Nb Interlayer Research Articles

Coupling influence of laser-Nb interlayer on microstructure and performance of Ti/Al joint

Laser fusion welding of TC4 titanium (Ti) alloy and aviation 7075 aluminum (Al) alloy was conducted with the assistance of a niobium (Nb) interlayer. The effect of laser heat input and the alloying effect of Nb on the interfacial layer was analyzed. The study also investigated the coupling influence of the laser-Nb interlayer on the microstructure and performance of the Ti/Al joint. By utilizing a 0.1 mm-thick Nb interlayer and a welding velocity of 1800 mm/min, the results reveal an initial increase in tensile-shear force followed by a decline with the increase of laser power. The tensile-shear force reached a peak of 1663 N at 1.2 kW, representing a 36.76 % improvement over the 1 kW levels. Under appropriate laser power, the enhancement in joint performance is dominated by the controlled heat input and the effective Nb-alloying effect, which reduce the thickness and brittleness of the interfacial intermetallic layer, respectively. However, metallurgical regulation of Nb will be restricted by the insufficient Nb melting amount resulting from the low laser power, leading to a decrease in joint properties. Excessive laser power can lead to the formation of hot cracks and an excessive amount of Ti-Al intermetallic compounds, which can decrease the Nb content, thereby restricting the metallurgical regulation of Nb and the overall joint performance.

Effect of Nb interlayer thickness on interfacial products and mechanical properties of Ti–6Al–4V/EH690 steel clad plate by vacuum hot rolling

The high content of alloying elements in Ti alloys and high-strength steels, combined with the requirement for quenching and tempering heat treatment during the fabrication process of the clad plate, leads to complex interfacial products and poor bonding properties. An Nb interlayer was introduced to enhance the mechanical properties of Ti alloy/steel clad plates. This work investigated the effect of Nb interlayers with initial thicknesses of 10, 25, and 50 μm on the evolution of interfacial products and bonding properties. The results indicated that when the interlayer was thin (10 μm thick), the diffusion of Ti, Fe, and C in the matrix and clad materials could not be completely inhibited due to the uneven distribution of the Nb interlayer at the interface. TiC, NbC, Nb2C, and Fe2Nb were detected at the Nb/steel interface. With the thickness of the interlayer increased (reaching 25 μm or 50 μm), the influence of uneven deformation on the interlayer was weakened, and the Nb/steel interface was composed of Nb2C and Fe2Nb. The tensile shear test indicated that the fracture occurred at the Nb/steel interface and the Nb interlayer. The plasticity of the micrometer Nb interlayer decreased with the increase in interlayer thickness. Therefore, more cracks and brittle fracture characteristics were observed in the fracture surface of the 50 μm thick Nb interlayer sample. The clad interface with a 25 μm thick Nb interlayer exhibited the highest interfacial shear strength of 295 MPa due to the few intermetallic compounds (IMCs) at the Nb/Steel interface and the excellent plasticity of the Nb interlayer.

Microstructural evolution and mechanical properties of Zr-4 alloy joints diffusion bonded with Nb interlayer

To obtain a robust diffusion-bonded joint at a relatively low temperature, Nb foil was applied as an interlayer to the diffusion bonding of Zr-4 alloy, and a wide process parameter involving the bonding temperature of 720–820 °C and holding time of 30–120 min was investigated to reveal the evolution of interfacial structure and mechanical properties of the joints. The β-(Zr, Nb) and Widmanstädter microstructure formed at the interface induced by the eutectoid transformation of the diffused Zr and Nb at the bonding temperatures over 740 °C. The phase structure and the thickness of β-(Zr, Nb) layer were not considerably influenced by the increase in diffusion parameters while the Widmanstädter zone thickened significantly. Moreover, the tensile strength and elongation of the resultant joints could be stabilized above 433 MPa and 7.8%, respectively, when the bonding temperature exceeded 760 °C with a holding time of 30 min. By extending the holding time to 60 min at 760 °C, the tensile strength and elongation could reach 454 MPa and 12.6%, respectively, comparable to those obtained at an elevated temperature of 820 °C for 30 min. Additionally, the samples fractured at the diffusion layer were characterized by the in-situ tensile test under the scanning electron microscope, and it was discovered that the crack initiation and propagation process occurred mainly between the β-(Zr, Nb) and Widmanstädter diffusion zone.

