重力对镍基单晶高温合金枝晶生长和微观偏析的影响  

Effect of Gravity on Dendrite Growth and Microsegregation of Ni-based Single Crystal Superalloy

作　　者：孔亚非 罗兴宏[1,2] 李洋 刘实[1,2] KONG Yafei;LUO Xinghong;LI Yang;LIU Shi(Shi-Changxu Innovation Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China)

机构地区：[1]中国科学院金属研究所师昌绪先进材料创新中心,沈阳110016 [2]中国科学技术大学材料科学与工程学院,沈阳110016

出　　处：《材料研究学报》2023年第10期770-780,共11页Chinese Journal of Materials Research

基　　金：中国载人航天工程空间应用系统项目。

摘　　要：使用长50 m的落管研究Ni-Cr-Al-W-Ta镍基单晶高温合金在重力(1g)和微重力(μg)条件下的凝固行为。用金相显微镜(OM)观察合金的凝固组织并用图像分析软件测量和统计一次和二次枝晶间距,使用扫描电镜能谱(SEM-EDS)测定不同位置枝晶干与枝晶间的化学成分并计算微观偏析系数。结果表明,在重力和微重力条件下这种合金的枝晶特征和合金元素的微观偏析明显不同。重力样品一次和二次枝晶间距比微重力样品的大,随着凝固距离的增大一次枝晶间距的差异变大,而二次枝晶间距的差距变化不大。随着凝固的进行,微重力样品枝晶间Ta、Cr和Al元素的含量呈现先明显升高后略微降低的趋势,W元素含量呈现逐渐下降的趋势,枝晶间液相的密度呈现略微降低的趋势。重力样品枝晶间Ta、Cr和Al元素含量的分布趋势与微重力样品基本相似,W元素含量的分布则与微重力样品明显不同,大部分凝固阶段呈上升趋势,使枝晶间液相的密度沿逆重力方向提高。上述结果表明,在重力条件下凝固前沿溶质密度差导致的对流作用微弱,不是造成枝晶间距增加的主要原因,主要原因应该与凝固前沿热对流造成的温度梯度的降低有关。The solidification behavior of a Ni-based Ni-Cr-Al-W-Ta single crystal superalloy in normal gravity(1g)and microgravity(μg)conditions were comparatively investigated by using a 50 metre-high drop tube.The solidification microstructure of the alloy was observed using optical metalloscopy(OM),and the primary and secondary dendrite spacing of the samples were measured and counted by using an image analysis software.Scanning electron microscope(SEM-EDS)was used to determine the chemical compositions of dendrite trunk and interdendrite at different locations,and then the microsegregation coefficient was calculated.The results show that the dendrite characteristics and microsegregation are significantly different in 1g andμg conditions respectively.The primary and secondary dendrite spacing tested in 1g sample are larger than those inμg sample,and the difference of primary dendrite spacing between 1g andμg sample gradually increases with the increase of solidification distance,while the difference of secondary dendrite spacing does not change much.With the process of solidification,the contents of Ta,Cr and Al between dendrites tested inμg sample show a trend of increasing obviously at first and then decreasing slightly,while the W content has a trend of decreasing gradually,and the interdendritic liquid phase density shows a trend of decreasing slightly.The distribution of the Ta,Cr and Al content between dendrites tested in 1g sample are basically similar to those inμg sample,while the distribution of W is significantly different,showing an upward trend in most solidification stages,resulting in the increase of the interdendritic liquid phase density just along the opposite direction of gravity.These results indicate that the convection effect caused by the solute density difference at the front of solidification interface was weak in normal gravity condition,which was not the main reason for the increase of dendrite spacing.It is believed that the main reason should be related to the reduction of temperature g

关 键 词：金属材料 镍基单晶高温合金 枝晶生长 微观偏析 微重力 凝固 

分 类 号：TG132.32[一般工业技术—材料科学与工程]