Low energy mechanochemical synthesis of (La,Ce,Nd,Pr)(Ni,Al)5

M. RODRIGUEZ; M.R. ESQUIVEL; G. MEYER

Ciudad de Buenos Aires

Congreso; ISMANAM 2008-XV International symposium on Metastable, Amorphous and Nanostructured Materials; 2008

Fernando Audebert-Laura Damonde-Facultad de Ingenieria-UBA

Intermetallics of the AB5-type  can be obtained by mechanical alloying (MA) of either the constituents (elements/alloys) or intermetallics.  The synthesis is quickly and easily achieved in high energy mills. But the process evolution is slower if a low energy mill is used. Therefore, the successive stages of reactive/mechanical milling can be identified and characterized [1]. This behaviour allows a detailed study of the synthesis process and microstructure changes in the material [2,3].    In this work, two AB5’s were mechanochemically alloyed in a low energy mill according to the following route: (La,Ce,Nd,Pr)Ni5 [3,4] + La(Ni,Al)5                   =                    (La,Ce,Nd,Pr)(Ni,Al)5 The synthesis was achieved in a low energy mill under Ar atmosphere. Samples were withdrawn at different integrated milling times and analyzed by different techniques: X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and Energy Dispersive Spectroscopy (EDS). Cell parameter values, crystallite sizes and strain, particles morphology and size distribution during milling were obtained. Phases were quantified by Rietveld analysis. Results were discussed according to the respective milling governing stage. The final intermetallic was obtained after 100 h of milling. The four typical stages of milling were observed and characterized according to chemical homogeneity and particles morphology and size distribution. The shared control of cold welding and fracture is discussed during Initial, Intermediate, Final and Completion stages. Structure evolution and location of elements in the different crystallographic sites is analyzed according to the final phases obtained. Although the recrystallization of the structure was observed by XRD, no defined peaks were detected by DSC during thermal treatments. It was analyzed according to the energy amount supplied during milling. The results were discussed according to the final microstructure obtained. References: [1]  L. Lu, M. O. Lai, Mechanical alloying, Kluver Academic Publishers, 1998, Boston, 1998. [2]  M.R. Esquivel, G. Meyer, Mat. Sc. Forum, 570,  2008, 72-77. [3] M.R. Esquivel, G. Meyer, J. Alloys Compd, 446-447, 2007, 212-217.