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试样直径对Al-Cu合金定向凝固温度梯度和一次枝晶间距的影响 总被引:1,自引:0,他引:1
采用直径为4min和7min的试样对Al-4%Cu(质量分数,下同)合金进行定向凝固实验。研究表明:小直径试样温度梯度更高,但温度梯度变化幅度并未与试样直径比成线性比例。试样直径较小,胞/枝晶间距相应较小。获得直径为4min和7min试样一次枝晶间距与生长速率的关系,一次枝晶间距和生长速率、温度梯度的变化关系,且与理论值相符合;一次枝晶间距实验结果与TRIVEDI模型符合较好。 相似文献
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采用定向凝固技术研究A1-4%Cu(质量分数)合金凝固界而形态和胞/枝晶间距调整.结果表明,在ν=30um/s低速时,枝晶通过竞争淘汰调整一次枝品间距;在ν=300um/s高速时,枝晶通过尖端开裂而不是以往的三次枝生长调整间距.尖端半径与枝品间距相互影响,在稳定枝晶间距范围内随枝晶间距的增加而增大.采用LMK理论进行分析,得到枝晶尖端开裂是尖端溶质浓度变化引起尖端半径发生变化.通过扩散模型建立了枝晶问距与凝固界面成分之间的关系,得出枝晶通过自动调节间距大小来降低成分过冷作用. 相似文献
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The relationship between primary dendrite arm spacing and sample diameter was studied during directional solidification for Al-4%Cu (mass fraction) alloy. It is shown that primary dendrite spacing is decreased with the decrease of the sample diameter at given growth rate. By regressing the relationship between primary dendrite arm spacing and the growth rate, the primary dendrite arm spacing complies with 461.76v-0.53, 417.92v-0.28 and 415.83v-0.25 for the sample diameter of 1.8, 3.5 and 7.2 mm, respectively. The primary dendrite spacing, growth rate and thermal gradient for different sample diameters comply with 28.77v-0.35G-0.70, 23.17v-0.35G-0.70 and 23.84v-0.35G-0.70, respectively. They are all consistent with the theoretical model , and b1/a1=2. By analyzing the experimental results with classical models, it is shown that KURZ-FISHER model fits for the primary dendrite spacing in smaller sample diameters with weaker thermosolute convection. Whereas TRIVEDI model is suitable for describing primary dendrite arm spacing with a larger diameter (d>2 mm) where convection should be considered. 相似文献
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