Structural, Thermal and Electrical Properties of Al–Mn Quasicrystals Obtained by Melt Quenching

Abstract

Several kinds of melt-quenched Al–Mn alloys were prepared by a single roller method in order to investigate the structure-sensitive physical properties. By melt-quenching, a large grain size about 1 μm in diameter was obtained. An electron micrograph obtained from such a large grain showed a fivefold symmetry of a quasicrystalline structure, although these alloys contain crystalline Al in the matrix. X-ray diffraction peaks of crystalline Al become smaller with increasing Mn content and no peak was observed at 22.5 at%Mn. The peak intensity of the DTA curves decreases and the transformation temperature becomes higher with increasing Mn content. The electrical resistivity ρ of the melt-quenched alloys is extremely high, reflecting the quasicrystalline structure and the resonance state. The value of ρ increases as the Mn content increases, showing a drastic increase above 20 at%Mn. This behavior is accounted for by the disappearance of crystalline Al phase in the matrix.