<正> 控制柱状晶生长方向,实现任意方向的定向凝固,这对提高铸件性能具有重要意义。本文用类金属透明有机合金莰烯—1.2％环己醇,在定向凝固条件下,连续改变热流方向,在显微镜下直接观察结晶过程以探索控制柱状晶生长方向的可能性和途径。 实验结果表明,当温度梯度G和生长速率R的比值G/R>8×10~(50)C·s/cm~2时,固液界面为稳定的平面状。当G/R=5×10~(50)C·s/cm~2时,固液界面开始由平面状转向胞状形态。在界面不断旋转的过程中,平面状形态几乎不发生变化,临界胞状形态只有微小的变化,说明在这些界面形态中,晶体位向的影响很小。
Camphene-1.2% cyclohexanol which freezes like metals, has been used for the investigation of crystal growth during directional solidification with continuously changing heat flow direction. The interface morphology of the columnar crystal changed according to the heat flow and this led to a change in the growth direetion of the columnar crystals. For cellular growth, the cells lay between <001> and the heat flow direction, and approached more closely to the <001> as the ratio of temperature gradient to growth rate decreased. For dendritic growth, the trunks grew in the <001> direction and did not change whatever the direction of heat flow. In contrast the sidebranches were very much affected by the heat flow direction——the sidebranches on the side against heat flow direction developed faster. The direction of columnar crystals tended to follow the heat flow direction, but different mechanism operated depending on the interface morphology.
参考文献
| [1] | 黄卫东,西北工业大学铸造专业硕士论文,1984．屯屯屯屯屯屯{ |
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