Multi-material wire arc additive manufacturing of a bio-inspired heterogeneous layered NiTi/Nb/Ti6Al4V structure: Microstructural evolutions and mechanical properties

Obtaining a reliable NiTi–Ti6Al4V(TC4) heterogeneous alloy component exhibiting excellent strength and elasticity via integrating distinct material benefits can provide design flexibility in multifunctional device fabrication. However, the fabrication of this materials couple is challenging due to the development of excessive Ti2Ni intermetallic compound. Inspired by the bioheterogeneous layered structure, Nb interlayer was applied for the wire arc additive manufacturing (WAAM) of NiTi and TC4 to restrict the mixing of alloying elements on both sides. However, the strength of NiTi–Nb-TC4 alloy component was limited by pure Nb characteristics when the NiTi and TC4 was completely separated by the unmolten Nb interlayer. In this work, the tensile strength perpendicular to the interface of NiTi–Nb-TC4 alloy component was enhanced to introduce appropriate amount Ni and Ti in Nb interlayer by adjusting the composite WAAM process at the expense of Ti2Ni. Microstructure evolution, composition change and mechanical properties of composite WAAM NiTi–Nb-TC4 alloy component were investigated. It was shown that the compression strength and fracture strain perpendicular to the interface of WAAM NiTi–Nb-TC4 sample was 1549.0 ± 17 MPa and 22.3 ± 8 %, and the compressive strength can reach 63.6 % and 94.5 % of WAAM NiTi alloy and TC4 alloy, respectively. The composite WAAM NiTi–Nb-TC4 sample maintained 65.3 % recovery rate after ten compression cycles, which confirmed that partial superelasticity was maintained in the WAAM NiTi–Nb-TC4 multilayer structure. This fact further proved that WAAM can be successfully applied to deposit shape memory/superelastic alloys. The use of the Nb interlayer enhanced the tensile strength perpendicular to the interface to 460.7 ± 16 MPa. The ultimate tensile strength perpendicular to the interface of composite WAAM NiTi–Nb-TC4 sample can reach 72.0 % and 60.0 % of WAAM NiTi alloy and TC4 alloy, respectively. The formation of NiTi, TiNb and β-Nb phases in Nb interlayer and the network distribution of Ti2Ni and TiNb phases explained the improved mechanical performance of the composite WAAM NiTi–Nb-TC4 alloy component.

Joining of graphite to Mo using Ti/Cu and Ti/Cu/Nb/Ti/Cu foils

Graphite/Mo joining has been carried out using Ti/Cu or Ti/Cu/Nb/Ti/Cu foils. The joining region in the joint using Ti/Cu foils is mainly composed of Ti3Cu4 and TiCu. The joining region using Ti/Cu/Nb/Ti/Cu foils contains a joining zone I, an Nb interlayer and a joining zone II. Both the joining zones I and II are made up of Ti3Cu4 and TiCu. The Nb foil diffuses and dissolves into the liquid fillers during the bonding. The joint using Ti/Cu/Nb/Ti/Cu foils shows higher shear strength than that using Ti/Cu foils, implying the contribution of Nb foil to the joint stress relief and to the joint strength promotion.

Effect of Nb interlayer on microstructure and property of Ti-6Al-4V/690 MPa grade steel clad plate by vacuum rolling

