Transient liquid phase bonding of DD5 superalloy using a designed interlayer: microstructure and mechanical properties

Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines.However,metallurgical defects during the manufacturing process and damage during harsh environmental service are inevitable challenges for turbine blades.Therefore,bonding techniques play a very important role in the manufacturing and repair of turbine blades.The transient liquid phase(TLP)bonding of DD5 Ni-based single crystal superalloy was performed using the designed H1 interlayer.A new third-generation Ni-based superalloy T1 powder was mixed with H1 powder as another interlayer to improve the mechanical properties of the bonded joints.The res-ults show that,such a designed H1 interlayer is beneficial to the improvement of shear strength of DD5 alloy bonded joints by adjusting the bonding temperature and the prolongation of holding time.The maximum shear strength at room temperature of the joint with H1 interlayer reached 681 MPa when bonded at 1260℃for 3 h.The addition of T1 powder can effectively reduce holding time or relatively lower bond-ing temperature,while maintaining relatively high shear strength.When 1 wt.%T1 powder was mixed into H1 interlayer,the maximum room temperature shear strength of the joint bonded at 1260℃reached 641 MPa,which could be obtained for only 1 h.Considering the bonding temperature and the efficiency,the acceptable process parameter of H1+5 wt.%T1 interlayer was 1240℃/2 h,and the room tem-perature shear strength reached 613 MPa.

Hybrid bonding of GaAs and Si wafers at low temperature by Ar plasma activation

High-quality bonding of 4-inch GaAs and Si is achieved using plasma-activated bonding technology.The influence of Ar plasma activation on surface morphology is discussed.When the annealing temperature is 300℃,the bonding strength reaches a maximum of 6.2 MPa.In addition,a thermal stress model for GaAs/Si wafers is established based on finite element analysis to obtain the distribution of equivalent stress and deformation variables at different temperatures.The shape varia-tion of the wafer is directly proportional to the annealing temperature.At an annealing temperature of 400℃,the maximum protrusion of 4 inches GaAs/Si wafers is 3.6 mm.The interface of GaAs/Si wafers is observed to be dense and defect-free using a transmission electron microscope.The characterization of interface elements by X-ray energy dispersion spectroscopy indi-cates that the elements at the interface undergo mutual diffusion,which is beneficial for improving the bonding strength of the interface.There is an amorphous transition layer with a thickness of about 5 nm at the bonding interface.The preparation of Si-based GaAs heterojunctions can enrich the types of materials required for the development of integrated circuits,improve the performance of materials and devices,and promote the development of microelectronics technology.

High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical use.The root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the electrode.Here,we present a novel synthesis of a composite combining expanded graphite and silicon nanoparticles.This composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering method.Notably,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.

Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy

The bonding interface characteristic and shear strength of diffusion bonded Ti-17 titanium alloy at different bonding time were investigated. The results show that the average size of voids decreases while the amount of voids decreases after increasing to the maximum value with the increasing bonding time. The irregular void with a scraggly edge tends to an ellipse void with smooth surface and then changes to a tiny void with round shape. The grains across bonding interface occur at bonding time of 60 min. The shear strength of bond increases with increasing bonding time, and the highest shear strength of bond is 887.4 MPa at 60 min. The contribution of plastic deformation on the void closure and the increase of shear strength is significant even though the action time of plastic deformation is short.

Influence of basicity and temperature on bonding phase strength,microstructure,and mineralogy of high-chromium vanadium–titanium magnetite

To develop a smelting process for the comprehensive utilization of high-chromium vanadium-titanium magnetite(HCVTM),the micro-sinter test was applied to investigate the influence of basicity and temperature on the HCVTM sinters.The bonding phase strength(BS) was tested via an electronic universal testing machine.The phase transformations of the HCVTM sinters were detected via X-ray diffraction(XRD),whereas the structure and mineralogy of the HCVTM sinters under different temperatures and basicities were detected via scanning electron microscopy in combination with energy-dispersive spectroscopy(SEM–EDS).Our results demonstrate that the BS of the HCVTM sinters exhibits a slightly increasing tendency with an increase in temperature when the basicity is 2.4 and within the range of 2.8–4.0.Many cracks,small size crystals,and dependent phase structures are generated by increasing the sinter basicity.The BS is lower than 4000 N when the basicity is 2.2 and 2.8.When the temperature is in the range of 1280–1300?C,the BS exceeds 4000 N with the basicity of 2.0,2.4,and 3.4–4.0.The pore size of the HCVTM sinters increases with the increase of the temperature.The perovskite decreases,whereas the silicate phase increases with basicity higher than 3.2.This study provides theoretical and technical foundations for the effective production of HCVTM sinters.

