The grain structure evolution of the starter block and morphology of the isotherm under different conditions were simulated and experimented as well as the process of grain growth under the inclined isotherm.And the grain selection behavior in spiral block was investigated.The results reveal that the different heights of the starter block present different structural morphology.The starter block mainly optimizes the grain orientation by the competition between grains

and the preferential growth directions of the grains under different isotherms are different.The spiral block mainly selects the grain by the geometric constraint of the spiral channel on the dendrite growth

ensuring that only one grain entering the cavity and growing into a single crystal structure.