Ion induced metastable phases

We have investigated the formation of crystalline, metastable phases in metallic alloy systems by use of ion beam mixing techniques. Equilibrium phases with two atoms/cell such as CsCl structures or solid solutions can be formed as well as metastable amorphous alloys. Al-based alloys Al/Pd, Al/Fe and Al/Zr represent examples of systems which exhibit different behavior under irradiation. Extended solid solutions and CsCl structures are formed in Pd/Al. Both Al/Fe and Al/Zr at compositions of 80 at.% Al form amorphous alloys under room temperature irradiation and transform to metastable structures under elevated temperature ion irradiation or thermal annealing. Al80Fe20 transforms to the quasicrystalline icosahedral phase and Al80Zr20 to an ordered cubic. Both systems transform to the stable phase Al3M when annealed at 400°C. Further, irradiation of multilayer structures at 200°C results in a direct transformation to the metastable phase.