduced, practical problems can be overcome by combining it with appropriate heat treatment and surface treatment.
Shape Optimization with 3D Printing (SLM/EBM)
Metal 3D printing technologies such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM) can produce parts with hollow structures or topology-optimized shapes in a single piece, which was difficult with conventional casting or forging. By additive manufacturing with a layer thickness of 20-50μm, high rigidity can be maintained while keeping the wall thickness to the necessary minimum. Cases have been reported where weight was reduced by 20-30% compared to conventional methods due to increased design freedom. For mass production application, improvements in powder reuse rates and build speeds are required.
The Forefront of High-Strength Technology
Grain Boundary Control (Grain Boundary Strengthening Technology)
The most fundamental approach to increasing strength is strengthening through grain boundary control. The finer the crystal grain size, the more the dislocation movement at the grain boundaries is impeded, and the tensile strength improves (Hall-Petch effect). In particular, Continuous Dynamic Recrystallization (CDRX) allows for the achievement of both excellent toughness and high strength because low-angle grain boundaries (LAGBs) gradually transition to high-angle grain boundaries during the high-stacking process, forming a uniform fine microstructure (ResearchGate). Furthermore, continuous and discontinuous dynamic recrystallization (DDRX, GDRX) that occurs during processes like warm rolling and hot compression are also utilized, and there are cases of achieving tensile strengths of 300MPa or more through appropriate process design (ScienceDirect).
Hot Isostatic Pressing (HIP) and Recrystallization Treatment
Hot Isostatic Pressing (HIP) is a technology that holds materials at high temperatures under an isotropic gas pressure of tens to hundreds of MPa to close and eliminate casting pores and internal defects, while also densifying the structure. For example, reports show that HIP treatment of Al-Si-Mg alloys (around 75MPa, temperature 550-600°C, for several hours) reduces the cooling rate requirement for the supersaturated solid solution in the quenched state, while reducing internal porosity by over 90% and improving fatigue strength and yield strength by 10-20% (MDPI). Furthermore, it is also possible to draw out high-strength properties exceeding 400MPa by optimizing the precipitation hardening structure through solution treatment and artificial aging performed after HIP. A major feature is that HIP itself involves dynamic recrystallization (DRX), allowing the “recrystallization treatment” of forming a uniform fine microstructure while removing defects to be achieved in a single process (ScienceDirect).
Surface Strengthening Treatment: Advanced Coatings like AlooH®
In addition to the internal strength of the base material, advanced surface treatment technologies are indispensable for improving the fatigue durability of the part surface. AlooH® uses only steam and forms a uniform, high-hardness oxide film while controlling the chemical reaction between the steam and the base material inside a high-temperature, high-pressure vessel. Compared to conventional anodizing, there is no variation in film thickness due to electrode distance or electrolyte concentration irregularities, and a uniform film can be achieved even on complex-shaped parts, significantly improving pitting corrosion resistance and wear resistance. Furthermore, test data has been reported showing that AlooH® treatment also modifies the microstructure of the base material surface, forming a fine oxide layer and a highly crystalline region near the surface, which improves both tensile strength and fatigue limit values by 10-15%. Its ability to achieve both high corrosion resistance and high strength makes it optimal for surface strengthening of automotive and aircraft parts.
Trends in New Alloy Development
High-Performance Alloys for Aircraft and Automobiles
In the aircraft and automotive fields, there is an urgent need to develop new alloys with a higher specific strength (strength-to-density ratio) than conventional ones from the perspective of improving fuel efficiency and reducing operating costs. Recent research has reported alloys that achieve both a tensile strength of over 400MPa and a 15% or more improvement in specific strength by optimally blending copper (Cu), magnesium (Mg), and silicon (Si) and controlling fine precipitates. In particular, Al-Cu-Li series alloys developed for aircraft are being evaluated for their ability to reduce the specific gravity from the conventional 2.8g/cm³ to about 2.6g/cm³ by adding Li, while maintaining high fatigue strength, and their application is expanding to automotive engine parts and structural materials.
Aluminum Alloys Specifically for 3D Printing
With the spread of metal 3D printing technology, special alloys that emphasize suitability for forming with SLM/EBM have also appeared. For example, Al-Si-Mg series alloys suppress thermal strain during melting by containing about 12-15wt% of Si, reducing internal stress during additive manufacturing. Also, by controlling the recrystallization behavior through the addition of Mg, the decrease in strength in the stacking direction is suppressed, and mechanical properties of 300MPa or more are achieved even for large parts with a height of about 100mm. Thus, composition design that balances powder characteristics and resistance to thermal history is promoting the practical application of 3D printed parts.
Composite Alloys with Enhanced Corrosion and Wear Resistance
Metal Matrix Composite (MMC) alloys, which have enhanced corrosion and wear resistance for use in harsh environments such as coastal structures and machine parts, are also attracting attention. A typical technology involves dispersing 5-10vol% of ceramic fine particles such as SiC or Al₂O₃ in an Al alloy matrix, which has been confirmed to improve tensile strength and hardness by over 30% and more than double the wear resistance. Furthermore, a major advantage is that by concentrating the hard phase near the surface, local wear progression can be suppressed while maintaining the overall light weight.
