Effect of Zircon Particle Size on Age Hardening Behavior of A356 Alloy Based Composites

Melt stirring was used to introduce various amounts of zircon (ZrSiO4) particles of various sizes into aluminum alloy A356 of the Al – Si system. The effect of zircon particle sizes on age hardening behavior of stir-cast A356 alloy/zircon reinforced composites was studied by measuring microhardness after solution treatment and aging for various times. The structure of composites was studied by methods of optical microscopy, x-ray diffraction, scanning electron microscopy combined with energy dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy. The addition of zircon was found to accelerate age hardening of the matrix alloy. It is established that the maximum hardness increases and the time of attaining this maximum decreases with growing content of zircon particles and with reduction in their average size.