籽晶取向对镍基高温合金定向凝固过程中杂晶的影响

Effect of Seed Crystal Orientation on the Stray Grain of Directional Solidified Ni-Based Superalloy

采用籽晶法,研究了不同角度的初始枝晶对高温合金DZ417G定向凝固组织影响。结果表明,在拉速为100μm/s的条件下,当初始枝晶的生长方向与轴向方向夹角较小时,获得生长方向一致的枝晶组织;当初始枝晶的生长方向与轴向方向夹角较大时,在枝晶尖端靠近坩埚臂的一侧有杂晶形成,并在截面变化后延续和促进了杂晶的生长。从枝晶臂的熔断和竞争生长角度对实验结果进行了分析。

Using seed crystal, influence of different dendrite orientations on the microstructures of the superalloy DZ417 G during directional solidification was investigated. The results indicated that the growth direction of dendrites did not change and no stray grain appeared at a small deviation angle from axis orientation. Nevertheless, with the increase of the deviation angle from axis orientation, the stray grains grew up. When section gets large, the stray crystal growth is promoted. Above phenomena were analyzed on the base of theories of the detachment of grain fragments from columnar dendritic fronts and competitive grain growth.