Metastable Extensions of Intermediate Phases in Some Aluminum - Rare-Earth Metal Systems

Abstract

ABSTRACTUsing the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10-30 at. pct. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all equilibrium alloy phases [Al4RE (T phase), Al3RE (CN12 close-packed phases) and Al2RE (Laves phase)] have substantial metastable solid solubilities for excess Al; e.g., in the Al-Y system, L phase is extended from 66.7 up to 86 at. pct. Al, suppressing any formation of the Al3RE phase in that system.For early RE elements up to and including Gd, T phase is favored; for alloy chemically intermediate RE elements such as Y, L phase is dominant and for late RE elements (after Ho), the CP phases are extended most. DSC work indicates the formation of additional metastable phases occurring during equilibration.