Fig. 1 Thermal field distribution in α-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection: a $t = 1000\Delta t$, b $t = 1500\Delta t$, c $t = 2000\Delta t$, d $t = 2500\Delta t$, e $t = 3000\Delta t$, f $t = 3500\Delta t$, g $t = 4000\Delta t$, h $t = 4500\Delta t$, i $t = 5000\Delta t$

Fig. 2 Solute field distribution in α-Mg dendrite growth of Mg-5wt%Zn alloy with forced convection: a $t = 1000\Delta t$, b $t = 1500\Delta t$, c $t = 2000\Delta t$, d $t = 2500\Delta t$, e $t = 3000\Delta t$, f $t = 3500\Delta t$, g $t = 4000\Delta t$, h $t = 4500\Delta t$, i $t = 5000\Delta t$

Fig. 3 Thermal field distribution a $t = 2000\Delta t$, b $t = 4500\Delta t$, c $t = 7000\Delta t$ and solute field distribution d $t = 2000\Delta t$, e $t = 4500\Delta t$, f $t = 7000\Delta t$ in α-Mg dendrite growth of Mg-5wt%Zn alloy on $\left\{ {0001} \right\}$ crystal plane with forced convection

Fig. 4 Comparison of the thermal and solute distribution along the central axis (white dotted line) of α-Mg dendrite growth on {0001} crystal plane with and without forced convection: a, d $t = 2000\Delta t$, b, e $t = 4500\Delta t$, c, f $t = 7000\Delta t$

Fig. 5 Comparison of the thermal and solute distribution along the upstream dendrite tips perpendicular line (white dotted line) of α-Mg dendrite growth on {0001} crystal plane with and without forced convection: a, d $t = 2000\Delta t$, b, e $t = 4500\Delta t$, c, f $t = 7000\Delta t$

Fig. 6 Comparison of the thermal and solute distribution along the downstream dendrite tips perpendicular line (white dotted line) of α-Mg dendrite growth on {0001} crystal plane with and without forced convection: a, d $t = 2000\Delta t$, b, e $t = 4500\Delta t$, c, f $t = 7000\Delta t$

Fig. 7 Comparison of the dendrite tip temperature a and dendrite tip concentration b of α-Mg dendrite growth on {0001} crystal plane with and without forced convection

Fig. 8 Thermal field distribution a–e $t = 9000\Delta t$ and solute field distribution f–j $t = 9000\Delta t$ in α-Mg dendrite growth of Mg-5wt%Zn alloy on $\left\{ {0001} \right\}$ crystal plane with different flow velocities. The flow velocities from left to right are $v_{x} = 0.00$, $v_{x} = 0.20$, $v_{x} = 0.40$, $v_{x} = 0.60$, and $v_{x} = 0.80$, respectively

Fig. 9 Change in upstream dendrite tip velocities a and tip radius c, and downstream dendrite tip velocities b and tip radius d in α-Mg dendrite growth of Mg-5wt%Zn alloy on $\left\{ {0001} \right\}$ crystal plane with different flow velocities

Fig. 10 Comparison between the simulation and experimental results: a morphology of α-Mg dendrite of Mg-5wt%Zn alloy with forced convection at $t = 25000\Delta t$, b optical micrographs of as-cast Mg-5wt%Zn alloy on the longitudinal section under air cooling