两种定向柱晶高温合金微观组织和蠕变机制的研究

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	两种定向柱晶高温合金微观组织和蠕变机制的研究
	王栋
学位类型	博士
导师	孙晓峰 ; 张健
	2010
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	定向柱晶高温合金晶界碳化物硼化物蠕变
摘要	"Re略微增加了合金中的共晶百分含量，改变了合金元素的偏析，减小了合金中铸态γ′相的尺寸；Re还促进共晶外围和晶界上μ相的析出。合金热处理后，Re明显细化了合金中的γ′相，促进了MC碳化物周围和晶界上μ相的析出。0Re合金中B元素明显偏聚于晶界，而2Re合金中B元素分布相对比较均匀。在975oC/255MPa蠕变变形过程中，两种合金晶内均析出了稳定的纳米M23C6碳化物。0Re合金蠕变第一阶段，晶界上分布着连续的纳米M5B3硼化物颗粒；在蠕变第二阶段，晶界主要由不连续的块状M23(C,B)6硼碳化物组成；在蠕变第三阶段，晶界上除了块状的M23(C,B)6硼碳化物外，又出现了连续的M5B3硼化物颗粒。2Re合金中存在的大量块状μ相并没有恶化合金的持久性能，γ′包层避免了晶界和碳化物周围裂纹的形成。在760oC/850MPa蠕变第一阶段，0Re和2Re合金最明显的特征是g¢相内存在两种不同方向的内禀或外禀堆垛层错，这些不同方向的层错发生交割，形成了层错锁。在蠕变第二阶段，0Re和2Re合金g¢相内出现了少量反相畴界，2Re合金还出现了少量微孪晶。在蠕变第三阶段，0Re合金堆垛层错明显减少，反相畴界明显增多，出现了贯穿γ、γ'相的平面堆垛层错；2Re合金堆垛层错没有明显减少，微孪晶明显增多。"
其他摘要	"Re increases slightly the volume fraction of g/g¢ eutectic and changes segregation behavior of alloying elements. Re decreases the size of g¢ phase. It also accelerates the precipitation of μ phase in the periphery of eutectic and at grain boundary. After heat treatment, Re refines the γ' and accelerates the precipitation of μ phase in the vicinity of primary MC carbide and at grain boundary. Enrichment of boron along the grain boundary is observed in 0Re alloy. On the contrary, relatively uniform distribution of boron is found in 2Re alloy. The precipitation of stable nano-scaled M23C6 carbide at intragranular region is observed during 975oC/255MPa creep in both alloys. For 0Re alloy, continuous film-like precipitates composed of many closely contacted nanosize-M5B3 boride are observed along the grain boundary at primary creep stage. Phases precipitated at grain boundary are mainly discrete blocky M23(C,B)6 boro-carbide during steady-state creep stage. Besides M23(C,B)6 boro-carbide, a continuous film-like M5B3 boride particles are again observed along grain boundary at tertiary creep stage. For 2Re alloy, the creep-rupture properties of the alloy are not affected by the presence of a large amount of blocky μ phase. It is found that the thick γ'-film plays a pivotal role in toughening the grain boundary and the interface between the μ phase (or carbides) and the matrix, preventing the formation of crack. At the primary creep stage at 760oC/850MPa, the most striking characteristic is that two intrinsic or extrinsic stacking faults with different direction are found in the γ' phase in 0Re and 2Re alloy. And the stacking fault locks are formed by reaction of these faults. At steady-state creep stage, antiphase boundary is found in the γ' phase. Few microtwins are also found in 2Re alloy. For 0Re alloy, at tertiary creep stage, stacking faults apparently reduce, with the significant increase of antiphase boundary. The extended stacking faults involving γ and γ ′ phases are also found. For 2Re alloy, there is no significant reduction for stacking faults. However, microtwins increase obviously."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64197
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	王栋. 两种定向柱晶高温合金微观组织和蠕变机制的研究[D]. 北京. 中国科学院金属研究所,2010.