Ti-Ni-Cu三元扩散偶的界面研究

采用"铆钉法"制备了界面为曲面的Ti-Ni-Cu三元扩散偶,使用光镜和扫描电镜,结合电子探针微区元素分析技术,对扩散反应进行了分析.结果表明,Ti-Ni-Cu三元扩散偶在973 K反应200h,共生成了10个扩散溶解反应层,其中包括两个Ti-Ni二元金属间化合物(Ti2Ni,TiNi);3个Ti-Cu二元金属间化合物(TiCu,Ti3Cu4和TiCu4);5个Ti-Ni-Cu三元金属间化合物(TiNi2Cu,CuNi29Ti10,Cu3NiTi8,Cu12NiTi7,Ti50Ni32Cu18).     

热处理对机械合金化Ni/Ti冷喷涂层金属间化合物形成的影响

选择了三种球磨时间制备的Ni/Ti机械合金化粉末,通过冷喷涂制备了不同结构的Ni/Ti涂层.涂层组织结构采用扫描电镜(SEM)和X射线衍射(XRD)进行了表征分析.试验发现,随着粉末球磨时间的增加,热处理后的冷喷涂合金转变为金属间化合物的温度下降,涂层的组成相由Ni3Ti,B2-NiTi和Ti2Ni逐渐变成Ni3Ti和Ti2Ni;随着热处理温度的增加,涂层组织中不同成分的金属间化合物的相对量会发生一定改变.结果表明,热处理过程中形成的B2-NiTi金属间化合物在冷却时表现出较高的稳定性.     

扩散连接接头金属间化合物新相的形成机理

扩散连接接头中界面区脆性金属间化合物相的出现往往会造成接头性能的恶化,因此研究并建立接头界面区金属间化合物相的生成和成长行为的数学模型对扩散连接过程有非常重要的理论及现实意义。本文根据扩散理论,指出界面处生成相的动力学驱动力限决于扩散偶中组元自身的特性,生成机的组元及比例应按原子扩散通量比优先生成,本文从动力学及热力学角度出发,提出了多组元扩散偶界面处的金属间化合物生成相原则：通量-能量原则;并以钛/镍/钢扩散接接头为例,证明钛/镍界面处金属间化合物相的生成规律为Ni/TiNi3/TiNi/Ti2Ni/Ti。提出,通量-能量能力相当的两种或多种金属间化合物有可能同时形核篚,接头界面处会形成混合的金属间化合物。     

Ni/Sn固液扩散偶相界面的实验研究

采用"坩埚法"制备了曲面的Ni/Sn同液扩散偶,将扩散偶置于SK2管式电阻炉中在不同的工艺条件下进行热处理,利用光学显微镜和电子探针微区分析技术对相界面的变化和扩散层的成分进行观察和分析.结果表明,Ni/Sn扩散溶解层的厚度和层数随温度的升高和时间的延长而增加,生成金属间化合物的顺序依次为Ni3Sn4、Ni3Sn、Ni3Sn2.     

Ni+Cu为中间层的TC4与ZQSn10-10的扩散连接试验分析

对钛合金TC4与铜合金ZQSn10-10异种金属扩散连接进行了试验研究.采用Ni Cu中间层时,其最佳工艺参数为连接温度850 ℃,连接时间20 min,连接比压力10 MPa,抗拉强度达到155.8 MPa.在TC4/Ni界面上,形成了成分逐渐变化的互扩散层.经微区成分分析可知,连接温度为800 ℃时,界面主要为Ni3Ti;850 ℃时,界面主要为Ni3Ti及NiTi;880 ℃时,界面主要为NiTi2,Ni3Ti及NiTi.通过EDS和XRD分析,接头强度主要取决于镍钛金属间化合物的种类及厚度.     

原位自生TiAl3增强Al基复合材料的组织结构及形成机理研究

采用冷喷涂技术沉积Ti-80Al（wt.%）复合涂层,通过热处理获得了原位自生TiAl3金属间化合物颗粒增强Al基复合材料涂层。采用SEM、EDS和XRD等分析了冷喷涂Ti/Al复合涂层在不同热处理温度下的组织结构演变规律及Ti、Al粒子间原位扩散反应过程,并对TiAl3金属间化合物的形成机理进行了探讨。结果表明,冷喷涂Ti/Al复合涂层组织致密,其相结构与喷涂粉末完全相同,450℃热处理后涂层局部区域发生Ti、Al间的固态扩散反应,并在Ti、Al粒子界面原位形成TiAl3金属间化合物,随着热处理温度升高,TiAl3金属间化合物的含量显著增加,600℃热处理后,Ti/Al复合涂层中的Ti粒子全部转变为TiAl3金属间化合物,获得原位自生TiAl3颗粒增强的Al基复合材料.     

