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使用立体显微镜及深孔光纤投影仪对模拟大型钢锭内部液相对流与宏观组织的Pb-5Sn和NH_4CL-H_2O铸锭的A型偏析进行了研究.观察到A型偏析的两种形成机制.研究发现:(1)形成A型偏析的基本条件是较低的凝固速度与一定的水平温度梯度;(2)A型偏析的形貌取决于凝固速度与一次枝晶阵的取向;(3)可通过控制凝固速度,温度梯度,一次枝晶阵取向及高径比防止A型偏析.
A-type segregation of Pb-5Sn and NH_4CL-H_2O ingots simulated by liquid-phase convection and macrostructure in a large ingot ingot was investigated by stereomicroscope and deep-hole fiber projector, and two formation mechanisms of segregation of type A were observed. The results show that: (1) The basic conditions for the formation of Type A segregation are lower solidification rate and certain horizontal temperature gradient; (2) The morphology of Type A segregation depends on the solidification rate and orientation of primary dendrites; (3) Type A segregation is prevented by controlling the solidification rate, temperature gradient, primary dendrite orientation and aspect ratio.