Crystallization of the AlMn icosahedral phase

Abstract

Differential scanning calorimetry (DSC) measurements of the crystallization kinetics of the icosahedral phase (i-phase) in Al_xMn_100−x alloys for 78 ⩽ x ⩽ 90 are presented. Transmission electron microscopy (TEM) investigations show that for x > 82, the i-phase occurs as dendrites that are surrounded by α-Al. For x<82, the decagonal phase appears in competition with the i-phase and completely replaces it by x=78. For one composition, Al₈₆Mn₁₄, the transformation kinetics and morphology were studied by electrical resistivity and DSC measurements, TEM and X-ray diffraction. The non-isothermal DSC data are fit using a numerical model. From these fits, we present crude estimates of the activation energy for the diffusion of aluminum in Al₆Mn and a lower bound on the i-phase, Al₆Mn interfacial energy.