Short communication Microstructure evaluation of Al–Al 2 O 3 composite produced by mechanical alloying method S.M. Zebarjad * , S.A. Sajjadi Department of Materials Science and Metallurgical Engineering, Engineering Faculty, Ferdowsi University, Mashhad, Iran Received 21 September 2004; accepted 23 December 2004 Available online 22 February 2005 Abstract Mechanical alloying process using ball-milling techniques, has received much attention as a powerful tool for fabrication of sev- eral advanced materials, including amorphous, quasicrystals, nanocrystalline and composite materials, etc. This research is focused on production of Al–Al 2 O 3 composite materials by mechanical alloying method and on investigation of its microstructure. For this purpose a horizontal ball mill was designed and manufactured. Aluminum and alumina powders, with specified size and weight per- cent, were added to the mill. The mixed powders were milled at different times. The milled powders were pressed and sintered under argon gas control. Microstructure of produced composite was investigated by scanning electron microscope. The results show that increasing milling time causes to make fine alumina powders as well as uniform distribution within aluminum, also in steady-state stage increasing milling time has not significant effect on their size distribution within aluminum. The results of atomic analysis of initial and milled powders at different times show that at the beginning of milling, the powders will tend to absorb iron and gradually their susceptibility decrease until steady-state condition is prevailed. The result of infrared spectroscopy does not show any evidence of compounds except alumina. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Composite; Alumina; Aluminum; Mechanical alloying 1. Introduction In 1960s mechanical alloying (MA) technique was used for production of an oxidation resistant alloy. Dur- ing recent years using this technique for production of vast variety of alloys has been suggested. In fact mechanical alloying process using ball-milling and/or rod-milling techniques, has received much attention as a powerful tool for fabrication of several advanced materials, including equilibrium, non-equilibrium (e.g., amorphous, quasicrystals, nanocrystalline) and compos- ite materials. In addition, it has been employed for reducing some metallic oxides by milling the oxide pow- ders with metallic reducing agents at room temperature. The MA is an unique process in that a solid state reac- tion takes place between the fresh powder surfaces of the reactant materials at room temperature. Consequently, it can be used to produce alloys and compounds which are difficult or impossible to be obtained by the conven- tional melting and casting techniques [1,2]. The most important advantage of this method with respect to other alloying methods is feasibility of addi- tion of alloying elements for improvement of mechanical and physical properties of alloys. Since mechanical alloying is a kind of high energy rate milling thus, all effective milling parameters can be affected on the process [3]. The used mills for mechanical alloying can be divided to three kinds: i.e., vertical, horizontal and vibration mills. Their difference can be attributed to the efficiency and alloying time [4]. 0261-3069/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2004.12.011 * Corresponding author. Tel./fax: +98 511 8829541. E-mail address: zebarjad@ferdowsi.um.ac.ir (S.M. Zebarjad). www.elsevier.com/locate/matdes Materials and Design 27 (2006) 684–688 Materials & Design