Bulk Nanoquasicrystalline Al-Fe-Cr-Based Alloys

M GALANO; F AUDEBERT; M PERES; J KASAMA; C BOLFARINI; C KIMINAMI; W BOTTA FILHO

Congreso; International Conference on Rapidly Quenched and Metastable Materials (RQ13); 2008

Nanostructured Al-based alloys obtained by rapid solidification exhibit high strength compared to commercial Aluminium alloys. Particularly, Al-Fe-Cr based alloys produced by melt-spinning were obtained with a microstructure composed of nanoquasicrystalline particles embedded in an α-Al matrix with excellent mechanical properties. These alloys exhibited high strength at elevated temperatures; nevertheless, the quasicrystalline particles become unstable at high temperature limiting the processing conditions for bulk production and industrial applications. In early works, it had been observed that the use of Nb increased the stability of the quasicrystalline phase delaying the microstructural transformation to higher temperatures [1]. Thus, in order to obtain bulk nanoquasicrystalline alloys for industrial applications new alloys could be processed by means of gas atomisation followed by powder extrusion at elevated temperature. In the present work, two Al-Fe-Cr-based alloys containing low fraction of Nb were produced in a bulk shape as extruded rods from gas atomised powders. The powders obtained were sieved in different ranges of sizes between 25 and 250 μm and the microstructures were characterised by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The microstructure and the different phases obtained are discussed in relation to the chemical composition and the powder size ranges. Powders from both alloys, with sizes in between 25 and 75 μm were extruded at 375°C resulting in rods of 75 mm in diameter. The microstructure of both bulk alloys was characterised; and icosahedral quasicrystals were found in both alloys.