镍基单晶高温合金蠕变过程中位错组态及芯部结构研究

发布时间：2018-05-04 22:37

本文选题：镍基单晶高温合金 + 蠕变　；参考：《山东大学》2017年博士论文

【摘要】：镍基单晶高温合金具有优异的蠕变性能和较好的组织稳定性,是发动机涡轮叶片的首选材料。本文设计六种Cr和Ru含量不同的镍基单晶高温合金,经1100℃和137MPa下蠕变试验,应变量1%截断后,借助扫描电子显微镜和透射电子显微镜研究合金的微观结构,着重研究Cr和Ru单独和交互作用下各合金的蠕变性能及影响机制,蠕变过程中位错的演变规律,高温合金γ相内错配位错、滑移位错、及扩展位错形貌及芯部结构,γ'相超位错形貌、超分位错的位错锁组态及扩展位错组态,蠕变过程中γ/γ'界面结构及界面位错网结构,进而总结镍基单晶高温合金蠕变过程中各类位错强化机制,是对高温合金位错理论系统的总结和深入完善。(1)Ru元素和Cr元素单独作用使合金内γ'相筏排化程度增强,γ/γ'界面处形成位错网,蠕变性能提高。Ru和Cr交互作用对合金蠕变寿命的影响分为中Cr和高Cr两种情况:中Cr(2.8wt.%)下添加Ru元素,合金蠕变寿命明显延长;高Cr(5.6wt.%)下添加Ru元素,合金内析出大量TCP脆性相,蠕变性能显著降低。本研究首次对"Ru元素的添加造成合金元素的逆分配行为,抑制TCP相的析出"这一传统结论提出不同意见并分析产生机制。对合金设计的指导意义为:合金中添加Ru元素时可适当降低Cr元素的含量或者寻找Cr和Ru的最佳含量比。(2)镍基单晶高温合金蠕变过程中位错的演变规律为:蠕变第一阶段初期位错被限制在γ相内滑移;蠕变第一阶段末期、稳态蠕变初期,位错在γ/γ'界面处发生位错反应形成位错网;蠕变第二阶段末期、第三阶段初期,位错成对切入γ'相,形成超位错。(3)γ相内错配位错通常位于γ/γ'界面,在错配应力作用下产生,芯部表现为呈"V"形分布的两个{111}半原子面,芯部原子畸变复杂,可以看作两刃型位错原子芯部畸变叠加的结果,位错强化依赖于a/2110型分位错间的反向畴界(APB)。滑移位错多为长位错线,60°混合型,位错段交滑移至{001}面后形成K-W锁达到强化效果,多分布于γ基体水平通道和水平通道与垂直通道的交界处。扩展位错短而直,通过插入一层{110}型半原子面或者{111}面的不完全滑移形成,a/6112型分位错间的复杂堆垛层错(CSF)能够使位错滑移限制在某一{111}面内达到强化效果。(4)γ'相位错(超分位错)成对存在形成超位错。超分位错分解为Frank不全位错和Shockley不全位错,Frank不全位错不可动,可以"锁住"整根位错,构成位错锁组态。超分位错分解为两个Shockley不全位错,CSF限制位错运动,构成扩展位错组态。Frank不全位错通过插入一层{111}半原子面形成,芯部压应力占主体,不关于半原子面所在平面对称。Shockley不全位错通过{111}面的不完全滑移形成。(5)蠕变过程中γ/γ'界面呈锯齿形,稳定性高,是位错运动和元素扩散共同作用的结果,能有效阻碍位错运动,是高温合金内位错强化的另一表现方式。γ/γ'界面位错以位错网形式存在,随蠕变过程进行,经四边形位错网、六边形位错网到类四边形位错网演变,由疏松到细密的演变,由不稳定向稳定的演变,位错由可动向不可动演变。位错网空间结构稳定性高,滑移位错不易通过。其中,alOO型界面超位错芯部以位错偶极子形式分解,通过滑移-攀移机制形成。
[Abstract]:Nickel based single crystal superalloy has excellent creep properties and good microstructure stability. It is the first choice for engine turbine blades. In this paper, six kinds of nickel based single crystal superalloys with different Cr and Ru content were designed. After the creep test at 1100 and 137MPa, the strain 1% was truncated with the aid of scanning electron microscope and transmission electron microscope. The microstructure of the alloy is focused on the study of the creep properties and influence mechanism of Cr and Ru, the evolution of dislocation, dislocation dislocation, slip dislocation, dislocation morphology and core structure, gamma 'Superdislocation profile, Superdislocation dislocation lock configuration and extended dislocation configuration, In the process of creep, gamma / gamma interface structure and interface dislocation network structure are used to summarize the mechanism of dislocation strengthening during the creep process of nickel base single crystal superalloy. It is a summary and thorough improvement of the theoretical system of Superalloy dislocation theory. (1) the effect of Ru and Cr elements alone on the enhancement of the rafting degree of the gamma 'phase raft in the alloy, and the formation of dislocation networks at the gamma / gamma interface The effect of the interaction of.Ru and Cr on the creep life of.Ru and Cr is divided into two kinds of conditions: medium and high Cr: adding Ru element to Cr (2.8wt.%), the creep life of the alloy is obviously prolonged; the addition of Ru element to the high Cr (5.6wt.