SEM study of quasi-crystallized Zr₆₅Cu_12.5Ni₁₀ Al_7.5Ag₅ amorphous alloy at initial stage

Microstructure evolvement during crystallization process for the melt-spun Zr₆₅Cu_12.5Ni₁₀ Al_7.5Ag₅ amorphous alloy has been studied by DSC analysis and TEM. We monitor the crystallization process by DSC, and stop at given temperatures, following by cooling down from these temperatures in the DSC furnace to examine the corresponding microstructure evolvement by TEM. The results show that the crystallization of Zr₆₅Cu_12.5Ni₁₀ Al_7.5Ag₅ alloy can be divided into three stages. At the initial stage, an icosahedral quasi-crystal (I-phase) is formed as primary phase from the amorphous matrix without apparent compositional variation. In comparison with the amorphous matrix, the I-phase is Zr-rich and Cu-poor slightly with high nucleation and growth rates by consuming the amorphous matrix, leading to a microstructure with closed packed grains at the first stage of crystallization. However, the residual amorphous phase still exists at this stage.