SRR99镍基高温合金中晶界碳化物的微观组织研究

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	SRR99镍基高温合金中晶界碳化物的微观组织研究
	董晓鸣
学位类型	硕士
导师	杜奎 ; 杨志卿
	2012
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	材料物理与化学
关键词	镍基高温合金显微组织晶界碳化物 Nickel Based Superalloys Microstructure Grain Boundaries Carbides
摘要	"晶界区域的微观组织对镍基高温合金的持久性能具有十分重要的影响。本文利用扫描电子显微术、透射电子显微术以及相关的多种实验方法，系统地研究了SRR99型镍基高温合金热处理态双晶样品晶界区域的微观组织，以及晶界角度不同的双晶样品的持久性能和持久变形过程中晶界区域的微观组织演化。在双晶高温合金热处理态的微观组织中，随晶界角度的增加，晶界上尺寸小于0.5μm的M23C6颗粒的数量逐渐降低，大尺寸MC碳化物在晶界占据的长度逐渐增加，相应的双晶样品的持久性能逐渐下降。这种持久性能的差异，一方面受晶界本身的影响，另一方面归因于在不同角度的晶界上M23C6颗粒和MC碳化物分布的明显差异。在热处理态和持久变形过程中的微观组织中均发现了MC与M6C、M23C6的伴生结构，但是两种状态下，M6C和M23C6的形成机制不同。在热处理态组织中，MC周围局部的成分波动促进了其周围M6C和M23C6的形核；而持久实验过程中，载荷和高温条件促进了MC型碳化物分解形成M6C 和M23C6。MC碳化物在持久变形前期发生分解，并随变形的进展分解程度逐渐加剧。高温下的原子扩散影响了M23C6和晶界周围γ′相的形貌。M23C6逐渐由正方体生长为长方体，晶界周围的γ′相逐渐生长成沿晶界的γ′薄膜。实验中还发现了三种尚未被报道的MC与基体γ相的取向关系： [001]MC // [310]γ/γ′，(010)MC // (1-31)γ/γ′； [110]MC // [310]γ/γ′，(-11-1)MC // (001)γ/γ′； [001]MC // [001]γ/γ′，(-130)MC // (010)γ/γ′。在这些取向关系中，碳化物MC与基体γ相之间的相界面能较低，因此这些取向关系出现的频率较高。
其他摘要	"Microstructure of grain boundaries plays an important role on the stress rupture resistance of nickel based superalloys. In this dissertation, the microstructure of grain boundaries and the stress rupture property in heat treated SRR99 bicrystal nickel based superalloys were investigated by the means of scanning electron microscopy and transmission electron microscopy. Furthermore, the microstructure evolution of grain boundary during stress rupture tests was also studied. In the heat treated SRR99, the bicrystals with smaller misorientation angles contain denser M23C6 but fewer MC particles at the grain boundaries, and they present better property of stress rupture. The difference of stress rupture resistance is affected by the distribution of M23C6 and MC on the grain boundary with different misorientation angles. MC carbides decorated by discrete M6C and M23C6 particles were found both in the heat treated superalloy and the superalloy under stress creep. However, formation mechanisms of M6C and M23C6 were different for these two conditions. The formation of M6C and M23C6 particles in heat treated SRR99 is likely due to the local fluctuation of chemical composition around the vicinity of MC carbides, while under stress creep the tensile loading prompts MC decomposition, which produces M6C and M23C6 around the MC carbide. MC begins to decompose in the early stage of stress rupture test and intensify gradually with the stress rupture test. The atom diffusion in high temperature affects the morphology of M23C6 and γ′ at the grain boundary. M23C6 changed from cubic to rectangle and γ′ changed from cubic to thin film along the grain boundary. Novel orientation relationships (ORs) were observed between MC and matrix: [001]MC // [310]γ/γ′, (010)MC // (1-31)γ/γ′ ; [110]MC // [310]γ/γ′, (-11-1)MC // (001)γ/γ′ ; [001]MC // [001]γ/γ′, (-130)MC // (010)γ/γ′. These ORs correspond to low MC/matrix interfaces energy and therefore have high emergence frequency."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64516
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	董晓鸣. SRR99镍基高温合金中晶界碳化物的微观组织研究[D]. 北京. 中国科学院金属研究所,2012.