Amorphous alloys are promising materials for various applications because of their excellent properties, such as high strength and hardness, good corrosion resistance and superlative electrical and magnetic properties. Among various amorphous alloys, Cu-Zr-Al alloy system is one of the most important alloys because of suitable cost with high strength, high glass forming ability and low melting temperature. However, Cu-Zr-Al amorphous alloys show little room temperature plasticity and low toughness. To optimize room temperature fracture toughness, a microstructure consisting of crystalline phases dispersed in the metallic glass matrix was developed. The aim of this research was to synthesize Cu-Zr-Al/Al 2 O 3 nanocomposites using mechanical alloying (MA). Cu 60 Zr 40 powder mixture was first MA’d in order to synthesize Cu 60 Zr 40 amorphous alloy. Also, for the studying of milling energy on amorphization reaction, the Cu, Zr and Al powders mixture was MA’d in different mills, low-energy planetary mill, Spex mill and high-energy planetary mill. Evaluation of milled powders by X-ray diffractometry (XRD) shows that mechanical alloying in different machines did not lead to amorphization reaction even after long milling time. Thermodynamic investigation on the basis of extended Miedema’s model in ternary Cu-Zr-Al system illustrated that there is a thermodynamic driving force for formation of amorphous phase in this system, which is in contrast with experimental results. This discrepancy was attributed to the presence of high amount of impurities including oxygen and nitrogen in Zr powder that prevents amorphization reaction. Mechanical alloying of Cu 60 Zr 40 and Cu 50 Zr 43 Al 7 were repeated using higher purity Zr leading to the formation of amorphous structure with ZrO 2 phase after 40 h milling. In addition Cu 60 Zr 40 and Cu 50 Zr 43 Al 7 were prepared by induction melting and then milled for 10 h. The results showed that a fully amorphous Cu 60 Zr 40 and Cu 50 Zr 43 Al 7 alloys are obtained. Also, milling of Cu 60 Zr 40 prepared by induction melting with Cu, Al and CuO powders mixture led to formation of Cu 62 Zr 32 Al 4 /10%V Al 2 O 3 nanocomposite with Al 2 O 3 particles size of about 25nm. The hardness and elastic modulus of this nanocomposite were about 837 Vickers and 95GPa. Keywords Cu 50 Zr 43 Al 7 alloy, Amorphous materials, Mechanical alloying, Nanocomposite.
