Phase diagram of the Al-Cu-Fe quasicrystal-forming alloy system -: V.: Solidification behaviour of Al-Cu-Fe quasicrystal forming alloys

The microstructures of as-cast and slowly solidified Al-Cu-Fe ternary alloys in the vicinity of the icosahedral phase region have been investigated using light microscopy and scanning electron microscopy. The chemical composition of the different phases present has been determined by energy-dispersive X-ray spectroscopy with a correction of electron probe microscopy analysis. The solidification process was studied by means of the differential thermal analysis and magnetothermal analysis measurements. In contrast to the equilibrium phase diagram, fast cooling leads to the formation of a metastable beta' phase (an ordered cubic structure) rather than to the formation of the phi phase. The nucleation of omega phase is very sluggish during the solidification. The results are presented as solidification paths, superimposed onto the liquidus surface projection to demonstrate the solidification sequences.