摘要
通过实时观察技术研究了NH4Cl等轴晶在过热NH4Cl-70%H2O溶液中的下落熔化过程。实际测定了不同尺寸枝晶碎片在过热溶液中的存留时间,并将其与基于纯扩散熔化模型计算的存留时间进行比较。结果发现,大量等轴晶下落时在其后侧形成枝晶碎片尾迹。实际存留时间与纯扩散条件下的存留时间的比值随着枝晶碎片尺寸的减小而增大。通过对纯铝枝晶碎片的存留时间进行估算,其金属枝晶碎片的熔化时间会在数十秒到百秒之间;如果枝晶碎片在熔尽之前进入了过冷生长区,则会被保留并成为后续凝固等轴晶的生长核心。
The falling melting process ofNI-hCl equiaxed dendrite in superheated transparent NH4CI-70wt%H,O solution was studied. The residence time of dendrite fragments in experiment was compared with the residence time calculated from a diffusion controlled kinetic equation. The results show that a large amount of dendrite fragments are detached from dendrite crystal during its falling in superheating solution. The ratio between the measured time and the calculated time increases with the decrease of the size of dendrite fragments. By calculating the residence time of pure aluminum dendrite fragments, it is found that residence time of metallic dendrite fragmentsis is between tens of seconds and hundreds of seconds. If dendrite fragments are retained, they can become the nucleation cores of equiaxed dendrite in the subsequent casting process.
出处
《铸造技术》
CAS
北大核心
2013年第6期716-719,共4页
Foundry Technology
基金
国家重点基础研究发展计划(2011CB610402)
国家自然科学基金(51271213
50901061)
凝固技术国家重点实验室(西北工业大学)自主经费(02-TZ-2008
36-TP-2009)资助课题
关键词
等轴晶
过热熔体
枝晶碎片
存留时间
equiaxed dendrite
superheated melt
dendrite fragment
residence time
