The effect of waterjet beginning time on the microstructure and mechanical properties of A356 aluminum alloy during the ablation casting process

The effect of delay time (time interval between melt pouring and waterjet beginning) achieved by ablation process on the microstructure and mechanical properties of A356 aluminum alloy is investigated. By applying the process of ablation cooling 0.5 min after melt pouring, eutectic silicon and iron intermetallic size were reduced extremely and the dendrite arm spacing was refined almost considerably. For 0.5 min and 1 min of delay times ablated samples, besides interdendritic phases size reduction, the morphology of eutectic silicon was converted from coarse needle-like particles to fine and fibrous morphology. Also gas and shrinkage porosities were minimized considerably without any melt treatment. The mechanical properties of 0.5 min ablated samples were improved significantly and in comparison with the conventional casting samples in the sand mold, the ultimate tensile strength and elongation were increased from 161 MPa to 264.5 MPa and from 3% to 12% respectively. Fractography investigations showed a ductile fracture surface for ablated samples.