Surface diffusivity of atomic deuterium on Ni3（Al,Ti）（110）surface with and without boron

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｗｅｌｌａｃｃｅｐｔｅｄｔｈａｔｍｏｉｓｔｕｒｅ ｉｎｄｕｃｅｄｅｍｂｒｉｔ ｔｌｅｍｅｎｔｉｓｔｈｅｍａｊｏｒｃａｕｓｅｏｆｔｈｅｌｏｗｄｕｃｔｉｌｉｔｙａｎｄｉｎ ｔｅｒｇｒａｎｕｌａｒｆａｉｌｕｒｅｏｆＮｉ3Ａｌａｎｄ     

SURFACE REACTION，HYDROGEN DIFFUSIVITY AND ENVIRONMENTAL EMBRITTLEMENT OF INTERMETALLIC COMPOUNDS Ni_3Al AND Fe_3Al

ＳＵＲＦＡＣＥＲＥＡＣＴＩＯＮ，ＨＹＤＲＯＧＥＮＤＩＦＦＵＳＩＶＩＴＹＡＮＤＥＮＶＩＲＯＮＭＥＮＴＡＬＥＭＢＲＩＴＴＬＥＭＥＮＴＯＦＩＮＴＥＲＭＥＴＡＬＬＩＣＣＯＭＰＯＵＮＤＳＮｉ_３ＡｌＡＮＤＦｅ_３ＡｌＷＡＮＸｉａｏｊｉｎｇ；ＺＨＵＪｉａｈｏｎｇ；...     

Interaction of H2O and O2 with Ni3Fe and their effects on ductility

Possible reasons for the high ductility of Ni₃Fe and its insensitivity toward the testing environment have been investigated. Thermal desorption experiments have shown that water dissociates on clean Ni₃Fe surfaces to produce atomic hydrogen. Ductility measurements of cast and cold-rolled polycrystalline Ni₃Fe demonstrated that the reduced ductility was obtained only when the testing was performed with oxygen carefully removed. X-ray photoemission studies indicate that oxygen interacts with water to form hydroxyls, thereby suppressing the production of atomic hydrogen. Hydrogen desorption from the Ni₃Fe surface requires a lower activation energy, resulting in a smaller surface hydrogen concentration at a given temperature. Hence it is possible that there is insufficient hydrogen to cause the nucleation and growth of brittle cracks for severe embrittlement.     

复相Al2O3/SiCw陶瓷与不锈钢钎焊接头的界面反应和反应产物

采用氩气保护下活性金属钎焊法对碳化硅晶须增韧氧化铝陶瓷（Al2O3/SiCw）与不锈钢（1Cr18Ni9Ti)进行了钎焊，所用钎料为Ag-Cu-Ti3活性钎料，通过X－射线衍射仪（XRD）对界面的反应产物进行了物相分析，并用能谱仪（EDAX）分析了界面元素组成，结果表明，钎焊接头界面的反应十分复杂，反应产物多种多样，主要有TiO,Ti2O,TiC,Fe2Ti4O,Ni3Ti,AlTi等物质，界面反应层按Al2O3 SiC/TiO AlTi TiC/TiO2 Fe2Ti4O/Ag-Cu的规律过渡。     

THE EXPERIMENTAL STUDIES OF NiO CLUSTER FORMATION IN Ni_3Al ALLOYS BY AP-FIM

1. IntroductionFOr maily years, the room temperature brittleness of the polyer}l'stalline Ni3AI was recognized to be "intrinsically brittl.5,[1'2] due to brittle grain--boundary fracture. Recentlyit hajs been shown that environmental embrittlement is a major cause of the poor ductiLity of NiaAI in air[3--sl, and the embrittlement mechanism involves chemical .eactio.sfsl=M HzO-MO ZH or M HaO-MOH H. Where M is a reactive element in the intermetallic compound (Ni and Al) which reacts ch…     

Surface spectroscopy and temperature-programmed desorption studies of the interaction of water vapor with Ni3(Al, Ti) (100) and (111) surfaces as a function of temperature

The interaction of water vapor with single crystal Ni₃(Al, Ti) has been studied with Auger electron spectroscopy, photoemission spectroscopy and thermal desorption. Water adsorbs molecularly onto the (111) and (100) surfaces at 140 K. When warmed up to room temperature, water remains as an intact molecule on (111), but dissociates to surface hydroxyl and atomic oxygen on (100). The latter process is accompanied by the evolution of hydrogen and oxidation of Al. It appears that the dissociation of water is structure-sensitive and that Al is the active species in controlling the dissociation of water on Ni₃Al surfaces.     