6061铝基体上镍涂层热处理过程中Ni-Al金属间化合物的形成机理(英文)

采用电沉积方法在Al基体上沉积Ni制备Ni-Al扩散偶,并研究扩散偶中Al3Ni和Al3Ni2的形成机理和生长动力学。在6061铝基体上采用直流电沉积方法制备20μm厚的Ni涂层。然后在Ar气气氛下,样品在450,500和550°C下热处理不同时间。采用扫描电子显微镜、能谱仪和X射线衍射仪对金属间化合物进行表征。结果表明,Ni-Al金属间化合物的形成可分为两个重要步骤。首先,金属间化合物在不同位置侧面生长,形成连续金属间化合物层;其次,连续金属间化合物层在垂直于界面方向继续生长。随着金属间化合物厚度的增长,Al3Ni和Al3Ni2等反应产物将与基体发生分离。Al是Al3Ni生长的主要扩散元素,而Ni是Al3Ni2生长的主要扩散元素。Al3Ni和Al3Ni2相的生长动力学遵循抛物线方程。     

原位自生TiAl_3增强Al基复合材料的组织结构及形成机理

采用冷喷涂技术沉积Ti-80Al(质量分数,%)复合涂层,通过热处理获得了原位自生TiAl_3金属间化合物颗粒增强Al基复合材料涂层。采用SEM、EDS和XRD等分析了冷喷涂Ti/Al复合涂层在不同热处理温度下的组织结构演变规律及Ti、Al粒子间原位扩散反应过程,并对TiAl_3金属间化合物的形成机理进行了探讨。结果表明,冷喷涂Ti/Al复合涂层组织致密,其相结构与喷涂粉末完全相同,450℃热处理后涂层局部区域发生Ti、Al间的固态扩散反应,并在Ti、Al粒子界面原位形成TiAl_3金属间化合物,随着热处理温度升高,TiAl_3金属间化合物的含量显著增加,600℃热处理后,Ti/Al复合涂层中的Ti粒子全部转变为TiAl_3金属间化合物,获得原位自生TiAl_3颗粒增强的Al基复合材料。     

钛合金镀后热处理对镀层结合力的影响

主要研究了TC4钛合金镀后热处理对镀镍或铜／层结合力的影响。结果表明,热处理后镀层与基体之间的界面形成以固溶体或金属间化合物为主的扩散层,采用XRD分析扩散热处理后镀层与基体之间的界面表明,扩散层中存在Ni3Ti,NiTi,NiTi2等金属间化合物;镀层结合力的提高与热处理后所形成扩散层的厚度无直接关系,而认为其主要取决于是否有利于镀层与基体之间金属键的形成。当扩散层中的固溶体或金属间化合物足以破坏镀层与其体之间存在的氧化膜等非金属膜层的完整性,而镀层与基体之间的微观间隙不因热处理而增大时,则能促进镀层与基体之间金属键的形成,从而提高镀层的结合力。     

Cu与NbTi之间扩散反应的研究

采用电子探针微分析术研究了机械复合和冶金复合两种界面状态的Nb-Ti/Cu复合超导线,以及Nb-Ti/Cu,Ti/Cu和Nb/Cu偶的扩散反应过程.结果表明,原始组件的界面状态对Nb-Ti/Cu间金属间化合物的生成有明显的影响.机械复合组件较冶金复合组件能承受更高的热处理温度而不致生成金属间化合物.Ti与Cu之间反应生成化合物的次序与形态及NbTi与Cu之间不同.Ti/Cu间生成化合物的厚度y与时间t关系遵循y~(1.5-t)的规律.     

