THE EFFECT OF HEAT TREATMENT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A356/ZrO2 NANO REINFORCED COMPOSITES

Abstract

Aluminum A356 alloys have several interesting properties to be used in automobile and aircraft industries. Recent studies have shown that the properties of cast aluminum alloys are modified by the insertion of reinforcement nanoparticles. This study investigates the microstructure and mechanical properties of ZrO 2 nanoreinforced A356 alloy in T6 heat treated condition. Some samples of as cast monolithic A356 and 3% ZrO 2 nanoparticles (30nm) reinforced A356 were prepared by stir casting from the semi-solid state followed by T6 heat treatment process. The samples were solution treated at temperature of 550°C for 2hours followed by aging at different temperatures (170°C&180°C), for different aging time (2hr,4hr&6hr). The results obtained in this work showed enhancement in the mechanical properties (ultimate strength, ductility and hardness). The as cast samples showed values of 119 MPa,4.5% &23 HRB, respectively, while the 3%ZrO 2 reinforced samples showed the values of 165MPa,4.7% &60 HRB, respectively. After T6 heat treatment, the same values changed to 198MPa, 6.4% &70HRB, respectively for the nanoreinforced samples. The microstructure morphology was changed from lamellar eutectic structure to spheriodized eutectic structure.