A new two region crystal micro physical model is established.It is used for the primary crystallization of hypoeutectic casts whose thickness is less than the critical value.

• 提出一种新的两区域结晶,这种两区域模型与三区域模型结晶模型的区别在于:在铸件的一次结晶过程中,铸件断面上不同时出现固相、固液相、液相三区共存的区域状态。