Ru合金化Ni/Ni3Al相界断裂功的第一原理计算

采用第一原理赝势平面波方法计算了Ru合金化前后γ-Ni／γ＇-Ni3Al相界的电子与能态结构,并比较强化元素Ru分别占据不同亚点阵位时对相界断裂强度的影响。结果表明：Ru置换Ni／Ni3AI相界区域中的Ni或Al原子,都可明显提高Ni／Ni3Al相界的断裂强度;尤其以Ru置换γ-Ni／γ＇-Ni3Al相界界面层的Al原子时,对相界的强化效果最好。电子态密度与电子密度分布图的分析结果显示：Ru合金化对γ-Ni／γ＇-Ni3Al相界的强化可归因于Ru与其最近邻Ni原子间强烈的电子相互作用引起的相界区域层间原子价键强度的增强。     

N在γ-Ni/γ′-Ni3Al相界区域的占位趋势与脆化作用

采用第一原理赝势平面波方法研究迹量元素N在γ-Ni/γ′-Ni3Al相界区域的占位趋势及其对相界断裂强度的影响。结果显示:以气态形式存在的N不易掺杂到Ni/Ni3Al相界,而以固态形式存在的N则很容易被掺进Ni/Ni3Al相界;N在Ni/Ni3Al相界中不仅能稳定存在,而且掺杂到八面体间隙比置换其中的基体原子具有更高的形成能力与结构稳定性;N掺杂将削弱Ni/Ni3Al相界的断裂强度,其中尤以间隙位掺杂最为明显。电子结构分析表明:置换型掺杂时,相界断裂强度的降低可归结为Frenkel缺陷导致的掺杂相界层间电子相互作用的减弱;而间隙位掺杂,除了基体原子间电子相互作用因掺杂原子与基体原子间的强相互作用而减弱外,晶格畸变导致的局域弹性应变能增加也是一个重要的原因。     

N在γ-Ni/γ'-Ni3Al相界区域的占位趋势与脆化作用

采用第一原理赝势平面波方法研究迹量元素N在γ-Ni/γ’-Ni3Al相界区域的占位趋势及其对相界断裂强度的影响.结果显示:以气态形式存在的N不易掺杂到Ni/Ni3Al相界,而以固态形式存在的N则很容易被掺进Ni/Ni3Al相界;N在Ni/Ni3Al相界中不仅能稳定存在,而且掺杂到八面体间隙比置换其中的基体原子具有更高的形成能力与结构稳定性;N掺杂将削弱Ni/Ni3Al相界的断裂强度,其中尤以间隙位掺杂最为明显.电子结构分析表明:置换型掺杂时,相界断裂强度的降低可归结为Frenkel缺陷导致的掺杂相界层间电子相互作用的减弱;而间隙位掺杂,除了基体原子间电子相互作用因掺杂原子与基体原子间的强相互作用而减弱外,晶格畸变导致的局域弹性应变能增加也是一个重要的原因.     

Ni基合金γ/γ''相界Ir合金化时结构特性的第一原理研究

采用非相对论第一原理分子轨道DV-Xa模型簇方法,计算了Ni基单晶超合金γ/γ'相界的电子结构,并从键重叠聚居数(QAB)、界面原子层间的部分键合强度,以及界面原子局域环境总键合强度几个方面,对Ir合金化前后γ/γ'界面的结构稳定性、脆化特性、相间断裂的难易程度等几个方面对γ/γ'相界的结构特性进行了分析.结果表明:Ir合金化能增强γ/γ'界面Ni-Ni与Ni-Al原子间的键合强度,价键强度的增加有如下的变化趋势:QNi-Ni＜QNi-Al＜QIr-Ni＜QIr-Al,相界上,当被置换原子的种类与位置不同时,Ir合金化对γ/γ'相界结构性能的影响程度也不相同,比较而言,Ir置换γ相中的Ni最有利于提高γ/γ'相界的结构稳定性与相间抗断强度.     

