Short-range order of liquid and amorphous phase in Al-Fe and Al-Ni alloys by means of molecular dynamics simulations

F. SAPORITI; F. AUDEBERT; M. BOUDARD

Boston

Congreso; Gordon Research Conferences; 2011

Amorphous and nanostructured Al-based alloys show improved mechanical properties as compared to the heat-treatable commercial alloys, making it of great industrial interest. Several types of nanostructured Al-based alloys containing a microstructure composed of nanometer-size crystalline and/or quasicrystalline particles embedded in an amorphous or a-Al matrix can be obtained by rapid solidification processes. The microstructure of these alloys is mainly controlled by the short range order (SRO) in the liquid and the nucleation process during the rapid quenching. The present work provides the study of the SRO in the liquid and in the amorphous phase of Al-Fe and Al-Ni alloys by means of molecular dynamics simulation (MDS). The structure was characterized using the partial pair-correlation functions and the bond-angle distribution functions. Cluster analyses at liquid and undercooled liquid states were performed using the Honeycutt-Andersen method. It was observed that amorphous `hase in the Al-Fe alloy has higher fractions of icosahedral clusters than the Al-Ni alloy, even at the liquid state near the melting point. The icosahedral cluster fraction was found increasing as the Temperature decrease. The common-neighbor analysis shows that the fivefold symmetry leads to configurations more complex than the simple icosahedron. The MDS results were compared with the X-ray diffraction analysis of amorphous Al-Fe-Nb, Al-Fe-Ce and Al-Ni-Ce alloys. A clustering model for the amorphous phase of these alloys is presented.