Isothermal section at 927℃ of Cr-Ni-Ti system

The isothermal section at 927℃ of the Cr-Ni-Ti system was established using a high-efficiency diffusion couple approach, supplemented with eight equilibrated alloys. The alloy compositions were selected on the basis of the experimental results from the diffusion couple. Both the diffusion couple specimens and the alloys were examined by means of optical microscopy, scanning electron microscopy, and electron probe microanalysis. No ternary compound is found at 927℃. The following five three-phase equilibria are well determined： TiNi3＋（Cr）＋（Ni）, TiNia＋（Cr）＋TiNi, TiNi＋（Cr）＋Cr2Ti, Ti2Ni＋Cr2Ti＋TiNi and Ti2Ni＋Cr2Ti＋（Ti）. The solubilities of Cr in NiTi2, NiTi, and Ni3Ti are determined to be 7.5%, 14.5% and 11.4% （molar percent）, respectively, α-Cr2Ti and β-Cr2Ti dissolve about 9.2% and 13.9% Ni （molar percent）, respectively.     

Microstructure and Adhesion Strength of Ni<Subscript>3</Subscript>Ti Coating Prepared by Mechanical Alloying and HVOF

In the present work we report the development of Ni₃Ti intermetallic compound by high energy ball milling of Ni and Ti powders. The ball milled powders were taken at various intervals (4, 6, 8, 10, and 11 h) to analyze the formation of Ni _x Ti _x intermetallic compounds. The ball milled powders were analyzed using scanning electron microscopy and X-ray diffraction. The layered shaped powder particles of Ni₃Ti phase were formed after 11 h of ball milling, which was confirmed by X-ray peaks. Further High-Velocity Oxy-Fuel (HVOF) process was used to coat Ni₃Ti and Ni₃Ti + (Cr₃C₂ + 20NiCr) on MDN 420 steel. Both the coated materials displayed excellent cohesion with minimal porosity less than 2%. The tensile adhesion strength test was carried out on these coatings to check the bond strength. Out of the two the Ni₃Ti coating showed excellent bond strength of 41.04 MPa compared to that of Ni₃Ti + (Cr₃C₂ + 20NiCr) coating.     

Kinetic study of non-isothermal crystallization in Al80Fe10Ti5Ni5 metallic glass

This study investigated the crystallization behavior of a kinetically metastable Al₈₀Fe₁₀Ti₅Ni₅ amorphous phase. The Al₈₀Fe₁₀Ti₅Ni₅ amorphous phase was synthesized via the mechanical alloying of elemental powders of Al, Fe, Ti, and Ni. The microstructures and crystallization kinetics of the as-milled and annealed powders were characterized using X-ray diffraction, transition electron microscopy, and non-isothermal differential thermal analysis techniques. The results demonstrated that an Al₈₀Fe₁₀Ti₅Ni₅ amorphous phase was obtained after 40 h of ball milling. The produced amorphous phase exhibited one-stage crystallization on heating, i.e., the amorphous phase transforms into nanocrystalline Al₁₃(Fe,Ni)₄ (40 nm) and Al₃Ti (10 nm) intermetallic phases. The activation energy for the crystallization of the alloy evaluated from the Kissinger equation was approximately 538±5 kJ/mol using the peak temperature of the exothermic reaction. The Avrami exponent or reaction order n indicates that the nucleation rate decreases with time and the crystallization is governed by a three-dimensional diffusion-controlled growth. These results provide new opportunities for structure control through innovative alloy design and processing techniques.     

Annealing effects on the intermetallic compound formation of cold sprayed Ni,Al coatings

The annealing of Ni and Al coatings under various conditions on substrates fabricated by a cold gas dynamic spray process (CDSP) were investigated. The powder particles were accelerated through a standard De Laval-type nozzle with air used as the main carrying gas. The coatings were annealed at 450–550 °C in either argon or air atmospheres for 4 h. In the case of Ni coatings during annealing both in argon and air atmospheres, intermetallic compound layers such as Al₃Ni and Al₃Ni₂ were observed at the interfaces between the Ni coating and Al substrate. Also, the intermetallic layer formation of Al₃Ni and Al₃Ni₂ at the interfaces depended on the solid-state diffusion and the annealing temperature. The intermetallic compound AlNi was obtained at the interface of Al coating on a Ni substrate by low-temperature annealing under the melting temperature.     

