Phase Equilibria in Aluminum Alloy Systems

Phase equilibria in aluminium alloy systems describe the stable combinations of phases that coexist under defined temperature, composition and pressure conditions. Detailed phase diagrams guide alloy design by delineating solid, liquid and intermetallic regions, revealing critical transformations such as eutectic and peritectic reactions. In aluminium-iron alloys, complex intermetallic compounds form with narrow homogeneity ranges, influencing mechanical properties and corrosion resistance. Ternary systems, for example Al-Cu-Fe or Al-Co-Fe, exhibit quasicrystalline and higher-order ordered phases, whose thermal stability and solubility fields are mapped by isothermal sections. Modern investigations integrate high-resolution microscopy, diffraction techniques and thermodynamic modelling to refine phase boundaries and predict diffusion-controlled transformations. Such insights underpin lightweight structural materials, high-temperature coatings and additive manufacturing processes, where control over microstructure and intermetallic formation is paramount for performance and reliability.

Research from Nature Portfolio

Recent studies have elucidated the formation mechanisms of equilibrium and non-equilibrium intermetallic compounds in dissimilar aluminium/steel joints. First-principles phonon calculations combined with kinetic simulations reveal that high pressures favour ductile metastable phases such as Al6Fe, whereas temperature-driven processes predominantly form η-Al5Fe2 and θ-Al13Fe4. Additive manufacturing routes enable fine control over intermetallic sequences, with rapid solidification promoting phases of desired ductility. Machine-learning-assisted structure predictions have clarified the atomic arrangements of Al2Fe and Al5Fe2, improving confidence in non-equilibrium Scheil-Gulliver simulations for joint design.

Phase Equilibria in Aluminum Alloy Systems publication trend

The graph below shows the total number of articles in phase equilibria in aluminum alloy systems across all publications each year (not limited to Nature Index journals).

Technical terms

Phase equilibrium: The condition under which multiple phases coexist at steady temperature and composition.

Intermetallic phase: A compound with a distinct crystal structure formed between two or more metallic elements.

Isothermal section: A slice of a multicomponent phase diagram at constant temperature showing phase fields versus composition.

CALPHAD: A computational approach (Calculation of Phase Diagrams) to model thermodynamic properties and phase stability of alloy systems.

Eutectoid transformation: A solid-state reaction where one phase decomposes into two different phases upon cooling.

References

1. Forming mechanism of equilibrium and non-equilibrium metallurgical phases in dissimilar aluminum/steel (Al–Fe) joints. Scientific Reports (2021).
2. New experimental studies on the phase diagram of the Al-Cu-Fe quasicrystal-forming system. Materials & Design (2020).
3. Experimental investigation of the Al–Co–Fe phase diagram over the whole composition range. Journal of Alloys and Compounds (2020).
4. Phase equilibria among η-Fe2Al5 and its higher-ordered phases. Science and Technology of Advanced Materials (2021).