Ti alloy clad plate is of great interest for marine and petrochemical industry applications. However, high interfacial bonding is hardly obtained in the Ti alloy clad plate due to the brittle intermetallic compounds (IMCs) forming at the interface. In this study, a Ti-6Al-4V alloy/EH690 steel clad plate was fabricated by vacuum rolling and subsequently tempered to control the mechanical property of the steel substrate. The tempered sorbite appeared in the EH690 steel after quenching and tempering (QT). A decarburized zone, Fe2Ti + TiC mixed phases layer, and β-Ti layer were formed at the interface between steel and Ti. The brittle IMCs with high lattice mismatch resulted in a low interfacial strength of 108 MPa. To improve bonding strength, Nb was inserted between Ti and steel as an interlayer, which effectively inhibited the inter-diffusion of Ti, Fe, and C without brittle TiC or Fe-Ti IMCs. A (Ti, Nb) solid solution layer with high plasticity was present at the Nb/Ti interface. Fe2Nb and Fe7Nb6 phases were detected at the steel/Nb interface, exhibiting less brittleness and hardness compared to Fe-Ti IMCs. The interfacial shear strength was up to 265 MPa after adding the Nb interlayer, showing a mixed fracture mode of brittleness and ductility.

Revealing microstructural evolution and mechanical properties of resistance spot welded NiTi-stainless steel with Ni or Nb interlayer

Dissimilar welding of NiTi and stainless steel (SS) for multifunctional device fabrication is challenging due to the brittle nature of intermetallic compounds (IMCs) that are formed in the weld zone. In this work, Ni and Nb interlayers were applied for the resistance spot welding (RSW) of NiTi and SS to replace the harmful Fe2Ti phase and to restrict the mixing of dissimilar molten metals, respectively. Microstructural evolution and mechanical properties of the joints were investigated. It was shown that a conventional weld nugget was created in the absence of any interlayer in the welded joint suffering from traversed cracks due to the formation of brittle IMCs network in the fusion zone (FZ). By the addition of Ni from the interlayer, Fe2Ti dominated weld nugget was efficaciously replaced by Ni3Ti phase; however, the presence of the large pore and cracks reduced the effective joining area. The use of a Nb interlayer resulted in a fundamentally different joint, in which FZs at NiTi and SS sides separated by the unmolten Nb would suppress the mixing of dissimilar molten metals. Nb-containing eutectic structures with low brittleness formed at the interfaces, contributing to the enhancement of joint strength (increased by 38% on fracture load and 460% on energy absorption). A high-melting-point interlayer showed great potential to realize a reliable and high-performing RSWed NiTi-SS joint.

Effect of interlayer and deposition temperature on the hydrogen storage properties of amorphous Mg-based thin films

In this work, the effect of different interlayers (including Mo, Nb, and Ti) and deposition temperatures (including 25 °C, 75 °C, 150 °C and 200 °C) on the hydrogen storage performance of MgNi amorphous alloy films are studied. On the one hand, the MgNi amorphous alloy films remain undestroyed after hydrogen absorption and desorption cycles with the help of Mo, Nb and Ti interlayers. However, the onset desorption temperature and peak desorption temperature of the MgNi amorphous alloy films are almost unchanged after inserting the interlayers. On the other hand, as the deposition temperature increases from 25 °C to 200 °C, there are nanocrystalline Mg2Ni and Mg phases formed in the amorphous MgNi alloy matrix. The crystalline-amorphous structure provides abundant nucleation sites for hydride formation, and accelerate the diffusion and dissociation of hydrogen.

Strengthening mechanism in the dissimilar CpTi/Inconel 718 joints obtained through diffusion bonding.

The lap joints of the CpTi/Inconel-718 was obtained by Diffusion bonding (DB) at 1020 °C for 1.5 h. Microstructure and chemical composition of the lap joints were examined using polarizing Microscope, Scanning Electron Microscope(SEM) and X-Ray Diffraction(XRD). The region of the CpTi in the vicinity of interface was transformed into β-Ti and after to that was a region observed as α-Ti Widmanstatten needles in a matrix of β-Ti. This transformation of CpTi into β-structure in the vicinity of the interface was attributed to the diffusion of β-stabilizers from the Inconel side of the joint. The average shear strength of the DB CpTi/Inconel-718 joints was measured to be 223 MPa which was greater than the conventional Pulsed TIG (P-TIG) weldment of CpTi/Inconel-718 obtained using the V and Nb interlayers. This was attributed to the stabilization of β-Ti as well as confinement of IMCs to a thinner region in the DB CpTi/Inconel-718 joints.