Ni基合金γ／γ′相界Ir合金化时结构特性的第一原理研究

采用非相对论第一原理分子轨道DV-Xα模型簇方法,计算了Ni基单晶超合金γ/γ'相界的电子结构,并从键重替聚居数(QAB)、界面原子层间的部分键合强度,以及界面原子局域环境总键合强度几个方面,对Ir合金化前后γ/γ'界面的结构稳定性、脆化特性、相间断裂的难易程度等几个方面对γ/γ'相界的结构特性进行了分析。结果表明:Ir合金化能增强γ/γ'界面Ni-Ni与Ni-Al原子间的键合强度,价键强度的增加有如下的变化趋势:QNi-Ni相似文献   

Effect of Y2O3 on microstructure and oxidation of γ-Ni+γ'-Ni3Al coatings transformed from electrodeposited Ni-Al films at 1 000 ℃

The electrodeposited Y2O3-dispersed γ-Ni γ'-Ni3Al coatings on Ni substrates were developed by the conversion of electrodeposited Ni-Al-Y2O3 films with dispersed Al microparticles in Ni matrix into Ni3Al by vacuum annealing at 800 ℃ for 3 h. For comparison, Y2O3-free (γ-Ni γ'-Ni3Al coatings with a similar Al content were also prepared by vacuum annealing the electrodeposited microparticle-dispersed composite coatings of Ni-Al under the same condition. SEM and TEM characterizations show that the electrodeposited Y2O3-dispersed γ γ' coatings exhibit finer grains, a more homogeneous distribution of γ', and a narrowed γ' phase spacing compared with the electrodeposited Y2O3-free γ γ' coatings. The oxidation at 1 000 ℃ shows that the addition of Y2O3 significantly improves the oxidation resistance of the electrodeposited γ γ'coatings. The effect of Y2O3 particles on the microstructure and oxidation behavior of the electrodeposited γ γ' coatings was discussed in detail.     

W对Co-Al-W合金相界强度影响的理论研究

基于第一性原理赝势平面波方法,研究了W掺杂γ-Co/γ′-Co_3Al相界前后其对电子分布与能态结构的变化。相界断裂功计算结果表明,W原子取代界面内γ′-Co_3Al相区中的Al原子可提高γ-Co/γ′-Co_3Al相界的断裂强度,而取代其他位置的Al原子或Co原子时,对其相界区域断裂强度的影响则不明显。进一步通过分析电子态密度与电子密度分布图发现,W的掺杂使其与最近邻Co原子间所产生的强烈电子相互作用,将引起相界区域层间原子成键相互作用增强,这是γ-Co/γ′-Co_3Al相界断裂强度得到提高的直接原因。     

镍基高温合金长期时效后元素分布规律研究

采用原子探针仪器LEAP 4000X Si,研究镍基高温合金Ni-Al-Cr-W-Re-Ru长期时效后的元素分布规律。结果表明,Ni、Cr和Re原子在无序γ(fcc)-基体相中富集,而Al和W原子更多分配到有序γ'(L1_2)-析出相。在γ/γ'相界面γ相一侧出现Ni原子局部富集,导致界面自由能降低。γ'相中,溶质元素原子浓度总和约25at%,实验局部Al-R(R=Re、Ru或W)RDF在第1最近邻距离处负相关,说明Re、Ru和W优先占据Ni3Al(L1_2)结构的Al位。和三元合金Ni-Al-Cr相比,添加W、Re和Ru后,合金的γ相得到固溶强化,γ'相体积分数提高,硬度增加。     