Properties of Fe-based Amorphous Alloy Coatings with Al2O3-13% TiO2 Deposited by Plasma Spraying

采用大气等离子喷涂技术成功在Fe普碳钢基材上制备了含有不同质量分数Al2O3-13%Ti O2颗粒的Fe基非晶复合涂层,其中Fe基非晶相成分为Fe71Cr5B4Si4Ni3Mo3W10(wt%),并对涂层的微观结构、显微硬度和耐蚀性能进行了研究。在Fe基非晶相与Al2O3-13%Ti O2陶瓷相界面观察到Fe、Ti、W、Al和O元素的互扩散现象,这种微区冶金结合减少了由于第二相的加入导致的涂层孔隙并增加了相间的结合强度。当加入的Al2O3-13%Ti O2质量分数≥16 wt%时,涂层的显微硬度升高≥20%;复合非晶涂层在10 wt%Na OH溶液中的耐腐蚀性能高于1Cr18Ni9Ti不锈钢。     

THE ALLOYING BEHAVIOR OF BORON AND CARBON INNi_3Al

ＴＨＥＡＬＬＯＹＩＮＧＢＥＨＡＶＩＯＲＯＦＢＯＲＯＮＡＮＤＣＡＲＢＯＮＩＮＮｉ３Ａｌ①ＺｈａｎｇＹｕｎ，ＨｕａｎｇＪｉｎ，ＬｉｎＤｏｎｇｌｉａｎｇＳｈａｎｇｈａｉＪｉａｏｔｏｎｇＵｎｉｖｅｒｓｉｔｙ，Ｓｈａｎｇｈａｉ２０００３０ＡＢＳＴＲＡＣＴＴｏｆ...     

Moisture-induced embrittlement mechanism for (Ni,Fe)Ti alloys

Recent experimental studies showed that the ductility of NiTi is not affected by moisture, while addition of iron beyond 9 a/o in NiTi leads to moisture-induced embrittlement. To explore the nature of this embrittlement, we studied the chemical interaction between water vapor and (Ni,Fe)Ti(110) surfaces with 5 a/o and 10 a/o Fe. Temperature-programmed desorption and X-ray photoelectron spectroscopy show that decomposition of water to produce atomic hydrogen occurs on both surfaces. Activation energy for surface diffusion was calculated by density functional theory, showing that addition of Fe decreases H surface diffusivity, in agreement with experiment. Together with the observation that addition of 9 a/o Fe increases the strength of NiTi, this indicates that moisture-induced embrittlement in higher strength NiTi alloys is not due to faster H surface diffusion, but lower critical hydrogen concentration required for embrittlement.     

Microstructures of L2_1/L1_2 multi-phase intermetallics in Co-Ni-Al-Ti system

1　ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｓｈａｖｅｔｈｅ ｐｒｏｍｉｓｅｏｆｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃｔｕｒａｌａｐｐｌｉｃａｔｉｏｎ ,ｗｈｉｌｅｔｈｅｒｏａｄａｈｅａｄｉｓｈｉｎｄｅｒｅｄｂｙｉｔｓｌｏｗｈｉｇｈ ｔｅｍｐｅｒａｔｕｒｅｃｒｅｅｐｒｅｓｉｓｔａｎｃｅａｎｄｐｏｏｒｒｏｏｍ ｔｅｍｐｅｒａｔｕｒｅｄｕｃｔｉｌｉｔｙ .Ｔｈｅ ｐｒｅｖｉｏｕｓｒｅｓｅａｒｃｈｓｕｇｇｅｓｔｅｄｔｈａｔｍｕｌｔｉ ｃｏｍｐｏ ｎｅｎｔａｌｌｏｙｉｎｇｔｏｐｒｏｄｕ…     

