Effect of ZrO2 contents and ageing times on mechanical and electrical properties of Al–4.5 wt.% Cu nanocomposites prepared by mechanical alloying

Abstract

Al–4.5 wt.% Cu-based nanocomposites, reinforced with various weight percentages of ZrO2, have been synthesized via mechanical alloying method. The mixture powders were cold pressed and sintered at various firing temperatures up to 500 °C for 1 h in argon atmosphere. X-ray diffraction technique is utilized to investigate structural phases and elemental diffusion of milled powders. Transmission and scanning electron microscopies coupled with energy dispersive spectroscopy were employed to examine the morphology of milled powders and the microstructure of sintered specimens, respectively. Physical, mechanical and electrical properties of sintered samples were measured. Moreover, the sintered samples followed by heat treatments at 460 °C for 3 h, quenched and then, artificial aging was performed. The results revealed that Al2Cu precipitate phase was clearly observed after milling reflecting the formation of supersaturated solution of Cu in Al. Increase of ZrO2 contents caused weakness of Al2Cu phase, decrease in the crystal and particle sizes. Furthermore, successive increase of ZrO2 contents led to, in contrast to relative density and electrical conductivity, remarkable enhancement of mechanical properties of the nanocomposites. The results pointed out that microhardness, compressive strength and conductivity, for specific ZrO2 content, obviously increased at the early stage of aging and then, decreased.