A study on the solidification behaviour of Al–Cr–La alloys in the aluminium-rich region

Abstract

Abstract 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 (0.03–2.0 at%) and La (0.03–1.0 at%) contents were produced using an arc melter. After annealing at 600 °C for 600 h, 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, the first series of alloys (samples A–E with varying Cr contents) 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. Second series (samples F–J with varying La contents), 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.