SELF-CONSISTENT TOTAL ENERGIES AND ELECTRONIC STRUCTURES OF HYDROGENIZED Ni,Al AND Ni_3Al

By use of the self-consistent method of linear muffin-tin orbitals with the atomic sphere approximation on the basis of densitv functional theory the total energies and the electron- ic structures of Ni,AL,and their hvdrides NiH.AIH and Ni_3AlH are caleulated.The the- oretical excess energies and the lattice strains due to hydrogen absorption consequentlv obtained from the ab initio results indicate that Ni is a better hvdrogen absorber than Al,anthe absorptivity of Ni_3Al dramaticallv decreases owing to the repulsion between Al and H On the other hand,the changes of band structures due to hydrogenation are found to beremparkable except that for Al.and ther are shown to be the qualitative mani(?)estation of existing conclusions form photoemission experiments.     

Study on the Precipitation of gamma ' in a Fe-Ni Base Alloy During Ageing by APTEI北大核心CSCD

High strength Fe-Ni base austenitic alloys, such as A286 and JBK-75, are widely used in gas turbine jet engines and hydrogen service and so on because of their excellent corrosion resistance and low hydrogen embrittlement sensitivity. The ordered coherent gamma' [Ni-3(Al, Ti)], precipitated during ageing, is thought to have the main contribution on the strength. Thus, it is very important to understand the characterization of the precipitation. However, few previous studies are focused on atomic scale evolution of the precipitated phase. Atom probe tomography (APT) is a unique microscopy technique that provides 3D analytical mapping of materials at near atomic resolution and a high detection sensitivity for all elements. The present research is focused on the microstructure evolution at ageing temperature at different time scales using APT. A Fe-Ni base austenite alloy were aged at 620 degrees Cfor different time after solution treated at 980 degrees C for 2 h. Hardness testing indicates that a sharp increase is observed when the ageing time is less than 6 h. The hardness is up to 205 HV from the initial 145 HV at the ageing time 6 h. After that the hardness increases slowly. The hardness is 251 HV at 120 h. APT results reveal that Ti-rich nano-clusters precipitate obviously at the initial stage of ageing, which contain Fe, Cr, Ni, Mo and Al elements. As the ageing time increases, more Ni and Al atoms are segregated in the Ti-rich nanoclusters while the Fe, Cr and Mo are ejected from the nanoclusters. When the ageing time is up to 120 h, the Ni/(Ti+Al) ration is approximately close to 3. The precipitates can be identified as gamma' phase. The results reveal that the formation of gamma' involves nucleation and growth. Effect of the number density and the size of the gamma' precipitates on the hardening of the alloy has been estimated.     

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。     

SURFACE REACTION OF Ni_3Al WITH WATER VAPOR OR OXYGEN

1.IntroductionManyresearcheshavedem0nstratedthatthebrittlefractureandpoorductilityatambienttemperature0fsomeintermetallicc0mp0undsarecausedbytheatmosphereofen.ir0n.entIl-4].Forexample,theel0ngationofFe3Alanditsalloystestedinairwasmuchlowerthanthatinvacuum0roxygenl516].Ni3Al-basedall0yswith0utbor0nandwitha1owcontent0fboronweresh0wnt0bequiteductilewithel0ngati0nof15-25%wl1entestedinvacuum0rpllreoxygen,whi1etheyexhibitedp0orductilityof4-10%inai,[7'8].Thisphenomen0nisbelievedtobeahydrogenembritt…     

TiCx/Ni3Al复合材料相界面显微结构及界面纳米硬度与弹性模量分布

采用SEM,EDS等对融渗工艺制备的C/Ti比x分别为0.6,0.7,0.8和0.9的四种不同TiCx/Ni3Al复合材料进行了研究，证实Ti元素向金属相存在较强的扩散，而Ni和Al元素几乎没有向陶瓷相中扩散，扩散的结果形成了两相界面之间直接的原子结合，增加了复合材料相界面结合的强度和韧性，利用纳米压痕技术研究了复合材料相界面附近的纳米硬度H和弹性模量E，二者在相界面附近均呈连续梯度分布特征，并且TiC0.7/Ni3Al复合材料在界面处具有较高的纳米硬度值。     