%) is a large amount of TCP brittle phase precipitated in the alloy, and the creep property can be significantly reduced. This study is the first time for the addition of "Ru elements" The reverse distribution of alloy elements and inhibition of the precipitation of TCP phase "this traditional conclusion puts forward different opinions and analyses the mechanism. The guiding significance of the alloy design is that when adding Ru elements in the alloy, the content of Cr elements can be reduced or the optimum content ratio of Cr and Ru is found. (2) the dislocation evolution during the creep process of the nickel base single crystal superalloy. The law is that the dislocation of the first stage of creep is confined in the phase of the gamma phase, the first stage of creep, the initial stage of the steady creep, dislocation in the gamma / gamma interface and the dislocation network at the gamma / gamma interface, the second stage of creep, the early stage of the third stage, the dislocation into the gamma phase, and the formation of Superdislocation. (3) the mismatch dislocation in the gamma phase is usually located in the gamma / gamma boundary. Under the action of mismatched stress, the core is shown to be two {111} semi atomic planes with "V" shaped distribution, and the core atomic distortion is complex. It can be regarded as the result of the superposition of the core distortion of the two edged dislocation atom, and the dislocation strengthening depends on the reverse domain boundary (APB) between the a/2110 dislocations. The slip dislocation is mostly the long dislocation line, the 60 degree mixed type, the dislocation segment intersection. After sliding to the {001} surface, the K-W lock is formed to achieve the strengthening effect, which is mostly distributed at the junction of the horizontal and horizontal channels of the gamma matrix. The extended dislocation is short and straight, and is formed by inserting a layer of {110} type semi atomic surface or the incomplete slip of the {111} surface, and the complex stacking fault (CSF) can restrict the dislocation slip between the a/6112 type dislocations. The enhancement effect is achieved in a certain {111} plane. (4) the gamma phase error (superposition dislocation) is Superdislocation. The superposition dislocations are divided into Frank incomplete dislocations and Shockley dislocations, Frank incomplete dislocations are unmovable, and the whole dislocation can be locked up to form a dislocation lock configuration. The superposition dislocations are decomposed into two Shockley incomplete dislocations and CSF limited dislocations. Motion, forming an extended dislocation configuration.Frank incomplete dislocation by inserting a layer of {111} semi atomic plane, the core pressure stress is the main body, and the plane symmetric.Shockley incomplete dislocation of the semi atomic plane is formed by the incomplete slip of the {111} surface. (5) during the creep process, the gamma / gamma interface is serrated, the stability is high, and it is dislocation movement and element expansion. The result of the scattered interaction can effectively impede dislocation movement and be another expression of dislocation strengthening in the superalloy. The dislocation of the gamma / gamma interface exists in the form of dislocation network, which evolves with the quadrangular dislocation net, hexagonal dislocation net to the quadrangular dislocation network, and the evolution from the loose to the fine-grained, from the unstable to the stable. The dislocation network has high stability, and the slip dislocation is not easy to pass through the dislocation network. Among them, the Superdislocation core of the alOO interface is decomposed in the form of dislocation dipole, and is formed by sliding climbing mechanism.

【学位授予单位】：山东大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG132.3

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