Domestic and International Case Studies
Application in Aircraft Structural Members
In aircraft, weight reduction of the airframe directly leads to improved fuel efficiency and range performance. New-generation aluminum-lithium (Al-Li) alloys, especially 2198-T8 and 2196-T8511, are attracting attention because they can improve specific strength by 15-20% compared to conventional aircraft aluminum alloys while reducing the specific gravity from about 2.8 to 2.6 g/cm³. In fact, these alloys have been adopted for fuselage skin and wing spar applications, and effects of reducing annual fuel consumption by tens of thousands of liters have been reported (ROSA P). Furthermore, according to the latest statistical analysis, the introduction of Al-Li alloys is expected to improve fuel efficiency by up to 10% annually for the entire aircraft, also contributing to the reduction of environmental load (Number Analytics).
Cost Reduction Case Study in Automotive Parts
In the automotive field, the case of Ford’s F-150 pickup truck switching its entire body to aluminum from the 2015 model is famous. This reduced the vehicle weight by 14% and significantly improved fuel efficiency from the conventional 14 mpg to 22 mpg (city/highway combined) (ICCT). The fuel cost reduction effect is equivalent to saving about 200 gallons (approx. 750 L) per 10,000 miles (approx. 16,000 km) of annual driving, and assuming a gasoline price of $3/gallon, a cost reduction of about $600/year can be expected. In addition, the vehicle weight reduction reduces component wear and the load on the drivetrain, suppressing maintenance costs and succeeding in lowering the total cost of ownership (TCO) (Materials Education (MatEdU)).
Expansion into the Construction and Infrastructure Fields
In urban construction and infrastructure, the use of building-integrated photovoltaic (BIPV) facade modules with aluminum as the base material is increasing, replacing conventional glass and steel panels. Recent research has reported a case where BIPV modules using aluminum back panels reduced weight by 30% compared to glass modules of equivalent output, and reduced installation and support structure costs by about 15% (ScienceDirect). Furthermore, by combining them with anodizing and powder coating, which have excellent corrosion and weather resistance, long-term maintenance costs can also be significantly suppressed. Due to these advantages, their application is advancing to high-rise building exteriors, bridge walkway railings, and temporary structures for disasters.
Challenges and Future Outlook
Balancing Cost and Mass Producibility
The more advanced the technology, the stricter the manufacturing processes and processing conditions become, and cost increases are a challenge. For example, in nanocrystallization, specialized equipment investment and high-precision control are essential for high-energy processing (such as mechanical alloying or high-speed shear processing) to refine crystal grains to 100-500nm, and there is a risk of reduced yield and insufficient throughput. In the future, the key to achieving a balance will be cost reduction through the introduction of continuous processes and in-line quality control, and shortening of cycle times by optimizing heat treatment cycles.
The Need for Supply Chain Diversification
The development of high-performance alloys requires a stable supply of Li, Cu, and rare elements, but these are subject to geopolitical risks and price fluctuations. For example, although the specific strength improvement effect of Al-Cu-Li series alloys is high, because the global demand and supply of Li raw materials are limited, it is necessary to form alliances with multiple domestic and international suppliers and to expand the use of secondary raw materials (recycled materials).
Direction of Next-Generation R&D
In the future, it is expected that high-speed alloy design using “inverse design” (Materials Informatics) with AI and prediction of fine precipitation behavior by quantum chemistry simulation will become mainstream. For example, research is underway to optimize the interaction between powder properties and thermal history in Al-Si-Mg alloys specifically for 3D printing using multivariate analysis, and it is expected to contribute to achieving both additive manufacturing quality and mechanical properties. Furthermore, with the practical application of real-time microscale monitoring technology, process control before the occurrence of defects will become possible, and the development of next-generation high-performance aluminum alloys is expected to accelerate.
Conclusion
In this article, we have looked at ① weight reduction technologies that reduce weight by 20-30% through structural optimization with nanocrystallization, Mg-containing alloys, and 3D printing, ② high-strength methods aiming for over 400MPa with grain boundary strengthening, HIP + artificial aging, and AlooH® coating, and ③ the trend of new alloy development that achieves improved corrosion and wear resistance with Al-Cu-Li series, 3D printing-specific alloys, and MMCs. Also, from case studies in the aircraft, automotive, and construction fields, the effects of technology application, such as a fuel efficiency improvement of around 10% and TCO reduction, have been confirmed.
In the future, the market is projected to grow at a CAGR of about 5% from 2025 to 2030, with a particularly sharp increase in demand for high-performance aluminum for EV and aerospace applications. Balancing cost and mass producibility, diversifying the supply chain, and introducing Materials Informatics will be key, and the competition for rapid practical application of next-generation alloys will intensify further.
Sources:
- Ministry of Economy, Trade and Industry “Statistics on Exports and Imports of Metal Products” (https://www.meti.go.jp/)
