From Clusters to Nanoquasicrystalline Al-based Alloys

F. AUDEBERT; F. SAPORITI; M. GALANO; P. QUINN

Shangai

Conferencia; International Conference on Rapidly Quenched & Metastable Materials; 2014

The current commercial Aluminium Alloys can be normally used up to at around 250-300°C because the high strength that can be obtained for these alloys at room temperature by ageing heat treatments drop at very low strength values, normally lower than 70MPa at 250°C. Over this temperature in many applications must be used heavier alloys and sometimes over specified alloys with higher cost, such as steels and titanium respectively. Metal matrix composites containing large volume fraction of a second phase, mostly ceramics particles, were developed to increase stiffness and high temperature resistance in order to improve the weakest properties of the Al alloys for structural applications at elevated temperatures. Rapid solidification can be used to refine the microstructure of Al alloys increasing the strength, but also can be used for developing new Al alloys that cannot be obtained by the normal casting processes. During the solidification process the early stages of the cluster formation can determine the microstructure of the new alloy, because at high solidification rate the nucleation process become predominant over the growing process for the microstructure formation. Hence the study of the early stages of the cluster formation can lead to a better design of new rapid solidified Al alloys. Molecular Dynamic Simulation and microstructure characterization of simple binary and ternary Al-based alloys can give the understanding of the cluster forming behaviour of each element in the melt and undercooled liquid of Al rich alloys, which will allow designing alloys with the microstructure and properties required. The development of a nanoquasicrystalline Al-based alloy from the study of the cluster formation in the melt and undercooled liquid till the bulk production is presented. In order to design the alloy theoretical and experimental studies have been performed on liquid and solid state of rapid solidified Al-based alloys. The stability of the alloy also has been studied. The alloy has been manufactured in bulk shape and the mechanical properties were measured at room and high temperature obtaining near 4 times higher strength than the current commercial Al alloys at elevated temperature.