二代镍基单晶高温合金的显徽结构演变
发布时间：2018-07-23 19:26
【摘要】：镍基单晶高温合金是广泛应用于航空发动机涡轮叶片的首选结构材料,其工作特点是高温和高应力环境。该类合金在高温下仍能保持优异的力学性能依赖于其特殊显微结构。镍基单晶高温合金显微结构由γ相中弥散分布大量γ'相构成。为提高合金高温服役的稳定性,合金中加入了十种以上合金强化元素。添加的合金元素对合金的相结构、缺陷结构的作用直接决定合金的高温性能。研究各个合金元素的强化机理,给出具有最佳服役性能时的微观相结构和缺陷结构,确定最佳熔炼工艺、加工工艺、热处理工艺,是得到优质单晶镍基高温合金的主要途径。本论文利用原位电子显微学、原位X射线衍射等测试分析技术,对镍基单晶高温合金DD5在近服役条件下的高温氧化、高温时效、相界面迁移、重要合金元素与缺陷的交互作用、显微结构演化与合金的性能进行了研究,具体研究内容如下:(1)原位研究镍基单晶高温合金高温低压氧化过程:在环境透射电子显微镜(TEM)中利用加热样品台原位测试研究镍基单晶高温合金DD5在850℃、氧压5*10-2Pa条件下,两相氧化过程和氧化诱导的γ'相转变为γ相过程。高分辨TEM、选区电子衍射(SAED)、X射线能量色散谱(EDS)、电子能量损失谱(EELS)等测试分析研究表明γ'相低压氧化产物为尺寸约1～3nm、取向与原 γ'相共格的γ-Al_2O_3纳米晶,与原有相共格关系为(111)γ-Al_2O_3//(001)γ',[1(?)0]γ-Al_2O_3//[1(?)0]γ'或[110]γ-Al_2O_3//[(?)(?)0]γ;γ相低压氧化产物主要为疏松NiO纳米颗粒。从纳米尺度上证明:氧化过程中γ'相有序结构随着γ-Al_2O_3的产生被逐渐破坏,即γ'相中的A1元素被氧化导致γ'-Y相变。同时分析研究证明了高温合金中氧优先扩散通道为Y/Y'相界面。(2)实现了对时效过程中的镍基单晶高温合金晶体结构演变的表征。通过原位高温X射线衍射(XRD)试验发现,随温度升高γ与γγ相晶格常数迅速升高,错配度绝对值逐渐减小;在保温时效过程中,随着时效时间的延长,合金中溶质元素发生再分配会导致γ与γ'相晶格常数略微增加,但合金中γ/γ,相界面的错配度基本无变化。(3)发展了一种新型制备块体材料原位芯片加热TEM样品的方法:在聚焦离子束加工仪(FIB)中将TEM样品中适合观察的区域转移至加热芯片上,保证了原位观察样品薄区大、镓离子污染较少且变温过程中较稳定。对于需要预先甄选样品形貌的原位试验,该方法可大大缩短制样周期。该方法也适用于其他导电块体材料。(4)原位研究相界面与相界面位错在相界面迁移过程中的交互作用:利用原位加热样品台在球差校正电镜中,直接测试分析温度变化时γ/γ'相界面的迁移行为,证明了相界面迁移会导致相界面位错发生位置和形态的改变,但位错始终位于界面上不会逃逸;相界面与单根界面位错的交互作用产生的相界面凹槽为尖角状,表明位错对相界面的影响范围较窄;结合位错核成分分析,本文提出一种新型相界面凹槽形成机制,界面位错附近偏聚的铼元素能够有效阻碍γ相中的γ'相形成元素Ni和A1扩散至γ'相,阻碍相界面迁移,进而在相界面附近形成凹槽。(5)关键合金元素铼在镍基单晶高温合金DD5界面位错网络成分分布:结合高分辨扫描透射电子显微像(STEM)和Super-X对界面位错核心成分进行定量测试分析,确定铼元素偏聚于位错核心;发现热处理条件可调控镍基单晶高温合金相界面位错核心铼偏聚的浓度:a)冷却速度越慢,铼浓度越高;b)时效时长对界面位错核铼浓度分布区间影响不大,但会降低位错核之间铼浓度差别,即界面位错核铼分布更均匀;c)高温时效后先缓冷后回炉能够大大缩短将相界面位错核铼浓度提升至一定数值所需时间。(6)原位研究了铼元素偏聚于界面位错核对镍基单晶高温合金性能的影响:在TEM中利用原位力学样品台研究了相界面位错核心铼浓度不同的样品中位错的行为,发现铼偏聚于界面位错核能够显著强化γ/γ'相界面。位错核低铼的相界面对位错运动阻碍作用较弱,位错易剪切相界面;而位错核高铼的相界面对位错运动的阻碍作用显著,位错运动局限于γ相内,剪切相界面较难。分子动力学和Monte Carrlo模拟计算研究表明铼偏聚对位错结构影响较小,能大幅降低界面位错能量(加入30wt.%铼后,位错每纳米长度能量下降152.7eV),稳定界面位错网络,并使位错附近弹性应力场复杂化,影响运动位错行为。本文对镍基单晶高温合金DD5高温氧化、高温时效、相界面迁移、铼与界面位错交互作用的研究,可为进一步研究高温服役时合金显微组织演变和强化机理提供试验依据,为优化合金微观结构、热处理工艺、优化合金成分、提高合金性能提供路线途径。
[Abstract]:Nickel based single crystal superalloy is the preferred structural material widely used in aero engine turbine blades. Its working characteristics are high temperature and high stress environment. The alloy still maintains excellent mechanical properties at high temperature and depends on its special microstructure. The microstructure of the nickel base single crystal superalloy is composed of a large amount of gamma phase dispersed in the gamma phase. In order to improve the stability of high temperature service of the alloy, more than ten alloying elements are added in the alloy. The effect of alloying elements on the phase structure and defect structure of the alloy determines the high temperature properties of the alloy directly. The strengthening mechanism of the alloying elements is studied, and the microstructure and defect structure with the best service properties are given. The main way to obtain high quality single crystal nickel base superalloy is to determine the best melting process, processing technology and heat treatment process. In this paper, in situ electron microscopy, in situ X ray diffraction and other testing and analysis techniques, the high temperature oxidation, high temperature aging, phase interface migration and important alloy elements of nickel base single crystal superalloy DD5 under the near service condition The interaction of the defects and the microstructure evolution and the properties of the alloys are studied. The specific research contents are as follows: (1) the in situ study of the high temperature and low temperature oxidation process of nickel base single crystal superalloy at high temperature and low pressure: in the environment transmission electron microscope (TEM), the nickel base single crystal superalloy DD5 was studied by the heating sample table in situ, and the oxygen pressure 5*10-2Pa strip was studied at the temperature of the nickel base single crystal superalloy. The two phase oxidation process and the oxidation induced gamma phase transition to gamma phase process. High resolution TEM, selective electron diffraction (SAED), X ray energy dispersive spectrum (EDS), electron energy loss spectrum (EELS) and other tests show that gamma phase low pressure oxidation product is a gamma -Al_2O_3 nanocrystalline with a size of about 1 to 3nm, and a common lattice of the original gamma phase. The lattice relation is (111) gamma -Al_2O_3// (001) gamma ', [1 (?) 0] gamma -Al_2O_3//[1 (?) 0] gamma or [110] gamma -Al_2O_3//[(?) 