ALPDMN PHASE-DIAGRAM IN THE REGION OF QUASI-CRYSTALLINE PHASES

We report results on a metallurgical investigation of the Al-Pd-Mn Phase diagram in the region of the quasicrystalline phase field. Liquidus phase fields have been determined for icosahedral, decagonal and several periodic compounds which are approximant crystals of the quasicrystals. Structure analyses of these phases have been carried out by transmission electron microscopy. As defined from the linear phason strain field theory, the different crystal approximants can be distinguished as belonging either to the icosahedral phase or to the decagonal phase. An equilibrium between icosahedral and modulated icosahedral phases has also been identified. The modulations occur along the threefold icosahedral axes.