Impact of coolant Water floW rate and temperature undersIde coolIng slope on solIdIfIcatIon WIth mIcrostructure and mechanIcal propertIes of casted aZ91 mg alloyPresent study describes about the effect of coolant water flow rate and coolant water temperature underside cooling slope on structural characteristics of casted aZ91 Mg alloy. here, over the cooling slope, hot melt flows from top to bottom. additionally, under the cooling slope, coolant water flows from bottom to top. Slurry gets obtained at bottom of cooling slope by pouring aZ91 Mg melt from top of the slope. Coolant water flow rate with coolant water temperature underside cooling slope warrant necessary solidification and shear to obtain aZ91 Mg slurry. Specifically, slurry at 5 different coolant water flow rates (4, 6, 8, 10, 12 lpm) and at 5 different coolant water temperatures (15, 20, 25, 30, 35°C) underside cooling slope are delivered inside metal mould. Modest coolant water flow rate of 8 lpm with coolant water temperature of 25°C (underside cooling slope) results fairly modest solidification that would enormously contribute towards enhanced structural characteristics. as, quite smaller/bigger coolant water flow rate/temperature underside cooling slope would reason shearing that causes inferior structural characteristics. ultimately, favoured microstructure was realized at 8 lpm coolant water flow rate and 25°C coolant water temperature underside cooling slope with grain size, shape factor, primary α-phase fraction and grain density of 63 µm, 0.71, 0.68 and 198, respectively. Correspondingly, superior mechanical properties was realized at 8 lpm coolant water flow rate and 25°C coolant water temperature underside cooling slope with tensile strength, elongation, yield strength and hardness of 250 MPa, 8%, 192 MPa and 80 hV, respectively.