Diffusion bonding of zirconia to silicon nitride using nickel interlayers

The possibilities of diffusion bonding of zirconia to silicon nitride using a nickel interlayer were studied by carrying out bonding experiments under various processing conditions. The process parameters considered were temperature, bonding pressure and interlayer thickness. The optimal process conditions were determined by evaluating the mechanical strength using shear strength testing. It was found that the bonding is optimal in the temperature range 1000–1100°C. The bond strength appears to be independent of the bonding pressure and interlayer thickness if threshold values are exceeded (bonding pressure >14 MPa, interlayer thickness >0.2 mm). At the Si3N4 Ni interface, Si3N4 decomposes, forming a solid solution of silicon in nickel. At the ZrO2–Ni interface, no reaction was observed. © 1998 Kluwer Academic Publishers     

Diffusion bonding of titanium alloy to micro-duplex stainless steel using a nickel alloy interlayer: Interface microstructure and strength properties

In the present study, diffusion bonding of titanium alloy and micro-duplex stainless steel with a nickel alloy interlayer was carried out in the temperature range of 800–950 °C for 45 min under the compressive stress of 4 MPa in a vacuum. The bond interfaces were characterised by scanning electron microscopy, electron probe microanalyzer and X-ray diffraction analysis. The layer wise Ni₃Ti, NiTi and NiTi₂ intermetallics were observed at the nickel alloy/titanium alloy interface and irregular shaped particles of Fe₂₂Mo₂₀Ni₄₅Ti₁₃ was observed in the Ni₃Ti intermetallic layer. At 950 °C processing temperature, black island of β-Ti phase has been observed in the NiTi₂ intermetallics. However, the stainless steel/nickel alloy interface indicates the free of intermetallics phase. Fracture surface observed that, failure takes place through the NiTi₂ phase at the NiA–TiA interface when bonding was processed up to 900 °C, however, failure takes place through NiTi₂ and β-Ti phase mixture for the diffusion joints processed at 950 °C. Joint strength was evaluated and maximum tensile strength of ∼560 MPa and shear strength of ∼415 MPa along with ∼8.3% ductility were obtained for the diffusion couple processed at 900 °C for 45 min.     

Diffusion bonding of AlCoCrFeNi_(2.1) eutectic high entropy alloy to TiAl alloy

High entropy alloys have special microstructure and remarkable properties.To explore their potential engineering application in high temperature structures,the microstructure evolution of bonding interface,the elemental diffusion behavior and mechanical property of the diffusion bonded joint between AlCoCrFeNi_(2.1)eutectic high entropy alloy(EHEA)and TiAl alloy were investigated.Four reaction layers(rodlike B2 phase,Al(Co,Ni)_2Ti,τ_3-Al_3NiTi_2+TiAl,τ_3-Al_3NiTi_2+TiAl+Ti_3Al)formed in the diffusion zone near FCC phase of EHEA,but three layers(Al(Co,Ni)_2Ti,τ_3-Al_3Ni Ti_2+Ti Al,τ_3-Al_3Ni Ti_2+Ti Al+Ti_3Al)formed near B2 phase.Al and Ni controlled the reaction diffusion of EHEA and TiAl alloy,coarsened the acicular precipitated B2 phase and turned Ti Al phase into Al(Co,Ni)_2Ti and τ_3-Al_3NiTi_2 phases.All these reaction layers grew in a parabolic manner as a function of bonding temperature.Rodlike B2 phase has the lowest growth activation energy of 125.2 kJ/mol,and the growth activation energy of τ_3-Al_3Ni Ti_2+TiAl layer near B2 phase is much lower than that near FCC phase.The penetration phenomenon and convex structure formed in the diffusion zone,which resulted in interlocking effect and enhanced the strength of resultant joints.The highest shear strength of 449 MPa was achieved at 950℃.And the brittle fracture generally initiated at the interface between Al(Co,Ni)_2Ti and τ_3-Al_3NiTi_2+TiAl layers.     

