Mechanical alloying during cryomilling of a 5000 Al alloy/AlN powder: the effect of contamination

Elemental powders of 80 vol% 5000 Al alloy (3 wt% Mg) and 20 vol% AlN were milled either in liquid nitrogen or at room temperature under argon. The mi lling of the mixture involved changes in the chemical composition: Fe conta mination, oxidation and in-situ nitridation. The effects of milling time an d temperature on the contamination of the system were analysed. Oxidation a nd in-situ nitridation were characterized by a LECO analyser and thermal de sorption measurements, whereas Mossbauer spectroscopy was used to study the mechanical alloying of the Al alloy. The results show that a metastable so lid solution of Mg and Fe in Al is formed during cryomilling. The occurrenc e of mechanical alloying in spite of the very low milling temperature is in terpreted as a consequence of the fine crystallite size of the Al matrix. ( C) 2001 Elsevier Science B.V. All rights reserved.