定向凝固组织的影响
(江苏大学 材料科学与工程学院，镇江 212013)
摘 要: 分别在750、850、950和1 050 ℃下，研究熔体过热处理对Al-4.7%Cu(质量分数)合金定向凝固组织的影响，利用综合热分析仪测定Al-4.7%Cu合金熔体结构特征及变化过程。结果表明：经过950 ℃和1 050 ℃过热处理的一次枝晶间距比在750 ℃常规过热直接定向凝固的分别减小了31.2%和36.2%；随着熔体过热时间的延长，一次枝晶间距减小，组织越来越细密；但随着低温保持时间的延长，一次枝晶间距增大，组织越来越粗大，表明熔体高温处理对定向凝固组织形态的影响逐渐衰退；熔体过热处理对Al-4.7%Cu合金定向凝固组织有显著影响的原因在于熔体过热处理改变了熔体结构状态。
关键字: 定向凝固；过热处理；一次枝晶间距；熔体结构；凝固组织
on directional solidification microstructure
of Al-4.7%Cu alloy
（School of Materials Science and Engineering, Jiangsu University,
Zhenjiang 212013, China）
Abstract:The influence of melt superheat treatment on the directional solidification microstructure of Al-4.7%Cu(mass fraction) alloy was studied at 750, 850, 950 and 1 050 ℃, respectively. The characteristics of the melt were measured by integrated thermal gravimetric analyzer. The results show that the primary dendrite arm spacing of the superheated samples at 950 and 1 050 ℃ decreases 31.2% and 36.2%, respectively, compared with the sample treated at 750 ℃. Along with the increase of melt superheat time, the primary dendrite arm spacing decreases and the microstructure is refined. However, if the melt stays at low temperature for a long time, the primary dendrite arm spacing increases and the microstructure coarsens, which indicates that the effect of melt superheat treatment on the morphology of directional solidification microstructure declines. The radical reason is that the superheat treatment makes the alloy microstructure changed.
Key words: directional solidification; superheat treatment; primary dendrite arm spacing; melt structure; solidification microstructure
