摘要
采用浇注后进行电磁搅拌和在模壳内表面涂孕育剂铝酸钴相结合的方法,得到了晶粒组织细化至95μm、断面等轴晶比例达到99%以上的K417高温合金全铸件。使用电子探针、扫描电镜和光学显微镜研究了晶粒细化对枝晶组织、元素枝晶偏析、析出相和缩松的影响。结果表明:晶粒细化后,晶粒形态由粗大的树枝晶向粒状晶转变。其原因为电磁场和表面孕育剂作用下熔体中结晶核心的增殖和枝晶生长的抑制,其中,增殖结晶核心主要来源于电磁搅拌作用下初生枝晶的动力折断与熔断;电磁搅拌和表面孕育剂相结合实现的晶粒细化可以大幅减轻铸件中的枝晶偏析和缩松,并使γ′相、MC型碳化物和(γ+γ′)共晶的形态和分布得到明显改善。
The average equal-axed grain size of K417 superalloy casting could be refined to 95 μm and the proportion of equi-axed grains in a cross-section could be increased to 99% by imposing reversible electromagnetic stirring after pouring melt to the shell with surface nucleator CoAl2O4. The effects of grain refinement on the dendrite structures, precipitates, element segregation and shrink holes of cast superalloy K417 have been studied with EPMA, SEM and optical microscope. The results show that the grain morphology has transformed from dendrite to granulation after grain refinement since the crystal nucleation is increased and the growth is suppressed by electromagnetic field and surface nucleator. There into, the crystal nucleus increase due to the primary dendrite broken by the electromagnetic stirring. Furthermore, the micro-segregation and shrink holes are decreased greatly in the casts, and the morphology and distribution of γ′ phase, carbide and （γ＋γ′）eutectic can be greatly improved by the grain refinement.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2008年第5期784-788,共5页
Rare Metal Materials and Engineering
基金
国家自然科学基金资助项目(50474055)
关键词
高温合金
晶粒细化
枝晶组织
枝晶偏析
析出相
缩松
superalloy
grain refinement
dendrite structure
segregation
precipitate
shrink hole
