Formation of Al–Fe–Si glass that grows from the melt through a first-order transition

► Microstructures of rapidly solidified Al–Fe–Si alloys demonstrate formation of a glassy phase, which we term q-glass, that is not a kinetically frozen liquid. ► The phase grows from the melt by a first order phase transition in the manner of a crystal, but scatters as a metallic glass. ► In this paper, by studying a large number of Al–Fe–Si alloys (8–22at% Fe and 5–20at% Si), we confirmed this observation and identified domains of formation of the q-glass, as well as a 1/1 α-cubic approximant and an icosahedral phase. Microstructures of rapidly solidified Al–Fe–Si alloys demonstrate possible formation of a glassy phase, which we term q-glass, that is not a kinetically frozen liquid. Microstructural observations point out that the phase grows from the melt by a first order phase transition in the manner of a crystal, but scatters as a metallic glass. In this paper, by studying a large number of Al–Fe–Si alloys (8–22at% Fe and 5–20at% Si), we confirmed this observation and identified domains of formation of the q-glass as a primary phase, as well as a 1/1 α-cubic approximant and an icosahedral phase. Our attempts to grow such a glass in different metallic systems by substituting Fe with Ni and Co have not succeeded. We discuss several reasons why the Al–Fe–Si system might be unique.