Fracture behavior of  LM-13 aluminum alloy reinforced with different wt.% of nano-ZrO₂ particles, solidified under  various cryogenically cooled chills (at -80^oC), 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 nano chilled composites were developed exclusively for aero space applications.       

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%.  Cryo chills of thickness 25, 20, 15, 10 and 5 mm 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 and fracture toughness 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.  Finally heat capacity of the cryo-chill is identified as an important parameter which affects mechanical properties.    

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