Microstructure refining of aluminum alloys using aluminothermic reaction with ZnO nanoparticles

• Using aluminothermic reaction, the grain refinement of aluminum alloy is achieved.
• Wetting and reduction reaction can be improved using semi-solid melt treatment.
• Mechanical properties of refined A356 alloy are improved.
• Refining mechanisms are analyzed in terms of nucleation site increment and grain growth restriction.

The wide popularities of grain refiner and modifier in aluminum alloy industry enable us to achieve improved properties and performances. Here, using aluminothermic reaction between nano-oxide particles (ZnO, ~20 nm in size) and aluminum alloy (A356), the microstructure refining effect on aluminum alloy is investigated. By the incorporation of nanoparticles with semi-solid melt treatment, the coarse primary aluminum dendritic microstructures are transformed to more fine and equiaxed structure showing improved mechanical properties. Converting mechanisms are interpreted in terms of the nucleation site increment, as well as the grain growth restriction, by decomposition and dissolution of the nano-oxide particles in aluminum alloy melt.