通过对NH_4Cl水溶液二维凝固过程的模拟实验,研究了柱状晶向等轴晶转变的条件及规律。结果表明,液相区内晶体形成后,在重力和液流作用下运动,其主要运动趋势是重力作用下的下落。不同凝固面接受下落晶体的能力不同,发生柱状晶向等轴晶转变的条件和机理不同,因而柱状晶区的长度也不同。文中提出了各凝固面柱状晶区长度的估算方法和利用“晶雨”促使柱状晶向等轴晶转变的措施。 Through the simulation experiment of two-dimensional solidification process of NH_4Cl aqueous solution, the conditions and regularities of the columnar to equiaxed crystal transformation were studied. The results show that after the crystals in the liquid zone form, they move under the action of gravity and liquid flow, and the main movement tendency is the drop under the gravity. Different coagulation plane to accept the ability to drop the different crystal, the occurrence of columnar to equiaxed crystal transformation of the conditions and mechanisms are different, and thus the length of the columnar crystalline region is also different. In this paper, the method of estimating the length of columnar zone in each solidification surface and the method of using “rain” to change the equiaxed grain of columnar crystal are proposed.