AMAG CROSSALLOY® FOR SPACE
Well-equipped for harsh environments
Aluminium alloys are indispensable in space technology. Their excellent mechanical properties combined with low weight make them a preferred material for structural components, tanks, modules, and other key elements in both manned and unmanned space missions. In space, where every kilogram adds to payload costs, the use of lightweight materials is essential. The high strength-to-weight ratio of aluminium is further enhanced by alloying with elements such as copper, magnesium, zinc, and silicon. Alloys containing these elements exhibit the highest mechanical strength values, excellent toughness, corrosion resistance and good formability. Their high thermal conductivity makes aluminium alloys especially effective in managing the extreme thermal environments in orbit.
This property mix makes aluminium an excellent candidate primarily for structural components of space systems. In this regard, satellites often use 6xxx- and 7xxx-series aluminium alloys for their frames and panels. Manned space capsules such as the Orion capsule utilize aluminium structures reinforced with carbon-fiber-reinforced polymers (CFRP) for added strength and thermal stability. Aluminium is also used in support structures for solar panels and in precisely machined payload adapters, combining low mass with mechanical rigidity. Moreover, high-strength aluminium-lithium alloys are employed too in rocket tanks and external structures due to their excellent mechanical properties and weight efficiency. Some of the most used alloys in aerospace include 2195 (Al-Li), 2024 (Al-Cu-Mg), 7075 (Al-Zn-Mg-Cu) and 6061 (Al-Mg-Si).
Environmental and Radiation Challenges in Space
The extreme conditions of the space environment subject materials to multiple degradation forces as shown in Figure 1.Rapid thermal cycling - from extreme cold in the shadow of a planet to intense solar heating - causes significant thermal expansion and contraction. These shifts can induce thermal stresses, potentially leading to microcracks over the course of a space mission. The space vacuum also promotes outgassing of gaseous contaminants in metals, alloys and coatings affecting both material performance and durability of onboard instruments. Another key environmental factor is space weather. Space weather encompasses solar particle events (SPEs), galactic cosmic rays (GCRs), and solar wind, which can contribute to the degradation of spacecraft materials. Solar particle events can deliver high-energy protons and electrons capable of inducing displacement damage and ionization in structural components. Prolonged exposure to galactic cosmic rays - which consist of high-energy heavy ions originating outside the solar system - can have cumulative effects, altering the microstructure of materials at the nanoscale. Particularly thin metal coatings with thicknesses ranging from a few to several hundred micrometers suffer greatly under these harsh conditions. These processes can trigger electronic malfunctions, surface erosion, and long-term embrittlement.
Corpuscular irradiation can cause atoms in the aluminium matrix to be displaced from their lattice positions, forming vacancies. This displacement damage degrades mechanical performance by creating stress concentrations and disrupting load transfer mechanisms as well as alterations in thermal and electrical conductivities.Precipitation-hardened aluminium alloys are particularly affected by radiation effects since these alloys rely on the presence of finely dispersed secondary phases for their mechanical strength. Under exposure to solar irradiation, these precipitates can dissolve, coarsen, or transform into different, less effective hardening phases. This leads to reduced hardness, strength, and corrosion resistance. The increased atomic mobility caused by radiation-induced vacancies accelerates the diffusion of alloying elements, sometimes resulting in unwanted phase formations at grain boundaries, which can promote embrittlement and intergranular corrosion.Microstructural changes due to radiation translate into macroscopic performance degradation. In T6 temper conditions, for example, the loss of strengthening precipitates results in a notable decrease in yield strength and hardness. Ductility may be compromised due to radiation-induced microcracks or the formation of coarse phases, and corrosion resistance can diminish as new intermetallic phases form. Creep resistance also declines due to enhanced dislocation movement facilitated by radiation.
Potential Mitigation Strategies and Research Insights
Improving radiation tolerance in aluminium alloys intended for space applications is an essential focus in aerospace materials engineering.
