在温度梯度为200 K/cm和凝固速率为2-10 m/s下, Cu-1.0%Cr亚共晶合金的凝固组织中分别存在单相平界面和共晶、单相平界面和胞晶及胞间共晶、单相胞晶和共晶3种带状组织. 从实验和理论两方面阐明了上述带状组织的产生与合金定向凝固界面前沿的溶质分布有关; 形成的原因是合金未达到稳态凝固, 凝固速率和合金成分一直处于变化之中. 另外, 单相平界面和共晶的带状组织中, 合金凝固速率在单相平界面凝固中随着界面液相成分的增加而逐渐增大, 而在共晶组织中随着界面前沿液相成分的减少而逐渐减小.
Band-like microstructures were observed in directionally solidified Cu-1.0%Cr hypoeutectic alloy at the growth rate ranging from 2m/s to 10m/s and the temperature gradient of 200K/cm in liquid. There are three kinds of band-like microstructures, which are the planar interface plus coupled eutectic, the planar interface plus cellular structure with the growth of coupled eutectic, and cellular interface structure plus coupled eutectic, respectively. The formation mechanism of band-like microstructures has been illustrated by discussing the solute distribution ahead of solid-liquid interface in which the growth rate and alloy composition are changed at the non-steady state in directional solidification. In addition, the density difference between Cu phase and Cr phase is also an available factor to cause the formation of band-like microstructures in directionally solidified Cu-1.0%Cr hypoeutectic alloy.
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