Quasicrystal Decomposition in Nanoquasicrystalline Al-Based Alloys

MARINA GALANO; FERNANDO AUDEBERT; BRIAN CANTOR; IAN STONE

Simposio; Ismanam 2006; 2006

Nanoquasicrystalline Al-based alloys have microstructures composed of nanoquasicrystalline particles embedded in an α-Al matrix, and have high strengths at elevated temperatures. However, the metastability of the quasicrystalline phase can limit the use of these alloys at elevated temperatures. In previous work, it was observed that the use of Nb or Ta increases the stability of the quasicrystalline phase, delaying microstructural decomposition to higher temperatures [1]. These alloys could have promising applications at elevated temperature (up to 400°C) in the automotive and aeronautical industries. Therefore it is of great importance to understand the evolution of the alloy microstructures with temperature. In the present work the decomposition of quasicrystalline particles of melt-spun Al93(Fe3Cr2)7, Al93Fe3Cr2Nb2 and Al93Fe3Cr2Ta2 (at%) alloys was studied by means of in-situ hot-stage transmission electron microscopy (TEM). The melt-spun alloys were characterized by means of X-ray diffraction and TEM, and phase chemical analysis was performed using energy dispersive X-ray spectroscopy in a scanning-transmission electron microscope. Quasicrystal dissolution was observed in the three alloys studied, and the alloys containing Nb or Ta showed a perictectoid transformation as well. The different quasicrystal decomposition processes and the decomposition temperatures are discussed as a function of alloy composition.