The solidification of aluminum-manganese powders

Abstract

The solidification behavior of Al–Mn alloy powders was studied as a function of cooling rate and manganese content. The phases present in the powders differed from those expecied at equilibrium due to competetive nucleation and growth kinetics. The equilibrium Al₆Mn phase was absent due to its relatively sluggish nucleation kinetics, and in the more concentrated and rapidly cooled alloy powders, the metastable quasicrystalline phases were present. Nucleation temperatures measured in alloys cooled at 25°C/s are interpreted to represent formation of the icosahedral phase, which subsequently transforms to the decagonal phase and provides a lower bound estimate of 870°C for the melting point of the icosahedral phase in an Al-30 wt. % Mn alloy.