J. Hemanth, University, TUMKUR, India
In the present research nano- ZrO2 particulates were dispersed in aluminum alloy (LM 13) by chilled melt deposition technique followed by hot extrusion. 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%. 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 particulates and chilling has improved significantly the strength and hardness with slight reduction in ductility as compared against the matrix alloy. Fractography of the specimens showed that the fracture behavior of matrix alloy has changed from ductile intergranular mode to cleavage mode of fracture. Results of the thermal and electrical tests on the composites developed indicate that, thermal conductivity and electrical resistance both decreased with increase in reinforcement content. Figs. 1 and 2 shows microstructure of extruded and fractured CNMMC containing 12 wt% reinforcement.
Fig.1 Optical microstructure of extruded Fig.2 SEM Fractograph of NMMC (12 wt%
NMMC containing 12 wt.% reinforcement. ZrO2,) (Magnification 100 μm, 500 X) (500 X Magnification)
Summary: This particular chilled nano composite developed exclusively for aerospace applications. This composite has proved to be very light in weight with enhanced mechanical properties. This composite was developed in association with the defense research organization.
