【摘要】 研究了Zn 2 .75 %Cu合金在传统Bridgeman法和ACRT B法下定向凝固组织的差别。着重讨论了生长速度和液相强制对流对Zn Cu包晶定向凝固组织的影响。实验发现 ,在Bridgeman法定向凝固过程中 ,生长速度的增加使得液相中的温度梯度减小 ,一次枝晶间距减小 ,一次枝晶间距与生长速度和温度梯度的关系式为 :λ1=0 .6 0 6 4R-0 .2 5GL-0 .5。强制对流使得一次枝晶发生分叉和偏转。并且随着对流强度的加大 ,一次枝晶间距降低 ,二次枝晶的生长被抑制。包晶反应的存在 ,使得枝晶的尖端和二次枝晶熔解 ,造成了固相中枝晶和初生枝晶的差别更多还原

【Abstract】 The directional solidification of Zn 2.75Wt%Cu alloy by Bridgman and ACRT B (Accelerated Crucible Rotation Technology Bridgeman) methods have been experimentally investigated. Study concentrated on the influences of growth velocity and forced convection on the microstructure. The temperature distribution in the directional solidifying samples was measured to reveal the influences of growth velocity on the temperature gradient in front of the growth interface. The optical microstructure analysis reveals that primary dendrite spacing of the ε phase decreases with increasing growth velocity and temperature gradient, following the equation: λ 1=0.6064R -0.25 G L -0.5 . Forced convection during ACRT B process makes the primary dendrites branch off and twist. Meanwhile, the primary dendrite spacing is decreased and the secondary dendrite branches are restrained. The primary dendrites usually survive the following peritectic reaction, but the dendrites become sharper and the secondary dendrites may be dissolved.更多还原