Nucleation and growth of quasicrystal-related precipitates within the Al-matrix of AlEr(Fe) alloys

Since the discovery of quasicrystals, their applications to industry have been interesting issues, among which attempts of introducing quasicrystal-related precipitates into the Al-matrix to enhance properties of Al alloys have been made without adequate understandings. Here, we report a formation pathway of quasicrystal-related precipitates in the Al-matrix of an AlEr(Fe) alloy. It is shown that upon thermal aging of the alloy, Al₃Er precipitates form firstly in the Al-matrix, then quasicrystal-related (AlFe)-precipitates may nucleate heterogeneously within the Al₃Er precipitates and grow large. As the quasicrystal-related precipitate grows large, the Al₃Er-precipitate reform as the thin “skin” of the formed composite precipitate, keeping the quasicrystal-related portion well separated from the matrix. Atomic-resolution electron microscopy and spectroscopy reveal that these composite precipitates are the mixtures of the Al₁₃Fe₄ quasicrystal approximant structure and/or quasicrystal-related aperiodic structures, as well as their surrounding skin with Al₃Er-structure. As such, Fe atoms as vexing impurity in Al alloys can be absorbed continuously into such composite precipitates. Our findings provide insights into the feasibility to form quasicrystal-related precipitates in the Al-matrix.