Improved Al–Y–Fe glass formation by microalloying with Ti

Abstract

We demonstrate that the sequence of phases formed upon annealing rapidly quenched Al88Y7Fe5 alloys is a sensitive function of the sample preparation conditions. Materials that show X-ray diffraction patterns typical of amorphous metallic alloys are actually partially nanocrystalline in some cases. Isothermal differential scanning calorimetry (DSC) studies of alloys with glass-like X-ray diffraction patterns demonstrate that an exothermic peak observed in non-isothermal DSC scans typically associated with glass crystallization is actually due to coarsening of nano-sized grains of α-Al. However, alloys prepared with small additions of Ti (Al88- x Y7Fe5Ti x with x = 0.5, 1 or 2) are amorphous. The crystallization temperature increases with increasing concentrations of Ti. Experimental data indicate that Ti is not simply a scavenger of internal O but may enhance local ordering in the undercooled alloy, stabilizing the liquid against the nucleation of the α-Al phase.