Diffusion bonding of an aluminium-lithium alloy (AA8090) using aluminium-copper alloy interlayers

Diffusion bonds have been produced between sheets of an Al-Li-Cu-Mg-Zr alloy using aluminium-4% copper vapour deposited metallic interlayers. Microstructural changes occurred both in the parent alloy and in the bond interface after diffusion bonding cycles and post-bonding heat treatments were analysed. Different metallographic techniques (light microscopy, scanning and transmission electron microscopy) have been used. Diffusion bonding trials were carried out using the same alloy (AA8090), both in non-superplastic (T6) and superplastic conditions. Differences in their behaviours in relation to diffusion bonding were observed.     

Mechanical properties and interfaces of zirconia/nickel in micro - and nanocomposites

The effect of processing parameters on the hardness and toughness of yttria-doped zirconia/nickel nanocomposites is reported. The experimental procedure consists in the deposition of nickel nanoparticles––previously obtained from nickel nitrate salts––on the surface of the zirconia powders. Slight changes in the proposed processing route (i.e. drying temperature of powders) gave rise to a noticeable decrease in the hardness (15–20%). However, no effect was observed on the toughness values in the studied composition range (0–30 vol% Ni). These results have been explained in terms of the nickel particle size distribution and agglomeration due to differences in the melting temperature of nickel nanoparticles, and because of epitaxial growth of nickel on the zirconia surface. For comparison purposes, samples obtained following a conventional wet-processing route starting from micrometric nickel and yttria-doped zirconia powders were prepared. In this case, the toughness is strongly dependent on the nickel fraction. This fact has been related to the weak bonding between metal and ceramic particles.     

Diffusion bonding of 410 stainless steel to copper using a nickel interlayer

In the present work, plates of stainless steel (grade 410) were joined to copper ones through a diffusion bonding process using a nickel interlayer at a temperature range of 800–950 °C. The bonding was performed through pressing the specimens under a 12-MPa compression load and a vacuum of 10^? 4 torr for 60 min. The results indicated the formation of distinct diffusion zones at both Cu/Ni and Ni/SS interfaces during the diffusion bonding process. The thickness of the reaction layer in both interfaces was increased by raising the processing temperature. The phase constitutions and their related microstructure at the Cu/Ni and Ni/SS diffusion bonding interfaces were studied using optical microscopy, scanning electron microscopy, X-ray diffraction and elemental analyses through energy dispersive spectrometry. The resulted penetration profiles were examined using a calibrated electron probe micro-analyzer. The diffusion transition regions near the Cu/Ni and Ni/SS interfaces consist of a complete solid solution zone and of various phases based on (Fe, Ni), (Fe, Cr, Ni) and (Fe, Cr) chemical systems, respectively. The diffusion-bonded joint processed at 900 °C showed the maximum shear strength of about 145 MPa. The maximum hardness was obtained at the SS–Ni interface with a value of about 432 HV.     

泡沫铝合金三明治结构结合界面及剪切性能的研究

提出了一种新的泡沫铝合金三明治结构的制备工艺--直接将铝板/混合粉末/铝板通过一次大压下量复合轧制,然后在炉中直接发泡成最终产品的制备工艺.实验成功的制备出铝面板的泡沫铝合金芯的三明治板.讨论了铝面板泡沫铝夹芯板轧制过程中以及发泡过程中界面的结合情况及界面结合机理.结果表明,轧制过程中界面结合属于机械结合,结合机制为薄膜理论;发泡过程中界面结合属于冶金结合,而铝面板与粉末体结合发泡后,界面处则只发生Al原子的互扩散,没有新相生成.剪切实验结果表明,预制坯的界面剪切强度较低,能够直接在界面处剥离开或者将板剥离开一半后将板拉断;而发泡后的泡沫铝夹芯板的界面结合力很强,剪切时断裂发生在芯材中或者铝面板上.     