Benchmarking the performance of lithiated metal oxide interlayers at the LiCoO2|LLZO interface

Lithiated Nb, Al, or Ti metal oxide interlayers improve the LiCoO2/LLZO interface, whereby the Li–Nb–O interlayer exhibits the highest performance.

Laser Additive Manufacturing of TC4/AlSi12 Bimetallic Structure via Nb Interlayer.

The TC4/AlSi12 bimetallic structures (BS) with Nb interlayer transition were fabricated by laser additive manufacturing (LAM). The results showed that the TC4/AlSi12 BS with Nb interlayer prepared with optimized process parameters can be divided into three regions (the TC4 region, Nb region and the AlSi12 region) and two interfaces (the TC4/Nb interface and the Nb/AlSi12 interface). The high melting point (Ti, Nb) solid solution formed in the Nb region acted as a diffusion barrier between the TC4 alloy and the AlSi12 alloy, thereby effectively inhibiting the formation of Ti-Al intermetallic compounds (IMCs). With the decrease of the laser output power for AlSi12 deposition, the NbAl3 IMC changed from layered to dispersed distribution, while γ-TiAl and Ti5Si3 IMC disappeared, thus significantly reducing the crack susceptibility of the BS deposited layer. The tensile strength of TC4/AlSi12 BS with Nb interlayer was about 128MPa, and the fracture was located near the Nb/AlSi12 interface.

Direct energy deposition of Cu–Nb functionally graded layers for dissimilar joining titanium alloys and steels

The heterogeneous compounds of titanium and iron steel are of wide interest in additive manufacturing. To prevent the formation of brittle intermetallic compounds, a layer of Nb and Cu was used. The use of the Nb and Cu interlayer successfully prevents the mixing of Ti and Fe, thus avoiding the formation of FexTiy brittle phases. In the Ti–Nb–(Nb + Cu–10Al) transition interlayer, it was possible to achieve the interlayer without the formation of brittle phases. The static tensile strength of the Grade1/316 L compounds with Nb–(Nb + Cu–10Al) interlayer is 335.5 MPa, the compounds exhibit ductile–brittle fracture.

Diffusion bonding of Zr-2.5Nb zirconium alloy and 304L stainless steel with Nb/Ni hybrid interlayer

• Nb/Ni hybrid interlayer was applied to join 304L SS and Zr-2.5Nb Zr alloy. • The diffusion area has significantly stratified structure. • Ni 3 Nb IMCs occurred in the Nb/Ni interface with high hardness. Diffusion bonding of Zr-2.5Nb zirconium alloy and 304L stainless steel with Nb and Ni hybrid interlayer was performed at 850–1050 ℃ under 4 MPa for 30 min. From 304L side to Zr-2.5Nb side, the typical interfacial structure of the 304L/Ni/Nb/Zr-2.5Nb joints was. (Ni, Cr, Fe) solid solution/Ni/Ni 3 Nb IMCs/Nb/(Zr, Nb) solid solution. Of the five layers, the nano-hardness of Ni 3 Nb IMCs layer was the highest, reaching ∼9.22 GPa for the joint bonded at 1000 ℃. With the increase of bonding temperature, the shear strength of the joint increased first and then decreased, and the maximum strength of 84.4 MPa was obtained at 1000 ℃. For the joint bonded at 1000 ℃, the fracture location was between the residual Ni layer and Ni 3 Nb IMCs layer, and the fracture type was a mixture of brittle fracture and ductile fracture.

THERMAL ANNEALING EFFECTS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF THE Ta-W-Ta SOLID PHASE JOINTS FOR NEUTRON PRODUCING TARGETS OF THE RESEARCH NUCLEAR FACILITY “SOURCE OF NEUTRONS”

The paper considers the neutron-producing tantalum-tungsten-tantalum target using a niobium interlayer manufacturing variant by means of vacuum hot roll bonding for the research nuclear facility «Source of Neutrons». The metallography results and the Ta-W-Ta solid-phase junction specimens mechanical testing ones obtained by hot roll bonding in vacuum, both immediately after production and after the heat treatment in the temperature range of 900…1300°C after roll bonding, are presented. The influence of thermal annealing on the interaction nature of the clad layers with each other and with the core tungsten material of the Ta-W-Ta solid-phase junctions with Nb interlayers obtained by vacuum hot roll bonding has been studied.