Hydrogenation properties of shape memory Ti(Ni,Pd) compounds

The effect of Pd substitution on the crystal structure and hydrogenation properties of TiNi compound has been investigated. Ti(Ni,Pd) are pseudo-binary compounds. The unit-cell volumes of B2 (Austenite) and B19 (Martensite) structures linearly increase with Pd substitution in Ti_1.04Ni_0.96?xPd_x samples. The hydrogenation properties of Pd-substituting Ti(Ni,Pd) compounds are not affected by the crystal structure of the parent compounds. For all samples, hydrogen absorption occurs without showing any clear plateau pressure in Pressure-Composition-Isotherm (PCI) curves. All hydrided samples crystallise in the tetragonal I 4/mmm space group. At 6 MPa of hydrogen pressure and T = 423 K, the hydrogenation capacity of Ti(Ni,Pd) compounds reaches 1.52 hydrogen atoms per formula unit (H/f.u.) for x = 0.1 and then gradually decreases with Pd content down to 0.93 H/f.u. for x = 0.5. Ti_1.04Ni_0.86Pd_0.10 sample yields a discharge capacity of 148 mAh/g at C/5 regime when used as negative electrode in Ni-MH battery. The hydrogenation properties of Pd-substituting Ti(Ni,Pd) compounds are discussed in detail by comparison with previous studies on Zr substituting, (Ti,Zr)Ni compounds.     

Investigating the influence of Ti powder purity on phase evolution during NiTi sintering using in-situ neutron diffraction

The influence of Ti powder purity on phase evolution during the reactive sintering of elemental Ni and Ti powders to form NiTi was studied using differential scanning calorimetry (DSC) and in-situ neutron diffraction. Reaction between the Ni and Ti is not significant until 600 °C. From 600 to 700 °C, Ti₂Ni forms in mixtures made from high (HP) and low purity (LP) Ti powder. The Ni₃Ti phase also grows in this temperature range in the LP mixture. The most significant phase evolution takes place between 700 and 920 °C. The α to β phase transformation in (Ti) begins at the eutectoid temperature (765 °C) and ends at 820 °C. The highest growth rates for all three intermetallic phases, including NiTi, and the decay rate of the elemental Ni occur in this temperature range. At approximately 1000 °C, all reactants are consumed and homogenization occurs, with NiTi continuing to grow at the expense of the other intermetallic phases. The Ti rich intermetallic phase persists above its melting point, due to the formation of a solid-solution with oxygen (i.e. Ti₂Ni(O)). From 1100 to 1200 °C, the microstructure becomes a stable mixture of NiTi with a small fraction of Ti₂Ni(O). The phase evolution is similar in the LP and HP mixtures. However, the rate of reaction is higher in the LP mixture due to the influence of impurities (O, Fe and Ni) on the diffusivities in the many phases involved.     

Dissolution and interfacial reactions of thin-film Ti/Ni/Ag metallizations in solder joints

The dissolution and interfacial reactions involving thin-film Ti/Ni/Ag metallizations on two semiconductor devices, diode and metal-oxide-semiconductor field-effect transistor (MOSFET), a Sn–3.0Ag–0.7Cu solder, and a Au-layer on the substrates are studied. To simulate the dissolution kinetics of the Ag-layer in liquid solder during the reflow process, the computational thermodynamics (Thermo-Calc) and kinetics (DICTRA: DIffusion Controlled TRAnsformations) tools are employed in conjunction with the assessed thermochemical and mobility data. The simulated results are found to be consistent with the observed as-reflowed microstructures and the measured Ag contents in the solder. In the as-reflowed joints two different intermetallic compounds (IMC) are found near the diode/solder interface. Both are in the form of particles of different morphologies, not a continuous layer, and are referred to as IMC-I and IMC-II. The former corresponds to Ni₃Sn₄ with Cu atoms residing in the Ni sublattice. It is uncertain whether IMC-II is Cu₆Sn₅ phase with Ni atoms residing in the Cu sublattice or a Cu–Ni–Sn ternary phase. Near the as-reflowed MOSFET/solder interface, both particles and a skeleton-like layer of Ni₃Sn₄ are observed. The primary microstructural dynamics during solid state aging are the coarsening of IMC particles and the reactions involving the unconsumed (after reflow) Ni- and the Ti-layer with Sn and Au. While the reaction with the Ni-layer yields only Ni₃Sn₄ intermetallic, the reaction involving the Ti-layer suggests the formation of Ti–Sn and Au–Sn–Ti intermetallics. The latter is due to the diffusion of Au from the substrate side to the die side. It is postulated that the kinetics of Au–Sn–Ti layer is primarily governed by the diffusion of Au through the Ni₃Sn₄ layer by a grain boundary mechanism.