Diffusion bonding of titanium alloy to stainless steel wire mesh

Abstract

The feasibility and appropriate processing parameters of diffusion bonding of titanium alloy to stainless steel wire mesh directly and with a nickel interlayer have been investigated. The microstructures of the diffusion bonded joints were observed by optical microscopy, scanning electron microscopy, X-ray diffraction, and electron probe microanalysis and the main factors affecting diffusion bonding were analysed. The maximum shear strengths of the joints were 72 and 148 MPa for direct bonding and indirect bonding using a nickel interlayer respectively. Atomic diffusion and migration between titanium and iron are effectively prevented by adding pure nickel as the interlayer metal, and a firm joint is obtained.     

Microstructure evolution upon annealing of accumulative roll bonding (ARB) 1100 Al sheet materials: evolution of interface microstructures

The microstructure evolution upon annealing of 1100 aluminum samples that were accumulative roll bonding (ARB) processed were studied with the use of transmission electron microscopy. It was found that the ultra-fine microstructure resulted from the ARB process was not stable. Specifically, a two-stage grain growth behavior was observed, in which a relatively slower rate of grain growth was followed by a more rapid grain growth rate at higher annealing temperature. The bonding interfaces that were unique to the roll bonding process were found to have a significant influence on the grain growth behavior when the grain size of the material was of similar dimension as the bonding interface separation. Discontinuous pockets consisting of smaller grains were found to have formed upon annealing. These pockets represented the remnants of the heavily deformed layer from wire brushing.     

Interface microstructures in diffusion bonding of titanium alloys to stainless and low alloy steels

Abstract

Commercial purity Ti and a Ti 6242 alloy have been diffusion bonded to an AISI 316L stainless steel and an AISI 4130 low alloy steel. The microstructures of the as processed products have been analysed using optical metallography, scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) techniques. The interdiffusion of the different elements through the interface has been determined using energy dispersive spectroscopy microanalysis in both a SEM and a STEM. For the combinations AISI 316L–commercially pure Ti and AISI 316L–Ti 6242 several regions surrounding the original interface have been observed. Starting from the 316L side, first a α phase is observed, followed by an Fe₂ Ti intermetallic, an FeTi intermetallic, and finally an Fe₂Ti₄O oxide just before the Ti and Ti 6242. Because the diffusion ofTi in Fe is faster than the diffusion of Fe in Ti, a Kirkendall effect is produced. In the AISI 4130–Ti 6242 combination a thin layer of TiC is observed at the interface, limiting the interdiffusion of elements.

MST/1746     

Diffusion bonding of Fe-28Al(Cr) alloy with low-carbon steel in vacuum

Fe-28Al(Cr) alloy and low-carbon steel were diffusion bonded in a vacuum of 10⁻⁴-10⁻⁵ Pa. The relationship of the bond parameters and shear strength at the interface was discussed. Microstructure characteristics and the reaction products at the interface were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The thickness of the diffusion reaction layer was measured with electron probe microanalysis (EPMA). The results indicated that controlling bonding temperature 1333 K for 3.6 ks, shear strength at the interface can be up to 112 MPa. Three kinds of reaction products were observed to have formed during the vacuum diffusion bonding, namely FeAl, Fe₃Al and α-Fe (Al) solid solution. The thickness (X) of the diffusion reaction layer increases with bonding time (t) according to a parabolic law X²=6.4×10³ exp(−104.1/RT)(t-t₀) (μm²).     

