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测量不同直径管中Pb-26%Bi(质量分数)亚包晶合金定向凝固试样的初生α相的一次枝晶间距,考察熔体对流对初生α相一次枝晶间距的影响。结果表明:一次枝晶间距随着试样直径的增大而增大。在凝固速度5μm/s,直径1.8mm的试样中的初生α相的一次枝晶间距为161.5μm,而在直径为7mm的试样中则增大到240.4μm。大直径试样中的熔体强对流将促进有效溶质扩散,加快包晶反应和包晶转变导致细小的α枝晶溶解,从而使得初生α相的一次枝晶间距增大。
The primary dendritic spacing of the primary α phase of the Pb-26% Bi (sub-peritectic) sub-peritectic alloy in different diameters was measured and the influence of melt convection on the primary dendritic spacing was investigated. The results show that the primary dendrite spacing increases with the increase of specimen diameter. The primary dendritic pitch of the primary α phase in the sample having a solidification speed of 5 μm / s and a diameter of 1.8 mm was 161.5 μm, and increased to 240.4 μm in a sample having a diameter of 7 mm. The strong convection of the melt in the large diameter sample will promote the diffusion of effective solute, accelerate the peritectic reaction and peritectic transformation lead to the small α dendrite dissolution, so that the primary dendritic spacing increases.