Effect of the nozzle diameter and melt velocity at the tundish outlet on solidification along microstructural and mechanical properties of the cooling slope casted AZ91 Mg alloy

Experiments were carried out for investigating the effect of the nozzle diameter and melt velocity on solidification along microstructural and mechanical properties of the cooling slope casted AZ91 Mg alloy. Investigations involved five different nozzle diameters (4, 6, 8, 10, and 12 mm) with five different melt velocities (0.1, 0.2, 0.3, 0.4, and 0.5 m/s). Finally, a moderate nozzle diameter of 8 mm with a melt velocity of 0.3 m/s rendered reasonably moderate solidification. Additionally, the favoured microstructure was observed with particle size, a shape factor, α-phase fraction and particle densities of 62 μm, 0.75, 0.80 and 195. Correspondingly, better mechanical properties were observed with tensile strength, ductility, yield strength and hardness of 265 MPa, 7.5%, 200 MPa and 80 HV, respectively. The nozzle diameter/melt velocity produces poorer castings. Furthermore, the retaining/escaping of alloy elements along gases occurs throughout processing; in this case, the escape of alloy elements lessens strength whereas the escape of gases boosts strength. Moderate control of casting parameters rendered superior properties.