摘要
采用籽晶法控制晶体取向,研究了不同抽拉速率下镍基高温合金汇聚型双晶的竞争生长.结果表明,低抽拉速率下,非择优枝晶能够穿插进入择优枝晶间的液相通道,抑制择优枝晶的生长,使晶界向择优晶粒方向偏移.高抽拉速率下,非择优枝晶几乎全部被晶界择优枝晶阻挡,晶界与择优枝晶干平行.非择优枝晶进入择优枝晶间的液相通道使择优枝晶萎缩消失是非择优晶粒淘汰择优晶粒的主要因素,并以此提出了抽拉速率对竞争生长的影响机制.
Ni-based single crystal superalloy has been widely used in turbine blades due to its excellent high temperature mechanical behavior. In order to completely exhibit high temperature mechanical properties, the seed method has been used to produce Ni-based single crystal components for [001] orientation paralleling to main force direction. Stray crystals, which unexpectedly nucleate in the melt-back region, will competitively grow with seed during directional solidification. It is important to profoundly understand the mechanism of competitive growth to find ways of overgrowing stray crystal during producing Ni-based single crystal components. However, within the published research there are conflicting views on the mechanism of competitive growth at converging case. Bi-crystal converging competitive growth was investigated in Ni-based single crystal superalloy with differ- ent pulling rates using seed technology. A series of polishing and imaging quenching interface were done for the po- sitional relationship of dendrites near grain boundary in 3D reference. It was found that solidification microstruc-tures were different with different crystal orientations. Unfavorable oriented dendrite tilting to heat flux restrained favorable oriented dendrite aligning to heat flux mainly thought inserting into the favorable oriented dendrites chan- nel, and this resulted in unfavorable oriented dendrite overgrowing favorable oriented dendrite at low pulling rate. However, at high pulling rate the unfavorable oriented dendrites mainly blocked by grain boundary favorable ori- ented dendrite and the grain boundary grew paralleling to favorable oriented dendrite core. Favorable oriented den- drite being depressed and vanished, owning to that unfavorable oriented dendrite inserting into favorable oriented dendrites channel result in adjusting primary dendrite spacing, is the main factor to favorable oriented grain over- grew by unfavorable oriented grain. According to above mechanism, effect of pulling rate on competitive growth at
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第8期897-904,共8页
Acta Metallurgica Sinica
基金
国家自然科学基金项目51331005
51171151和51501151
国家高技术研究发展计划项目2012AA03A511
国家重点基础研究发展计划项目2011CB610406
陕西省自然科学基金项目2014JM6227
西北工业大学基础研究基金项目3102014JCQ01022
先进航空发动机协同创新中心项目资助~~
关键词
镍基高温合金
竞争生长
抽拉速率
Ni-based superalloy, competitive growth, pulling rate
