International Journal of Modern Physics B Vol. 27, No. 11 (2013) 1350036 (10 pages) c  World Scientific Publishing Company DOI: 10.1142/S0217979213500367 MILLING TIME — DEPENDENT MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NANOSTRUCTURED Al–Si ALLOY A. A. EBNALWALED * and M. ABOU ZIED Physics Department, Faculty of Science, South Valley University, Qena, 83523, Egypt * kh ebnalwaled@yahoo.com Received 3 November 2011 Revised 7 October 2012 Accepted 14 January 2013 Published 11 April 2013 Al–7% Si alloys were prepared by ball milling technique under different milling time. The effect of milling time on the microstructure and mechanical properties were studied. The results indicate that the grain size decrease with increasing the milling time, the average dislocation density, ρ, was found to exhibit a drastic increase by increasing the milling time, the median diameter, µ decreases, while the value of width parameter, σ is approximately constant with increasing the milling time. The value of Vickers hardness (HV) increases by increasing milling time, this increase was attributed to the refinement of grains with increasing milling time. Keywords : Ball milling; nanocrystalline; microstructure; microhardness and Al–Si alloys. 1. Introduction Al–Si alloys are widely used because of their low density, good castability and high strength at elevated temperatures. They suffer, however, from low ductility or toughness, which limits their use to applications. 1,2 Hypereutectic Al–Si alloys have been applied in automobile engine cylinders, cylinder heads, pistons, cylinder liners etc. 3–6 The brittleness of coarse Si crystals is the main reason responsible for the poor properties of Al–Si alloys because coarse Si crystals lead to prema- ture crack initiation and fracture in tension. Therefore, many efforts have been made in the microstructural modification of casting Al–Si alloys in order to achieve fine Si phases with beneficial shapes and distributions through, for instance, pro- moting heterogeneous nucleation and preventing growth of Si crystals by alloying additions. 7–9 There has been a continuous effort over the past years to enhance * Corresponding author. 1350036-1