Effect of silicon carbide nanoparticles on hot deformation of ultrafine-grained aluminium nanocomposites prepared by hot powder extrusion process

Abstract

The flow behaviour of Al–SiC nanocomposites prepared by mechanical milling and hot powder extrusion methods was studied at different temperatures (350–500°C) and strain rates (0.005–0.5 s⁻¹). The flow of the Powder metallurgy nanocomposites exhibited a peak stress followed by a dynamic flow softening behaviour. It was shown that mechanical milling increased high-temperature strain rate sensitivity of ultrafine-grained (UFG) aluminium while decreasing its flow dependence to temperature. Constitutive analysis of the hot deformation process by Zener–Hollomon parameter (Z) also indicated a remarkable increase in the deformation activation energy (about 40%). Likewise, SiC nanoparticles (up to 2vol.-%) were shown to contribute in the high-temperature strengthening of UFG aluminium with a significant effect on its thermal stability. The findings were explained based on the pinning effect of hard nanoparticles on grain boundaries and mobile dislocations as well as microstructure stabilisation at elevated temperatures.

Keywords:

• Powder extrusion
• Aluminium nanocomposite
• Hot deformation
• Activation energy
• Constitutive analysis