Development and Mechanical Behavior of Cryogenically Solidified Aluminum-Alloy (LM-13) Reinforced with Nano-ZrO2 Metal Matrix Composites (CNMMCs) for Medical Applications

Abstract

Mechanical behavior of LM-13 aluminum alloy reinforced with different wt.% of nano-ZrO2 particles, solidified under various cryogenically cooled chills (at -80oC), cast using DMD (Dis-integrated Melt Deposition) technique followed by hot extrusion were investigated. The use of nano particles and cryogenic chilling enabled in strengthening mechanical properties of the composite. These composites were developed exclusively for applications in medical field.

The size of the particles dispersed varies from 50-80 nm and amount of addition varies from 3 to 15 wt.% in steps of 3 wt.%. Copper cryo end chills of thickness 25, 20, 15, 10 and 5 mm in which arrangements made to circulate liquid nitrogen were used to study the heat capacity of the chill on mechanical behavior of the composite developed. Microstructural studies of the nano-composite developed indicate that there is uniform distribution of the reinforcement in the matrix alloy with significant grain refinement and retention of residual porosity. 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, corrosion resistance and fracture toughness with slight reduction in ductility as compared against the matrix alloy but the composite developed can be rolled to very thin sections . Fractography of the specimens showed that the fracture behavior of matrix alloy has changed from ductile intergranular mode to mixed mode of fracture. Finally heat capacity of the cryo-chill is identified as an important parameter which affects mechanical properties.

Considering the above improvement in mechanical properties and corrosion resistance, the nano composite developed can be used in medical applications.

Key Words: Nano, Composite, Al-alloy, Cryogenic, Mechanical.