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Neutron diffraction study of mechanically alloyed and in situ annealed Al75Mo25 powders

Enzo, Stefano and Frattini, Romana and Canton, Patrizia and Monagheddu, Marzio and Delogu, Francesco (2000) Neutron diffraction study of mechanically alloyed and in situ annealed Al75Mo25 powders. Journal of Applied Physics, Vol. 87 (6), p. 2753-2759. eISSN 1089-7550. Article.

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DOI: 10.1063/1.372251

Abstract

The mechanical treatment of a Al75Mo25 mixture of pure elemental powders in a high-energy mixer mill induces partial solid state reactivity and solid solution formation. This is suggested by a quantitative phase evaluation and by the changes of Al lattice parameter carried out with Rietveld analysis of diffraction patterns collected after extended time of processing (4, 8, 16, 32, 57, and 78 h). The small angle neutron scattering experiments showed that diffusion processes are the rate-controlling step for these solid state reactions. The formation of metastable phases is confirmed by in situ neutron diffraction annealing experiments on selected as-milled powders. In the specimen mechanically alloyed for 4 h, Al12Mo phase is formed at 590 °C (below the aluminum melting point). Soon after this temperature, the remaining Al is consumed to form the Al8Mo3 phase. In the alloy mechanically treated for 32 h, the Al12Mo phase appears after annealing at 430 °C, while the Al8Mo3 phase is found at 493 °C. After the disappearance of Al12Mo phase (500 °C), the solid state reaction proceeds to form a new tetragonal Al3Mo phase, not reported in the equilibrium phase diagram. In the specimen mechanically treated for 57 h, the total formation of Al8Mo3 is recorded at 430 °C. Conversely, in the powder ball milled for 78 h, the Al8Mo3 phase appears at 390 °C and coexists with tetragonal Al3Mo.

Item Type:Article
ID Code:642
Status:Published
Refereed:Yes
Uncontrolled Keywords:Aluminum-based nanocrystalline materials, mechanical alloying (MA), Al-Mo system, powder metallurgy
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
Publisher:American Institute of Physics
eISSN:1089-7550
Publisher Policy:Depositato in conformità con la politica di copyright dell'Editore
Deposited On:18 Aug 2009 10:02

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