晶体生长方向对亚快速凝固结晶形貌的影响

采用区域熔化定向凝固装置，对冷却速度在１３～１３０Ｋ／ｓ范围内Ｎｉ－５％Ｃｕ合金的结晶形貌研究表明：在温度梯度ＧＬ３００Ｋ／ｃｍ条件下，晶体生长速度υ为５００μｍ／ｓ时，不同结晶取向的晶粒其结晶形貌不同。以＜１００＞方向生长的晶粒为树枝晶组织；以＜１２０＞方向生长的晶粒为细胞晶组织。当υ为８００μｍ／ｓ时，不同结晶取向的细胞晶间距不同。以＜１００＞方向生长的细胞晶间距是２８μｍ；以＜２１１＞方向生长的细胞晶间距是１６. ５μｍ。相同凝固条件下，同一晶粒内不同取向的分枝，结晶形貌不同。亚快速凝固条件下，树枝晶生长的生长方向已不完全按＜１００＞方向择优取向，细胞晶生长的择优取向性被抑制。

THE INFLUENCE OF THE CRYSTAL GROWTH ORIENTATION ON THE MICROSTRUCTURE IN HYPORAPID SOLIDIFICATION

The solidified microstructure of Ni-5wt% Cu alloy is researched at the cooling velocity range of 13～130K/s with zone melting unidirectional solidification apparatus. It indicates that the crystals with different crystal growth orientations have different solidified microstructures in the condition of G L=1 300K/cm,υ=500μm/s: the crystal with solidified orientation <100>is dendrite; the crystal with solidified orientation <120> is superfine cell. The crystals have different superfine cellular spacing due to the crystal growth orientation with G L=1 300K/cm, υ=800μm/s: superfine cellular spacing of the crystal with solidfied oriention <100> is 28μm, and that of the crystal with solidified oriention <21 1 > is 16. 5μm. In a grain, two parts have different microstructures due to the different orientations under the same solidification parameters. In hyporapid solidification, dendritic solidified orientation isn′t the preferential direction <100>; the preferential orientation is disposed in the superfine cellular growth process.