Rational approximants to the decagonal phase in Al---Mn---M (M = Ni, Cu, Zn) systems

Abstract

A series of alloys (Al₆₀Mn₁₁Ni₄, Al₇₆Mn_15.5Cu_8.5, Al₆₅Mn₁₅Cu₂₀, Al₂₄Mn₅Zn and Al₁₂Mn_2.9Zn) have been prepared in as-cast and rapidly solidified conditions. The occurrence of icosahedral and decagonal quasi-crystalline phases as well as rational approximants to the decagonal phase has been established by electron microscopy. This comparative study highlights the similarities and differences among the closely related crystalline phases serving as rational approximants to the decagonal phase in the three systems Al---Mn---Ni, Al---Mn---Cu and Al---Mn---Zn. Structural features as well as the propensity for twinning of the crystals have been characterized.