摘要
通过对传统定向凝固(HRS)及液态金属冷却(LMC)2种工艺制备的镍基单晶高温合金铸态微孔和固溶微孔尺寸与分布的定量表征,分析了制备工艺以及合金成分对单晶合金铸态及固溶微孔形成的影响.结果表明:合金成分的差异导致本研究中HRS合金铸态微孔体积分数低于LMC合金.2种合金经固溶热处理后,在靠近表面的贫Al层及附近均形成大量的圆形固溶微孔,该类微孔的数量随着与表面的远离而减少.高温空气环境下Al向表面扩散形成贫Al层,进而由于Kirkendall效应形成近表面固溶微孔.高温下枝晶干和枝晶间的元素在扩散过程中产生的Kirkendall效应是合金内部固溶微孔的主要成因.LMC合金较小的一次枝晶臂间距和较低的元素凝固偏析程度使得其内部产生的固溶微孔数量远小于HRS合金.
Effects of processing techniques and alloying chemistry on the formation of solidifica- tion and homogenization micropores were investigated in this study for two single crystal nickel-based superalloys with different compositions produced by Bridgman （HRS） and LMC processes. The resultsshow that the volume fraction of micropores in as-cast HRS alloy is lower than that in as-cast LM（J alloy, and they are mainly influenced by alloy chemistry. After solution heat treatment, external and internal homogenization micropores are observed to form at the Al-depletion zone near the surface region and the internal zone away from the surface, respectively. The number of external homoge- nization micropores reduces with increasing the distance away from the surface. Responding to high temperature oxidizing environment （in air）, the formation of such homogenization micropores is as- cribed to fast outward diffusion of A1, which lead to the formation of Kirkendall voids within the Al-depletion zone. Additionally, the formation of internal homogenization micropores at high temper- ature is due to Kirkendall effect during the diffusion process of alloying elements between dendrite and interdendrite regions. Smaller primary dendrite arm spacing and lower level of solidification segrega- tion in the LMC alloy results in much less internal homogenization micropores in comparison with the HRS alloy.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第10期1237-1247,共11页
Acta Metallurgica Sinica
基金
国家重点基础研究发展计划资助项目2010CB631201~~
关键词
单晶高温合金
微孔
固溶处理
定向凝固
液态金属冷却
single crystal superalloy, micropore, solution treatment, directional solidification,liquid metal cooling
作者简介
石倩颖，女，1986年生，博士生
