Fracture behavior of cryogenically solidified aluminum-alloy reinforced with Nano-ZrO2 metal matrix composites (CNMMCs)

Abstract

Fracture behavior of LM-13 aluminum alloy reinforced with different wt.% of Nano-ZrO2particles, solidified under various shallow cryogenically cooled chills (at -80°C), cast using DMD (disintegrated melt deposition) technique followed by hot extrusion were investigated. The size of the particles dispersed varies from 50 to 80 nm and amount of addition varies from 3 to 15 wt.% in steps of 3 wt.%. Microstructural studies of the Nano-composite developed indicate that there is uniform distribution of the reinforcement in the matrix and mechanical properties reveal that presence of Nano- ZrO2 particles as dispersoid (up to 12 wt.%) and chill thickness (25 mm) has improved significantly the strength, hardness and fracture toughness with slight reduction in ductility. Fractography of the specimens showed that the fracture behavior of matrix alloy has changed from ductile intergranular mode to cleavage mode of fracture. Finally heat capacity of the shallow cryo-chill is identified as an important parameter which affects mechanical properties. Key words: Composites, mechanical, fracture, Nano, chill, shallow cryogenic, microstructure.