Mechanical fatigue behavior of chromium and nickel plain carbon steels

The influence of chemical composition on fatigue behavior and fatigue crack growth rates is variegated. Thus, chromium and nickel affect the fatigue limit but have no influence on the mean values of crack growth rates described by the Paris equations. The effect of carbon on the fatigue limit and the propagation of fatigue cracks is utterly different: It affects the exponentm on the right-hand side of the Paris equation, and the higher the content of carbon, the more pronounced its effect. Carbon also affects the dependencesm=f(Tr),m=f(HB),m=f(R), and logC=f(m) by changing the microstructure of the steel and, hence, the average fatigue crack growth rates. If the microstructure of a steel contains a ferrite phase or interlamellar ferrite in pearlite colonies, as observed in 0.2% and 0.4% carbon steels tempered at temperatures of 400°C and 600°C, then the mechanism of crack propagation is mainly connected with the formation of striations through the ferrite phase. In this case, the values ofm lie in the range of 2–4. This conclusion is made on the basis of data presented in [9, 10, 14, 15]. For a martensite or tempered martensite microstructure, as in 0.4% carbon steels as-quenched and tempered at 200°C, the predominant mode of fracture is intergranular separation and void coalescence, and the values ofm lie in the range of 4–6. For intermediate values of K, low-carbon steels (0.2%) are weakly sensitive to the mean stresses. This agrees with results obtained for other materials with a ductile mode of crack propagation. For 0.4% carbon steels tempered at 600°C, the exponentm increases from 3.5 to 5 asR increases from 0.1 to 0.85. Most likely, this is explained by an increased role for intergranular separation.Published in Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 1, pp. 62–67, January–February, 1995.     

Effect of transient liquid phase diffusion bonding on properties of ODS nickel alloy MA758

Abstract

An oxide dispersion strengthened (ODS) MA758 nickel alloy was bonded in the fine grain and recrystallised conditions using transient liquid phase diffusion bonding at 1100°C for various hold times. A microstructural study was undertaken to investigate the effect of post-bond heat treatments at 1360°C for 1 hand changes in parent metal grain size on developments of bond microstructure. Shear and fatigue tests were carried out to determine the mechanical integrity of the bonded samples. Results showed that shear and fatigue strengths of diffusion bonds made in the recrystallised condition were higher than those of bonds made in the fine grain condition. The results from oxidation tests performed at 1000°C show that the oxidation rate for samples bonded in the fine grain condition is higher than for those bonded in the recrystallised condition. However, localised oxidation of the joint region was not observed and this indicated that compositional homogeneity across the diffusion bonds had been attained.     

Mechanical properties and microstructures of machinable silicon carbide

Mechanical properties and microstructures of machinable silicon carbide, fabricated by pressureless sintering of silicon carbide fine powder with the aid of polysilastyrene, have been examined. Drastic changes in microstrucyure and in mechanical properties between specimens sintered at below 1773 K and at above 1873 K were observed. By sintering at above 1883 K the macinable silicon carbide had a good strength of more than 200 Mpa with high reliability, which was maintained beyond 1773 K. Polysilastyrene was converted in -phase silicon carbide and ribbon carbon in the pores. The (001) plane of carbon is parallel to the (111) planes of -phase silicon carbide.     

Investigation of microstructures and tensile properties of a Sn-Cu lead-free solder alloy

In recent years, the pollution of environment from lead (Pb) and Pb-containing compounds in microelectronic devices attracts more and more attentions in academia and industry, the lead-free solder alloys begin to replace the lead-based solders in packaging process of some devices and components. In this work, microstructures and mechanical properties of the lead-free solder alloy Sn99.3Cu0.7(Ni) are investigated. This paper will compare the mechanical properties of the lead-based with lead-free solder alloys (Sn99.3Cu0.7(Ni) and 63Sn37Pb). The tensile tests of lead-based and lead-free solder alloys (Sn99.3Cu0.7(Ni) and Sn63Pb37) were conducted at room and elevated temperature at constant strain rate; the relevant tensile properties of Sn99.3Cu0.7(Ni) and Sn63Pb37 were obtained. Specifically, the tensile strength of this lead-free solder- Sn99.3Cu0.7(Ni) in 25^∘C, 50^∘C, 75^∘C, 100^∘C, 125^∘C was investigated; and it was found that tensile strength of the lead-free solder decreased with the increasing test temperature at constant strain rate, showing strong temperature dependence. The lead-free solder alloy Sn99.3Cu0.7(Ni) was found to have favorable mechanical properties and it may be able to replace the lead-based solder alloy such as Sn63Pb37 in the packaging processes in microelectronic industry.