Understanding the formation of (Al,Si)3Sc and V-phase (AlSc2Si2) in Al-Si-Sc alloys via ex situ heat treatments and in situ transmission electron microscopy studies

•Effect of Sc additions to Al-Si (6xxx series Al-alloys) was shown to be profound.•(Al,Si)3Sc nanoprecipitates in Al-Si-Sc alloys result in significant hardening.•Rod-shaped V-phase (AlSc2Si2) formed was deleterious to mechanical properties.•Multiple orientation relationships of V-phase with aluminium were determined.•In situ TEM heating used to study precipitation mechanisms of Sc-containing phases.