A Study on the Solidification Behaviour of Al-Cr-La Alloys in the Aluminium-Rich Region

This study examines the solidification behaviour of Al-Cr-La alloys, reflecting the increasing use of rare-earth elements to enhance the properties of aluminium alloys. The research aims to determine how the new ternary phase Al ₂₀ Cr ₂ La, formed by the addition of La, influences the solidification process. This fundamental understanding is essential before these alloys can be developed for high-performance applications. Ten alloys with varying Cr and La contents were produced using an arc melter. After annealing, their solidification and microstructure were analysed using DSC and SEM. In alloys with higher Cr content, solidification begins with the Al ₄₅ Cr ₇ phase, followed by the ternary Al ₂₀ Cr ₂ La phase, then (Al), and finally a mixture of (Al) + Al ₁₁ La ₃ . Thus, these samples (A–E) exhibit four phases: Al ₄₅ Cr ₇ , Al ₂₀ Cr ₂ La, (Al), and Al ₁₁ La ₃ . (Al) is present in the matrix and mixed with Al ₁₁ La ₃ , while the ternary Al ₂₀ Cr ₂ La phase is observed around the binary Al ₄₅ Cr ₇ phase. In samples F–J, solidification also begins with the binary Al ₄₅ Cr ₇ phase, followed by the ternary Al ₂₀ Cr ₂ La phase and (Al), and finally the (Al) + Al ₁₁ La ₃ mixture. In this case, the microstructure of samples with increased La content (F–J) consists of the ternary Al ₂₀ Cr ₂ La phase, the (Al) + Al ₁₁ La ₃ mixture, and an (Al) matrix.