INVESTIGATION OF THE ALUMINUM-RUTHENIUM PHASE-DIAGRAM ABOVE 25 AT-PERCENT RUTHENIUM

Alloys of ruthenium content above nominally 25 at.% were manufactured, investigated using optical and scanning electron microscopy, and anal ysed by EDS, electron spectroscopy, X-ray diffraction and thermal anal ysis. The results indicated that there is a peritectic cascade involvi ng the phases Al3Ru2, Al2Ru and Al13Ru4. Previous work had indicated t hat the last phase in the cascade was Al6Ru, with a eutectic reaction between Al6Ru and Al(Ru). The occasional absence of Al2Ru is explained by the closeness of its formation temperature to that of Al13Ru4, suc h that undercooling can miss the reaction. The phase diagram reactions , formation temperatures and phase widths were modified accordingly.