Pt+g ￠-Ni3Al+g-Ni/CMSX-4涂层结构的透射电镜研究

通过在CMSX-4镍基单晶高温合金表面镀Pt然后采用包埋渗铝的方法成功制备Pt改性的Pt+γ′-Ni3Al+γ-Ni/CMSX-4涂层,采用扫描电镜和透射电镜研究Pt+γ′-Ni3Al+γ-Ni/CMSX-4涂层的微观结构。TEM分析表明Pt主要分布于涂层γ′-Ni3Al相中,且涂层γ′-Ni3Al相里存在{111}孪晶;此外涂层内还发现六方结构富铼的拓扑密堆相(μ相),点阵常数为a=0.473nm和c=2.565nm,首次发现μ相内除了(001)孪晶外还存在(102)孪晶;探讨μ相和孪晶的形成机制。     

Pt+γ′-Ni_3Al+γ-Ni/CMSX-4涂层结构的透射电镜研究

通过在CMSX-4镍基单晶高温合金表面镀Pt然后采用包埋渗铝的方法成功制备Pt改性的Pt+γ′-Ni3Al+γ-Ni/CMSX-4涂层,采用扫描电镜和透射电镜研究Pt+γ′-Ni3Al+γ-Ni/CMSX-4涂层的微观结构。TEM分析表明Pt主要分布于涂层γ′-Ni3Al相中,且涂层γ′-Ni3Al相里存在{111}孪晶;此外涂层内还发现六方结构富铼的拓扑密堆相(μ相),点阵常数为a=0.473nm和c=2.565nm,首次发现μ相内除了(001)孪晶外还存在(102)孪晶;探讨μ相和孪晶的形成机制。     

5d过渡金属在Ni3Al中掺杂效应的第一性原理研究

5d过渡金属Hf、Ta、W、Re、Ir被广泛地应用于第4、5代镍基单晶高温合金中,但对于其机理却没有系统的理论研究。采用基于密度泛函理论(density functional theory)的第一性原理平面波超软赝势方法研究5d过渡金属Hf、Ta、W、Re、Ir掺杂镍基单晶高温合金γ′-Ni3Al相前后系统的晶格常数、形成热、结合能、态密度、差分电荷密度及电荷布局。计算结果表明:5d过渡金属Hf、Ta、W、Re、Ir掺杂Ni3Al系统后有优先占据Al原子位置的倾向,且与周围的Ni 3d电子和Al 3p电子发生强烈的轨道杂化,使电子被束缚,离域性变小,峰变窄;掺杂前系统中主要是Ni原子与最近的Al原子之间的共价键作用,掺杂后系统中主要是Ni原子与最近的X原子(Hf、Ta、W、Re、Ir)之间的共价键作用,且随原子序数的增大共价键逐渐增强。     

合金元素对Ni3Al（010）面反相畴界能影响的第一性原理研究

采用第一性原理投影缀加波赝势和广义梯度近似方法研究不同铝含量以及主要合金化元素Ti、Mo、Ru、Pd、Ta、W、Re和Pt等对Ni3Al(010)面反相畴界能的影响规律,并结合合金元素与第一近邻原子的相互作用关系对其进行讨论。结果表明:随着铝含量的增加,Ni3Al(010)面的反相畴界能显著升高;在富镍条件下,优先占据Ni3Al镍亚点阵位置的合金元素Ru、Pd和Pt会降低Ni3Al(010)面的反相畴界能,而优先占据Ni3Al铝亚点阵位置的合金元素Ti、Mo、Ta、W和Re则会增大Ni3Al(010)面的反相畴界能;合金元素对Ni3Al反相畴界能的影响既与该合金元素在化合物中亚点阵的优先占位相关,又与该合金元素与化合物中Ni与Al原子的键合强度相关。     

Diffusion barrier behaviors of (Ru,Ni)Al/NiAl coatings on Ni-based superalloy substrate

For Ni-based single crystalline superalloy with high temperature protective coatings, the formation of detrimental phases in the superalloy substrate resulting from interdiffusion between the coatings and the substrate significantly degrades the mechanical properties of the substrate. In this paper, a novel (Ru,Ni)Al/NiAl diffusion barrier coating was produced by electrodeposition of Ru together with electron beam-physical vapor deposition of Ni–Al layer. The microstructure and diffusion barrier behavior of the (Ru,Ni)Al/NiAl coating was investigated by scanning electron micrograph (SEM) equipped with energy dispersive spectroscopy (EDS). SRZ mainly consisting of P phase and other TCP phases were presented beneath the NiAl coating due to the interdiffusion between the coating and Ni-based superalloy. The (Ru,Ni)Al layer effectively slowed down inward diffusion of Al from the coating and outward diffusion of alloying elements such as W and Mo, therefore suppressed the formation of TCP phases and SRZ.     

