Microstructural Refinement for the Reduction of Casting Thickness in Ni-Zr-(Al) Eutectic Composites and Evaluation of the Cooling Rates
Anushree Dutta, Dyutiman Barman, Utkarsh Sinha, Jayanta Das
28 Jan 2020
The variation of casting thickness and solute content may play a significant role to alter the microstructure, thus, mechanical, creep and other properties. Therefore, the present work aims on the microstructural modification in terms of the length scale of the constituent phases and microstructure homogeneity in differently cast rods (Ã˜=2 mm, 3mm, and 5 mm) and ingots of (Ni0.92Zr0.08)100-xAlx (0 â‰¤ x â‰¤ 4 at.%) composites, which are finally correlated with the cooling rates. The composites are comprised of Î³-Ni dendrites embedded on a eutectic matrix of Î³-Ni and Ni5Zr lamellar phases. The secondary dendritic arm spacing (SDAS) and average eutectic lamellae thickness (Î»w) are refined from 6.00Â±0.9Î¼mto 1.75Â±0.20 Î¼m, and from 275Â±6 nm to 40Â±3 nm respectively with the variation of casting thickness. The rods are solidified under very rapid cooling rate upto 1.6Ã—104K/s resulting very fine and homogeneous microstructure. The segregation effect is minimised in the smaller diameter rods resulting very uniform microstructure throughout the cast rods.