0] gamma; the low-pressure oxidation products of the gamma phase are mainly loose NiO nanoparticles. It is proved from the nanoscale that the ordered structure of gamma phase in the oxidation process is gradually destroyed with the production of gamma -Al_2O_3, that is, the A1 element in the gamma phase is oxidized to gamma'-Y phase. The study shows that the oxygen preferential diffusion channel in the superalloy is Y/Y'phase interface. (2) the crystal structure evolution of the nickel base single crystal superalloy in the aging process is characterized. The lattice constant of the gamma and gamma phase increases rapidly with the temperature rising, and the absolute value of the mismatch degree decreases gradually. In the process of aging and aging, with the prolongation of aging time, the redistribution of the solute elements in the alloy leads to a slight increase in the lattice constant of gamma and gamma, but the mismatch degree of the phase interface in the alloy is basically unchanged. (3) a new method of heating TEM samples by a new type of block material in situ chip is developed: in the focusing ion beam processing instrument (FIB) the area of the suitable observation in the TEM sample is transferred to the heating chip to ensure that the in situ observation sample thin area is large, the gallium ion pollution is less and the temperature changing process is more stable. In situ test for the selection of sample morphology in advance, this method can greatly shorten the sample preparation period. This method is also suitable for other conductive block materials. (4) in situ The interaction of phase interface and phase interface dislocation in the process of phase interface migration is studied. Using in situ heating sample table in spherical aberration mirror, the migration behavior of gamma / gamma interface is directly measured and analyzed. It is proved that phase interface migration will lead to dislocation position and shape change of phase interface dislocation, but the dislocation is always located in the interface. There is no escape, and the interphase interface with the single interface dislocation has a sharp angle, indicating that the dislocation has a narrow influence on the phase interface. In combination with the analysis of the dislocation nuclei, a new type of phase interface groove formation mechanism is proposed, and the rhenium in the vicinity of the interface dislocation can effectively impede the gamma phase in the gamma phase. The elements Ni and A1 diffuse to the gamma 'phase, obstruct the migration of the phase interface, and then form a groove near the phase interface. (5) the key alloying element rhenium is distributed in the interface dislocation network of the nickel base single crystal superalloy DD5 interface: the quantitative test and analysis of the core components of the boundary dislocation with the high-resolution scanning transmission electron microscope (STEM) and Super-X are used to determine the rhenium. It is found that the heat treatment conditions can regulate the concentration of rhenium at the core of the interface dislocation at the interface of the nickel base single crystal superalloy: a) the slower the cooling rate, the higher the rhenium concentration, and the time of B), which have little influence on the distribution of the rhenium concentration in the dislocation nuclei, but it will reduce the rhenium concentration difference between the dislocation nuclei, that is, the distribution of the rhenium in the interface dislocation nuclei is more uniform. C) the time required to improve the concentration of the dislocation nuclear rhenium to a certain value after the first slow cooling after high temperature aging. (6) the effect of the rhenium element on the properties of the nickel based single crystal superalloy at the interface dislocation nucleation was investigated in situ: in the TEM, the concentration of rhenium at the core of the phase dislocation in the phase interface is different. The behavior of dislocation in the sample shows that rhenium segregation at the dislocation nucleus can significantly strengthen the interface of gamma / gamma phase. The phase boundary of the dislocations is weak and the dislocation is easy to shear phase interface, while the phase boundary of the high rhenium in the dislocation nucleus is significantly hindered by the dislocation motion, and the dislocation movement is confined to the gamma phase, and the shear phase interface is difficult. The study of molecular dynamics and Monte Carrlo simulation shows that rhenium segregation has little influence on dislocation structure, and can greatly reduce the interface dislocation energy (after adding 30wt.