Strength prediction of multi-layered copper-based composites fabricated by accumulative roll bonding

This work aims to evaluate the feasibility of the fabrication of nanostructured Cu/Al/Ag multi-layered composites by accumulative roll bonding(ARB),and to analyze the tensile properties and electrical conductivity of the produced composites.A theoretical model using strengthening mechanisms and some structural parameters extracted from X-ray diffraction is also developed to predict the tensile strength of the composites.It was found that by progression of ARB,the experimental and calculated tensile strengths are enhanced,reach a maximum of about 450 and 510 MPa at the fifth cycle of ARB,respectively and then are reduced.The electrical conductivity decreased slightly by increasing the number of ARB cycles at initial ARB cycles,but the decrease was intensified at the final ARB cycles.In conclusion,the merit of ARB to fabricate this type of multi-layered nanocomposites and the accuracy of the developed model to predict tensile strength were realized.

Bonding strength of Invar/Cu clad strips fabricated by twin-roll casting process

Based on traditional twin-roll casting process,Invar/Cu clad strips were successfully fabricated by using solid Invar alloy strip and molten Cu under conditions of high temperature,high pressure and plastic deformation.A series of tests including tensile test,bending test,T-type peeling test and scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)measurements were carried out to analyze the mechanical properties of Invar/Cu clad strips and the micro-morphology of tensile fracture surfaces and bonding interfaces.The results indicate that no delamination phenomenon occurs during the compatible deformation of Invar/Cu in bending test and only one stress platform exists in the tensile stress-strain curve when the bonding strength is large.On the contrary,different mechanical properties of Invar and Cu lead to delamination phenomenon during the uniaxial tensile test,which determines that two stress platforms occur on the stress-strain curve of Invar/Cu clad strips when two elements experience necking.The average peeling strength can be increased from13.85to42.31N/mm after heat treatment at800℃for1h,and the observation of the Cu side at peeling interface shows that more Fe is adhered on the Cu side after the heat treatment.All above illustrate that heat treatment can improve the strength of the bonding interface of Invar/Cu clad strips.

Interfacial bonding strength of Al-Pb bearing alloy strips and hot dip aluminized steel sheets by hot rolling

Al Pb alloy strips and hot dip aluminized steel sheets were successfully bonded together by hot rolling, and the interfacial bonding strengths after rolling was evaluated by a new method. The bonding modes were studied by optical and scanning electron microscope and energy dispersive X ray analysis, and the effects of the thickness of the intermetallic layers and the Si content in hot dip aluminized layers on the interfacial bonding strength were also investigated respectively. It is found that the hot dipped steel and Al Pb alloy are bonded through blank interface bonding and block interface bonding, and the total bonding strength mainly depends on that of blank interfaces and the fraction of blank interfaces. There is a linear relationship between the total bonding strength F and the fraction of blank interfaces K b. The bonding strength varies with the Si content in the hot dipped aluminized layers on the surface of steel sheets, the fraction of blank interfaces and the rotation of the intermetallic blocks. [

Bonding strength of graded anti-corrosive coatings of fluoroethylenepropylene (FEP)/polyphenylene sulfide (PPS)

Fluororesin-based anti-corrosive coatings including graded FEP/PPS were prepared on carbon steel by melt powder coating, the bonding strength of all coating systems was determined by the pull-off test. It is found that the poor adhesion of fluororesin coatings to metallic substrates is improved obviously by the graded coating structure of FEP/PPS, and the bonding strength reaches up to 11.8 MPa for the five-layer system. Examination by electron probe microanalysis （EPMA） verifies that the distribution of main components is graded in the five-layer system, which is responsible for the enhancement of the interfacial bonding.

Bonding strength in carbon steel sandwich panels under condition of diffusion-rolling with small reduction

One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. Abonding assitant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rear metals were added to decrease the melting point and to obtain a better clouding and bigh plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3 min and the reduction rate is 9%.

Effect of ultrasonic power on wedge bonding strength and interface microstructure

During the aluminum wire wedge bonding, the ultrasonic power and bonding strength were obtained. Based on those data, the relationship between ultrasonic power and bonding strength was studied. The results show that: 1) ultrasonic power is affected by ultrasonic power ratio and other uncontrolled factors such as asymmetric substrate quality, unstable restriction on the interface between wedge tool and aluminum wire; 2) when ultrasonic power is less than 1.0 W, increasing ultrasonic power leads to increasing bonding strength and decreasing failure bonding; on the contrary, when ultrasonic power is greater than 1.6 W, increasing power leads to decreasing bonding strength and increasing failure bonding; 3) only when ultrasonic power is between 1.0 W and 1.6 W, can stable and high yield bonding be reached. Finally, the microstructure of bonding interface was observed, and a ring-shaped bond pattern is founded in the center and friction scrape besides the ring area.

