Cryomilling of Al/AlN powders

Elemental powders of 80 vol% 5000 Al-alloy (3 wt.% Mg) and 20 vol% AIN were milled in different mechanical conditions and at three different temperatures tin liquid nitrogen (cryomilling), low temperature (about -50 degrees C) and room temperature). The effects of these parameters on the milling efficiency of Al and AlN and on the mechanical alloying were investigated. The cryomilling of both Al and AlN resulted in a rapid decrease in size of the coherently diffracting domains (<50 nm). However, a good homogeneity of the mixture was obtained only after 6 h of milling. The differential scanning calorimeter (DSC) measurements and the EDS analyses have shown that mechanical alloying of the Al-3 wt.% Mg alloy had occurred. The absence of variation of the Al lattice parameter, measured by X-ray diffraction (XRD), is interpreted as a consequence of Fe diffusion from the milling balls into the Al matrix. (C) 1999 Elsevier Science S.A. All rights reserved.