For aluminium alloys the most effective strategy involves the use of overaged tempers such as T7, which enhance the stability of hardening precipitates and reduce their susceptibility to dissolution under radiation. Unlike peak-aged conditions (T6), where finely dispersed strengthening particles are more vulnerable to radiation-induced transformations, T7 conditions foster larger and more thermally stable precipitates that are less prone to disruption.A more recent approach to increase the stability of the hardening phase is to change the nature or type of the phase itself. By carefully designing the alloy composition and aging treatments, engineers can promote the formation of precipitates such as the T- Mg32(Zn,Al)49-phase, which exhibits superior stability under irradiation. These stable phases act as barriers to dislocation movement and can maintain structural integrity even in high-radiation environments where a high number density of vacancies is present.
New Research Insights: Irradiation resistant AlMgZn crossover alloys
Recent research - which was conducted by researchers at the Montanuniversität Leoben in collaboration with AMAG demonstrated that by combining beneficial traits from the 5xxx (Al-Mg) and 7xxx (Al-Zn) series, crossover alloys with enhanced radiation resistance can be developed. A newly engineered AlMgZn alloy containing 4.7 wt% Mg and 3.4 wt% Zn exhibited remarkable microstructural stability when exposed to heavy ion irradiation up to 1 displacement per atom (dpa), which corresponds to the effect of a major sun storm. The key strengthening phase (T-Mg32(Zn,Al)49) remained structurally stable. Unlike traditional Mg2Si phases in AlMgSi alloys (such as 6061), which tend to dissolve under similar radiation exposure, T-phase in this crossover alloy showed no significant morphological changes or dissolution, even at high doses. No cavities or major damage were observed either.The high-volume fraction and chemical complexity of the T-phase appears to be a decisive factor in achieving radiation tolerance. In contrast, particles rich in Cr, Fe, and Mn were more susceptible to radiation-induced dissolution, as confirmed by EDX mapping and transmission electron microscopy (TEM).
AMAG CrossAlloy®.57 for Space Applications
As reported in previous editions of the AluReport AMAG is heavily investing in the industrialization of the crossover alloying concept. Rigorous testing of numerous trial lots in different thicknesses and tempers revealed great potential for application in many different fields such as automotive, transportation, defence, machining and others.Based on the indications on improved radiation resistance of T-phase-hardened alloys gathered on alloy samples manufactured on laboratory scale, in-depth characterization on the microstructure of industrially produced sheets and plates was initiated and is currently still in progress. Preliminary results gathered in TEM investigations in pristine or pre-irradiation condition (Figure 2) confirm the existence of T-phase particles in both 1mm and 3mm samples. Compared to the results gained on lab-scale samples (Figure 2, Literature) the hardening precipitates in industrial samples are significantly smaller but the general morphology is comparable.Since the results of post-irradiation characterization are still pending, the radiation resilience of AMAG CrossAlloy.57 remains to be fully proven, but the indications are more than promising. In the meantime, further development of the thermomechanical treatment is ongoing.
Conclusion
Despite the harsh conditions of space, aluminium alloys remain preferred materials in aerospace applications due to their versatile properties. However, radiation exposure poses significant challenges, especially for precipitation-hardened variants. Key to success is the long-term stability of strengthening phases and the targeted reduction of radiation-induced defects. Future material solutions must combine lightweight performance with enhanced resistance to cosmic radiation.Even though the final assessment is still pending, we are confident that AMAG CrossAlloy®.57 has the potential to be established as a new-generation space material. As material selection is usually based on a multitude of mechanical and technological demands, results from testing show good performance in these regards too.
Customer advantages
In contrast to most commercially available aluminium alloys, the unique microstructural features and the resulting irradiation resistance make AMAG CrossAlloy.57 an ideal candidate for space applications. Especially for long-duration missions, where durability is a crucial factor, T-phase hardened material could be superior to most of its competitors. Also, general aviation could benefit from utilizing AMAG CrossAlloy.57. Even though less extensive compared to space, heavy ion irradiation is also a contributing factor to material degradation at cruising altitudes of long-range commercial aircrafts.raft.
Sources:
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