% rhenium, the dislocation per nanometer energy drop 152.7eV), stabilize the interface dislocation network, and compound the elastic stress field near the dislocation, and affect the motion dislocation behavior. The study of high temperature oxidation, high temperature aging, phase interface migration and the interaction of rhenium with interface dislocation can provide experimental basis for further research on microstructure evolution and strengthening mechanism of alloy at high temperature service, and provide a route for optimizing alloy microstructure, heat treatment process, optimizing alloy composition and improving alloy properties DD5.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG132.3
本文编号：2140417
[Abstract]:Nickel based single crystal superalloy is the preferred structural material widely used in aero engine turbine blades. Its working characteristics are high temperature and high stress environment. The alloy still maintains excellent mechanical properties at high temperature and depends on its special microstructure. The microstructure of the nickel base single crystal superalloy is composed of a large amount of gamma phase dispersed in the gamma phase. In order to improve the stability of high temperature service of the alloy, more than ten alloying elements are added in the alloy. The effect of alloying elements on the phase structure and defect structure of the alloy determines the high temperature properties of the alloy directly. The strengthening mechanism of the alloying elements is studied, and the microstructure and defect structure with the best service properties are given. The main way to obtain high quality single crystal nickel base superalloy is to determine the best melting process, processing technology and heat treatment process. In this paper, in situ electron microscopy, in situ X ray diffraction and other testing and analysis techniques, the high temperature oxidation, high temperature aging, phase interface migration and important alloy elements of nickel base single crystal superalloy DD5 under the near service condition The interaction of the defects and the microstructure evolution and the properties of the alloys are studied. The specific research contents are as follows: (1) the in situ study of the high temperature and low temperature oxidation process of nickel base single crystal superalloy at high temperature and low pressure: in the environment transmission electron microscope (TEM), the nickel base single crystal superalloy DD5 was studied by the heating sample table in situ, and the oxygen pressure 5*10-2Pa strip was studied at the temperature of the nickel base single crystal superalloy. The two phase oxidation process and the oxidation induced gamma phase transition to gamma phase process. High resolution TEM, selective electron diffraction (SAED), X ray energy dispersive spectrum (EDS), electron energy loss spectrum (EELS) and other tests show that gamma phase low pressure oxidation product is a gamma -Al_2O_3 nanocrystalline with a size of about 1 to 3nm, and a common lattice of the original gamma phase. The lattice relation is (111) gamma -Al_2O_3// (001) gamma ', [1 (?) 0] gamma -Al_2O_3//[1 (?) 0] gamma or [110] gamma -Al_2O_3//[(?) 0] gamma; the low-pressure oxidation products of the gamma phase are mainly loose NiO nanoparticles. It is proved from the nanoscale that the ordered structure of gamma phase in the oxidation process is gradually destroyed with the production of gamma -Al_2O_3, that is, the A1 element in the gamma phase is oxidized to gamma'-Y phase. The study shows that the oxygen preferential diffusion channel in the superalloy is Y/Y'phase interface. (2) the crystal structure evolution of the nickel base single crystal superalloy in the aging process is characterized. The lattice constant of the gamma and gamma phase increases rapidly with the temperature rising, and the absolute value of the mismatch degree decreases gradually. In the process of aging and aging, with the prolongation of aging time, the redistribution of the solute elements in the alloy leads to a slight increase in the lattice constant of gamma and gamma, but the mismatch degree of the phase interface in the alloy is basically unchanged. (3) a new method of heating TEM samples by a new type of block material in situ chip is developed: in the focusing ion beam processing instrument (FIB) the area of the suitable observation in the TEM sample is transferred to the heating chip to ensure that the in situ observation sample