On the nature of the quasicrystalline phases obtained in alloys of Al₈₆Mn₁₄ under slow solidification rates

Abstract

An investigation of the quasicrystalline phases obtained in alloys of Al₈₆Mn₁₄ under slow solidification rates is carried out. A quasicrystalline phase similar to the so-called T phase [L. Bendersky, R. J. Schaefer, F. S. Biancaniello, M. J. Boettinger, M. J. Kaufman, and D. Schechtman, Scr. Metall. 19, 909 (1985)] is found. However, this phase also shows a pseudofivefold axis and a threefold diffraction pattern similar to the same orientation in the reported phase of Al₄Mn. The analysis of pseudofivefold diffraction patterns from different quasicrystalline grains shows elliptical arrangements of spots with different eccentricities. The presence of planar faults indicates the existence of slip pseudoplanes and slip directions in the quasicrystal. Different eccentricities might suggest that some of the reported quasicrystalline phases (T, T′, T″, …, etc.) are structural states obtained from the icosahedral quasicrystalline phase when particular stress environments are acting.