Microstructural and mechanical characterization of Al–Zn–Si nanocomposites

In this paper the addition of silicon nanoparticles into Al–Zn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the Al–Zn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material.