Al、Ti掺杂对Mg2Ni合金相结构稳定性的影响及其微观机理

采用第一性原理赝势平面波方法,研究元素Al和Ti掺杂对Mg2Ni储氢合金相结构稳定性的影响及其微观机理.结果显示:在掺杂浓度x＝0～0.5范围内,所形成的Mg2Ni型Mg2-xMxNi(M＝Al,Ti)固溶体合金的相结构稳定性随Al掺杂浓度的增大而增强,随Ti掺杂浓度的增大而减弱,且Mg2-xMxNi(M＝Al,Ti)固溶体合金相对于立方结构的Mg3MNi2(M＝Al,Ti)化合物呈现热力学不稳定性,极易分解成由立方结构Mg3MNi2(M＝Al,Ti)和六方结构Mg2Ni组成的复合相,计算结果与实验结果吻合.电子结构分析表明,Al、Ti掺杂Mg2Ni储氢合金的相结构稳定性与体系在低能级区的成键电子数密切相关.     

代位合金元素对Fe3Al金属间化合物结构与塑性的影响

研究了Ｃｒ、Ｍｏ、Ｔｉ、Ｎｉ、Ｍｎ、Ｓｉ等代位合金元素对当量成分、ＤＯ３结构等轴晶Ｆｅ３Ａｌ合金真空拉伸性能、ＤＯ３转变温度Ｔｃ、ＤＯ３有序度、位错反相畴、位错组态等的影响，从合金元素原子在Ｆｅ３Ａｌ单胞亚点阵占位、原子解离能、反相畴界能等方面进行了初步探讨。结果表明，与Ｆｅ３Ａｌ相比，Ｃｒ的添加降低合金的Ｔｃ温度、提高真空拉伸延伸率，与ＣｒＡｌ原子对交互作用能、反相畴界能的降低有关；其它三元合金都表现高的Ｔｃ温度与低的塑性     

Electrochemical stability and surface analysis in evaluation fluoride effect on new bioalloy Ti7Al3V2Mo2Fe used in dentistry

The aim of this study is focused on the effect of fluoride concentration on the corrosion behavior of Ti7Al3V2Mo2Fe alloys uncoated/coated in artificial saliva. Ti7Al3V2Mo2Fe alloys were covered by chemical methods with hydroxyapatite to enhance the osteointegration of implants materials. The stability of Ti7Al3V2Mo2Fe alloys uncoated/coated in artificial saliva with/without fluoride ions was studied by electrochemical techniques (open circuit potential, cyclic voltammetry, and linear polarization). On the covered samples, dissolution test in simulated body fluids and wettability test were performed. Investigations regarding the sample surface modifications were made by atomic force microscopy and Fourier transform infrared spectroscopy. The results show that the corrosion resistance of Ti7Al3V2Mo2Fe in solution containing fluoride decreases in comparison with that in a solution not containing fluoride. Significant changes appear at a concentration larger than 0.05 M. The coating has a positive effect on corrosion resistance of metallic substrate in the fluoride presence acting as a semi‐mechanical barrier.     

Ni对V55Ti20．5Cr18．1Fe6．4合金吸放氢性能的影响

研究了用Ni元素取代一定量V对V55Ti20．5Cr18．1Fe6．4合金结构与性能的影响。结果表明，随Ni含量的增加，合金有效吸氢量先增大后减小，放氢压力增大，合金吸氢动力学性能也是先有所改善，而后又变差。添加0．1at％Ni有利于改善基体合金V55Ti20．5Cr18．1Fe6．4的吸放氢性能。用Ni元素取代V引起的晶胞体积的变化、放氢平台压力的升高以及杂质相的出现，是影响合金有效吸氢量和吸氢动力学性能的主要因素。     

氢对有序态Ni_3Fe合金脆性的影响(英文)

研究了有序态Ni3Fe合金在不同氢气压力中和在不同电流密度电解渗氢时合金的拉伸性能。结果表明：随着氢气压力或电流密度的增加,合金的延伸率先快速下降,随后逐渐趋于恒定;合金的氢脆因子与氢气压力或电流密度之间呈相同的依赖关系。有序态Ni3Fe合金在氢气中的脆化机制是催化反应生成的氢原子进入合金所致,合金的脆化程度与进入合金的氢原子数量有关。