Al-Fe-Ge: Phase equilibria and new ternary compounds at 400?

The ternary system Al-Fe-Ge was investigated for a partial isothermal section at 400 ?, evaluating the all solid phase equilibria in the Al-rich corner of the system for the first time. Investigations with SEM/EDX were combined with extensive XRD studies using powder-as well as single-crystal techniques. Four new compounds labelled tau(5) to tau(8) were identified and characterized. Complex phase equilibria in the partial section with Fe < 50 at% include all ternary phases from tau(1) to tau(8) with the exception of tau(2) which is replaced by the low-temperature phase tau(5) at 400 ?. The tau(5) phase (Al1-xFeGe1+x) was found to crystallize in a ternary variant of the La2Sb-type (I4/mmm) and was characterized by Rietveld refinements. The compound tau(7) (Al4.5-xFeGe1+x) is related to the beta-phase in the Al-Fe-Si system (Al4.5FeSi). Its crystal structure was determined by single-crystal XRD in space group Cmce. The crystal structures of tau(6) and tau(8) were not determined up to now, but their stability with respect to decomposition into neighbouring phases was confirmed by additional liquid-solid diffusion couple experiments at 470 ?.& nbsp;(c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.0

Automated summary

In this study, the partial isothermal section of the Al-Fe-Ge ternary system at 400 ℃ was investigated, revealing four new compounds and complex phase equilibria. The crystal structures of tau(7) and tau(5) were determined while those of tau(6) and tau(8) remain unknown.