中文摘要：

研究了定向凝固工艺对高温合金DZ417G模拟叶片变截面疏松形成的影响。结果表明,模拟叶片靠近中心圆柱一侧变截面疏松含量比靠近炉壁一侧高1个数量级。在一定浇注温度范围内（1480-1580℃）,随浇注温度的升高,靠近中心圆柱变截面位置疏松含量先升高后降低,在浇注温度为1550℃时疏松含量最高;而靠近炉壁侧变截面疏松含量随浇注温度升高略有降低。在一定抽拉速度范围内（1-10 mm/min）,随着抽拉速度的升高,靠近中心圆柱变截面位置疏松含量逐渐升高,而靠近炉壁位置疏松含量逐渐降低。根据以上结果,针对模拟叶片变截面位置提出了浇注温度、抽拉速度和显微疏松含量的对应关系。此外,定向凝固工艺对变截面疏松形成的影响主要是由固液界面前沿的温度梯度变化造成的。

英文摘要：

The influence of directionally solidified process on porosity in cross-section transitions of dummy blade nickel-based superalloy DZ417G was investigated. It is found that the content of porosity at transition platform near the central runner is an order of magnitude higher than that near the heater. In a certain casting temperature range（1480-1580 ℃）, with the increase of casting temperature, the content of porosity at transition platform near the central runner increases at first and then decreases, and the temperature with maximum content of porosity is 1550 ℃; however, in this casting temperature range, with the increase of casting temperature, the content of porosity at transition platform near the heater decreases a little bit. In a certain withdrawal velocity range（1-10 mm/min）, with the increase of withdrawal velocity, porosity at transition platform near the central runner increases gradually; however the porosity at the opposite side part decreases. Based on these results, the relationship between casting temperature, withdrawal velocity and the content of porosity in transition platform dummy blade has been proposed. Besides, the influence of directional solidification process on the formation of porosity on the cross-section of the platform is mainly caused by the variation of temperature gradient of the solid-liquid interface.