Microscopic phase-field modeling of atomic anti-site behaviors in precipitation progress of Ni3(AlFe)

The effects of temperature on atomic anti-site behaviors in L12-Ni3(AlFe) phases were studied using microscopic phase-field dynamic model in precipitation progress of Ni75Al20Fe5 alloy.The results show that with the increase of temperature,the formation of NiAl and AlNi anti-sites is much easier in Ni3(AlFe),and Ni and Al anti-site atoms show clearly stronger temperature-dependent than Fe anti-site atoms.The evolution progress of anti-site atoms is completed at the initial growth stage of L12-Ni3(AlFe) phases.The site occupation probabilities of Ni atoms on the sublattice A(NiNi,face centers sites of FCC),and Al and Fe atoms on the sublattice B(AlAl and FeAl,corners sites of FCC) all present the degressive tendency with the temperature increasing.Fe atoms mainly prefer to occupy the Al sublattice at the whole temperature range.     

Synergistic effect of co-alloying elements on site preferences and elastic properties of Ni3Al: A first-principles study

The site preferences of co-alloying elements (Mo–Ta, Mo–Re, Mo–Cr) in Ni₃Al are studied using first-principles calculations, and the effects of these alloying elements on the elastic properties of Ni₃Al are evaluated by elastic property calculations. The results show that the Mo–Ta, Mo–Re and Mo–Cr atom pairs all prefer Al–Al sites and the spatial neighbor relation of substitution sites almost has no influence on the site preference results. Furthermore, the Young's modulus of Ni₃Al increases much higher by substituting Al–Al sites with co-alloying atoms, among which Mo–Re has the best strengthening effect. The enhanced chemical bondings between alloying atoms and their neighbor host atoms are considered to be the main strengthening mechanism of the alloying elements in Ni₃Al.     

机械合金化制备TiB2-Ni(Al)复合粉末组织结构研究

目的通过原位合成技术获得TiB_2-Ni(Al)复合粉末。方法采用机械合金化方法在不同球磨时间的条件下,制备不同体积含量的TiB_2陶瓷相增强Ni(Al)基复合粉末,其中Ni粉和Al粉的摩尔比为1:1。采用扫描电子显微镜(SEM)以及X-射线衍射仪(XRD)分析球磨后粉末的显微组织结构及物相,研究不同球磨时间对制备TiB_2-Ni(Al)复合粉末物相演变、组织结构及粒子间界面结合状态的影响。结果在球磨过程中,球磨时间越长,Ni/Al间的塑变有利于原子之间的扩散,TiB_2陶瓷相颗粒逐渐变小。当球磨时间增长到一定程度时,延展性好的Al粉颗粒发生扁平化且其表面积不断增大,使得碎化后的Ni粉颗粒不断嵌入Al粉颗粒中,最终形成Ni(Al)固溶体。同时根据XRD分析发现,随着球磨时间的延长,TiB_2-Ni(Al)复合粉末中的Al峰逐渐减小,说明Al不断固溶到Ni中,形成了一定量的Ni(Al)固溶体。结论通过机械球磨技术在球磨一定时间后可原位合成Ni(Al)固溶体,这说明随着Ni与Al之间的相互扩散有利于形成Ni(Al)固溶体。     

Effect of Stand-Off Distance on the Microstructure and Mechanical Properties of Ni/Al/Ni Laminates Prepared by Explosive Bonding