thin area is large, the gallium ion pollution is less and the temperature changing process is more stable. In situ test for the selection of sample morphology in advance, this method can greatly shorten the sample preparation period. This method is also suitable for other conductive block materials. (4) in situ The interaction of phase interface and phase interface dislocation in the process of phase interface migration is studied. Using in situ heating sample table in spherical aberration mirror, the migration behavior of gamma / gamma interface is directly measured and analyzed. It is proved that phase interface migration will lead to dislocation position and shape change of phase interface dislocation, but the dislocation is always located in the interface. There is no escape, and the interphase interface with the single interface dislocation has a sharp angle, indicating that the dislocation has a narrow influence on the phase interface. In combination with the analysis of the dislocation nuclei, a new type of phase interface groove formation mechanism is proposed, and the rhenium in the vicinity of the interface dislocation can effectively impede the gamma phase in the gamma phase. The elements Ni and A1 diffuse to the gamma 'phase, obstruct the migration of the phase interface, and then form a groove near the phase interface. (5) the key alloying element rhenium is distributed in the interface dislocation network of the nickel base single crystal superalloy DD5 interface: the quantitative test and analysis of the core components of the boundary dislocation with the high-resolution scanning transmission electron microscope (STEM) and Super-X are used to determine the rhenium. It is found that the heat treatment conditions can regulate the concentration of rhenium at the core of the interface dislocation at the interface of the nickel base single crystal superalloy: a) the slower the cooling rate, the higher the rhenium concentration, and the time of B), which have little influence on the distribution of the rhenium concentration in the dislocation nuclei, but it will reduce the rhenium concentration difference between the dislocation nuclei, that is, the distribution of the rhenium in the interface dislocation nuclei is more uniform. C) the time required to improve the concentration of the dislocation nuclear rhenium to a certain value after the first slow cooling after high temperature aging. (6) the effect of the rhenium element on the properties of the nickel based single crystal superalloy at the interface dislocation nucleation was investigated in situ: in the TEM, the concentration of rhenium at the core of the phase dislocation in the phase interface is different. The behavior of dislocation in the sample shows that rhenium segregation at the dislocation nucleus can significantly strengthen the interface of gamma / gamma phase. The phase boundary of the dislocations is weak and the dislocation is easy to shear phase interface, while the phase boundary of the high rhenium in the dislocation nucleus is significantly hindered by the dislocation motion, and the dislocation movement is confined to the gamma phase, and the shear phase interface is difficult. The study of molecular dynamics and Monte Carrlo simulation shows that rhenium segregation has little influence on dislocation structure, and can greatly reduce the interface dislocation energy (after adding 30wt.% rhenium, the dislocation per nanometer energy drop 152.7eV), stabilize the interface dislocation network, and compound the elastic stress field near the dislocation, and affect the motion dislocation behavior. The study of high temperature oxidation, high temperature aging, phase interface migration and the interaction of rhenium with interface dislocation can provide experimental basis for further research on microstructure evolution and strengthening mechanism of alloy at high temperature service, and provide a route for optimizing alloy microstructure, heat treatment process, optimizing alloy composition and improving alloy properties DD5.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG132.3
【参考文献】
相关期刊论文 前3条
1 ;Measurements of γ/γ' Lattice Misfit and γ' Volume Fraction for a Ru-containing Nickel-based Single Crystal Superalloy[J];Journal of Materials Science & Technology;2011年10期
2 骆宇时;刘世忠;孙凤礼;;铼在单晶高温合金中强化机理的研究现状[J];材料导报;2005年08期
3 ;Effects of Rhenium on Creep Rupture Life of a Single Crystal Superalloys[J];Journal of Materials Science & Technology;1999年01期
，本文编号：2140417
本文链接：https://www.wllwen.com/shoufeilunwen/gckjbs/2140417.html
