Formation processes of the ω-Al70Cu20Fe10 phase synthesized by SPS technique

Abstract

The ω-Al70Cu20Fe10 phase formation processes have been investigated for two types of samples synthesized by Spark Plasma Sintering: model samples with planar Al/Al-Cu-Fe interfaces produced from Al and icosahedral i-Al-Cu-Fe powder beds superimposed in a graphite die and Al/Al-Cu-Fe composites. For reactively sintered model samples, the ω-Al-Cu-Fe phase formation was studied using Field Emission Scanning Electron Microscopy coupled with Energy-Dispersive X-ray spectroscopy. In-situ Field Emission Scanning Electron Microscope with a heating stage was used to observe the microstructure evolution of initial Al/i-Al-Cu-Fe composites from room temperature up to 823 K. Observations and chemical analyses performed on the different types of samples show the presence of secondary phases such as θ-Al2Cu and AlCu together with the presence of an eutectic microstructure which indicate the formation of a transient liquid phase, during the formation of the ω-Al-Cu-Fe phase.The formation processes of the ω-Al-Cu-Fe phase suggested in this work highlight two different scenarii involving the Al enrichment of pre-existing i-Al-Cu-Fe particles and the filling of initial porosities via a liquid mediated reaction involving θ-Al2Cu and AlCu intermediate phases.