Ni/Al laminates are of great interest in many aerospace and military applications due to their excellent mechanical properties. However, their application has been limited in part due to challenges related to fabricating complex geometries. However, explosive welding is regarded as a promising technique to fabricate laminates. However, it is difficult to fabricate Ni/Al/Ni laminates with high interfacial shear strength and ductility if the stand-off distance has not been optimized during the explosion process. The goal of this study was to investigate the effect of stand-off distance on the microstructure and mechanical properties of Ni/Al/Ni laminates, and SEM and EDS were used to characterize the morphology and element distribution of the double layer interface. Tensile and tensile-shear tests were conducted to evaluate the mechanical properties of the laminates. The results indicated that with the increase in stand-off distance, three different kinds of interface were obtained (straight, wavy and continuously melted). Thickness of atomic diffusion layer increased with the increase in stand-off distance. Moreover, the Ni/Al/Ni laminates with wavy interface possessed highest value of ductility and interfacial bonding strength.     

L12相间有序畴界成分的微观相场研究

利用微观相场模型研究了有序畴界结构、合金成分和弹性应变能对Ni75AlxV25-x合金中L12-Ni3Al相间有序畴界成分的影响规律。结果表明:L12相间形成的3种有序畴界中,在(100)//(200)·[001]处,Ni的贫化程度最小,Al的贫化程度最大,V的偏聚程度最大;在(200)//(200)处,Ni的贫化程度最大,Al的贫化程度最小,V的偏聚程度最小。随着合金中Al浓度的增加,3种有序畴界处Ni的浓度降低,Al的浓度升高,V的浓度降低。弹性应变能使得L12相间3种有序畴界处Ni和Al的浓度升高,V浓度降低。但弹性应变能对(200)//(200)·[001]和(100)//(200)·[001]成分的影响较大,对(200)//(200)成分的影响则相对较小。     

A first-principles study on interfacial properties of Ni(001)/Ni3Nb(001)

The Ni (001) surface, Ni₃Nb (001) surface and Ni (001)/Ni₃Nb (001) interfaces were studied using the first-principles pseudopotential plane-wave method. The adhesion work, thermal stability and electronic structure of Ni/Ni₃Nb (001) interfaces were calculated to expound the influence of atom termination and stacking sequence on the interface strength and stability. Simulated results indicate that Ni and Ni₃Nb (001) surface models with more than eight atomic layers exhibit bulk-like interior. The (Ni+Nb)-terminated interface with hollow site stacking has the largest cohesive strength and critical stress for crack propagation and the best thermal stability among the four models. This interfacial Ni and the first nearest neighbor Nb atoms form covalent bonds across the interface region, which are mainly contributed by Nb 4d and Ni 3d valence electrons. By comparison, the thermal stability of Ni/Ni₃Nb (001) interfaces is worse than Ni/Ni₃Al (001) interface, implying that the former is harder to form. But the Ni/Ni₃Nb interface can improve the mechanical properties of Ni-based superalloys.     

FASHS技术制备TiB2+Ni/Ni3Al/405不锈钢梯度材料

采用电场激活自蔓延高温合成(FASHS)技术制备了TiB2 Ni/Ni3Al/405不锈钢梯度材料.试验中首先将镍粉和铝粉球磨处理以促进燃烧反应发生,然后采用FASHS技术利用自蔓延燃烧反应热连接制备了TiB2 Ni/Ni3Al/405不锈钢梯度材料.用SEM和XRD分析了梯度材料各层的界面微观组织及相组成,用洛氏硬度计、显微硬度计及磨料磨损试验机分析了材料的力学性能、硬度及表面抗磨性.结果表明,金属陶瓷复合层、Ni3Al层和405不锈钢金属片间形成了可靠的冶金结合,金属陶瓷复合材料表面硬度为90HRA,材料的化学成分和显微硬度呈梯度分布,耐磨性优于20Cr渗碳钢.