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Microstructure development in as-cast Al-Mg-Li alloy

Since the beginning of economical crisis, weight reduction and temperature stability, as well as high strength and stiffness, have become the key driving forces for new material development and utilization in aerospace and space industry. One of the more promising materials to be utilized is aluminium-magnesium-lithium alloy due to combination of high strength and light weight as well as the god weldability, and corrosion resistance. While, every 1% of lithium added to aluminium increases elastic modulus roughly for 3 GPa and decreases density by approximately 80 kg/m3, the exact influence of magnesium on the phase precipitation and strengthening of Aluminium-Magnesium-Lithium ternary system is not fully understood. The aim of this investigation is to identify the Mg influence on microstructure development of Aluminium- Magnesium-Lithium alloy in as cast condition. The results of preliminary metallographic testing conducted on Al-2, 5wt.%Mg- 0, 72wt.%Li produced under laboratory conditions have shown existence of two different secondary phases, T(Al2LIMg) and Al3Mg2 in αal. While optical microscopy shows existence of phases precipitated in interdendritic areas and grain boundaries, electron microscopy allows for them to be localised based on differences in magnesium and aluminium content. Ultimately, T has been identified to precipitate in interdendritic areas, whilst Al3Mg2 will precipitate at drain boundaries of last solidifying areas.

Al-Mg-Li alloy, lithium, magnesium, phase precipitation, microstructure

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