Isothermal section at 850 °C of the U–Fe–Al ternary system

A systematic investigation of the isothermal section at 850 °C of the U–Fe–Al ternary system was done by means of scanning electron microprobe analysis and X-ray powder diffraction. At this temperature the phase diagram is characterized by the formation of seven ternary phases and two extended ranges of solubility. Three compounds form with non-existing, or negligible, homogeneity domains: UFe2Al10 (YbFe2Al10-type, a=8.9146(3) Å, b=10.1986(3) Å, c=9.0114(3) Å); U2Fe3.6Al13.4 (Th2Ni17-type, a=8.8589(2) Å, c=8.9824(2) Å); and U2Fe12Al5 (Th2Ni17-type, a=8.5631(7) Å, c=8.438(1) Å). Four other phases exhibit more or less extended homogeneity ranges: UFe1+xAl1−x (MgZn2-type); U3Fe4+xAl12−x (Gd3Ru4Al12-type); U2Fe17−xAlx (Th2Zn17-type); and UFexAl12−x (ThMn12-type). The two extended solid solutions, UAl2−xFex and UFe2−xAlx, are formed from the UAl2 and UFe2 binary compounds, respectively, both crystallizing in the cubic MgCu2-type structure.