Ceramic bonding and joint's strengthening through forming intermetallic compounds in situ

The transient liquid phase diffusion bonding of Si 3N 4 ceramics with Ti/Ni/Ti and Al/Ti/Al multiple interlayers was performed. The formation of intermetallic compounds in situ and their effects on the joints strengths were investigated. The Ti/Ni/Ti interlayers produce NiTi and Ni 3Ti layers with considerable room temperature ductility and high elevated temperature strength to strengthen the bonding zone metals and the joints. The joints with 142 MPa shear strength at room temperature and 88 MPa shear strength at 800 ℃ are achieved under appropriate parameters, respectively. Al/Ti/Al interlayers transform into a special bonding zone metal with a large amount of Al 3Ti particles and a small amount of Al based solid solution, and in this case, the joints are strengthened significantly. Their strengths at room temperature and 600 ℃ reach 90 MPa and 30 MPa, respectively.

MECHANICAL ANALYSIS AND NUMERICAL CALCULATION OF BONDING STRENGTH MEASUREMENT BY INTERFACIAL INDENTATION METHOD

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Effect of Curing Regime on Bonding Strength of EVA Modified Mortar to Tile

Ethylene-Vinyl Acetate （EVA） redispersible powder and latex were used to modify mortar. Three kinds of curing regimes： standard curing, high temperature curing and freeze-thaw circle curing were adopted to cure the bonded samples. Bonding strength of EVA modified mortar was tested at 28 days. The development of bonding strengths under all three curing regimes were discussed and compared. The experimental results show that bonding strength increases with the increase of EVA content in mortar. The curing regime used within 28 days is critical according to the bonding strengths values under three curing regimes for different ages. The reasons of that the EVA can improve the bonding strength were analyzed.

Microstructure and bonding strength of Ni-based alloy coating

A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.

Effects of intermixing process on bonding strength of IBED CrN coatings

The coating substrate bonding strengths under different intermixing processes were evaluated by scratch and spherical rolling contact fatigue methods. The results show that for low bombarding energy of N ions dynamic recoiling at 10 keV and 20 keV, the coating layers are of excellent bonding strengths. The bonding strength of CrN coating with 40 keV static recoiling is higher than that of low energy(20 keV). On the other hand, the bonding strength of coating with 40 keV dynamic recoiling is much lower than that of static recoiling at the same energy and even less than that of dynamic recoiling intermixings at 10 keV and 20 keV energy. The results of scratch and spherical rolling contact fatigue methods exhibit the same trend for each group of recoiling methods, yet the results of the scratch and fatigue tests for two groups do not agree with each other.

Atom Diffusion Behavior and Bonding Strength of Ag/Cu Composite Interface

The atom (Ag,Cu) diffusion behavior and the effect of technology on the interface of rolled Ag/Cu composite contact were investigated. The concentration of Ag and Cu atoms near the interface was determined with electron probe. The bonding strength of composite interface was tested and the fracture in tensile sample was observed by SEM. The results show that there was inter diffusion of Ag and Cu atoms on the interface, which formed compact layer with high bonding strength of 98 MPa. The practical application proved that the Ag/Cu composite interface is reliable.

The effect of zirconium coating on bonding strength of porcelain to titanium

The Zr coating was deposited on titanium surface using the magnetron sputtering technique. Effects of Zr coating on microstructure and mechanical properties of porcelain fired to titanium have been investigated. The results show that interdiffusion of elements occurs during porcelain firing, and the Zr coating can effectively protect titanium surface from excess oxidation. The strength of bond zone with Zr coating deposited for 1 hour reaches 29. 7 MPa, which has increased by 26.4% as compared with that of bond zone without coating （23.5 MPa）.

Study on interfacial structure and strength of Si_3N_4/Ti/Cu/Ti/Si_3N_4 PTLP bonding

Partial transient liquid-phase bonding （PTLP bonding） of Si3N4 ceramic with Ti/Cu/Ti multi-interlayer is performed with changing the thickness of Ti foil. The influence of Ti foil thickness on interface structure and joint strength was discussed. The joint interface structures are investigated by scanning electron microscope （SEM） and energy dispersion spectroscopy（EDS）. The results show that the maximum joint strength of 210 MPa is obtained at room temperature in the experiments. When joining temperature and time are not changed and the process of isothermal solidification is sufficient , interface structure, reaction layer thickness and isothermal solidification thickness change with the thickness of Ti foil.