Ultra-high temperature oxidation resistance of a novel (Mo, Hf, W, Ti)Si2 ceramic coating with Nb interlayer on Ta substrate

In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack.

Investigating the bonding mechanism of P-TIG welded CpTi/Inconel 718 dissimilar joint with Nb interlayer

The direct joining of CpTi and Inconel 718 is challenging due to the formation of brittle TixNiy in the fusion zone. For the TIG welding of CpTi/IN718 joints in the present work, the use of Nb as an interlayer served as a barrier, resulting in the complete suppression of brittle TixNiy which is responsible for immediate failure of the CpTi/IN718 dissimilar joint. The results indicated that solid solution formed towards the CpTi side, whereas eutectic formation (NbNi3, Nb7Ni6) was observed towards the In718 side of the weldment. Owing to these brittle IMCs, a nanohardness of ∼14.62 GPa was measured at the Nb/IN718, which is ∼70% higher than that of the Nb/CpTi interface which was comprised of columnar dendrites. The tensile strength was 150 MPa with the presence of cleavage cracks at the Nb/IN718 interface of the fractured surface.

Strength optimization of two-step-bonded Ti-6Al-4V/Si3N4 joint with Nb interlayer via transient-liquid-phase bonding and active-metal brazing

A novel two-step bonding of Ti-6Al-4V/Si3N4 joint was developed with Nb interlayer as residual-stress reliever via low-pressure transient-liquid-phase bonding (TLPB) of Ti-6Al-4V/Nb side prior to active-metal brazing of Nb/Si3N4 side. While 1.75 mass% of Ti in a 50-µm-thick CUSIL-ABA® filler was sufficient for sound bonding at Nb/Si3N4 side when brazed at 1103 K for 10 min, one-step-brazed joints with bonding area of 10 × 10 mm2 were prone to failure at the Ti-6Al-4V/Nb side due to brittle Cu-Ti intermetallic compounds (IMCs). Replacing brazing of Ti-6Al-4V/Nb side with TLPB using pure Cu and Ni foils as filler at 1213 K for 180 min eliminated the formation of brittle IMCs via homogenization of (α + β)-Ti; bending strength increased to 193 MPa with residual-stress-induced failure from Si3N4 ceramics. Finally, effectiveness of stress-accommodation via Nb interlayer and filler’s plastic flow was quantitatively verified with reasonable fidelity by finite-element analysis incorporating temperature-dependent elasto-plastic properties.

Diffusion welding of CoCrNi Medium-entropy alloy (MEA) and SUS 304 stainless steel using different interlayers

With the emergence of entropy alloys, the scientific community has been persuaded to explore its joining issues for some stimulating and un-explored engineering applications. Currently, CoCrNi Medium-entropy alloy (MEA) is considered to be an excellent cryogenic material which can retain highest strength and ductility even at cryogenic temperature (i.e. 77 K). With such extravagant properties, authors compelled to explore the joining issues of this alloy. Therefore, the motivation of this research was to examine the weldability of CoCrNi MEA with the commercially available SUS 304 stainless steel using different interlayers. This research work was mainly concerned to investigate the effect of Ni, Cu, and Nb interlayers on bond formation and interface reaction during vacuum diffusion welding process. Results clinched that Ni-interlayered joints were free from the formation of Intermetallic Compounds (IMCs) and offered maximum shear strength (425.5 MPa). Cu-interlayered joints displayed the formation of Cr-C IMCs at Cu-SUS interface while Nb-Co, Nb-Ni and Nb-Cr-Ni phases were formed at Nb-MEA side. Formation of microvoids, cracks and presence of IMCs was observed in Nb-interlayered welded samples which caused lowest shear strength (238.12 MPa). Energy dispersive X-ray (EDX) and electron probe micro analysis (EPMA) were used to examine the diffusion thickness, diffusivities of constituent elements and other microstructural features across the welded joints. Scanning electron microscopy (SEM) scans and X-ray diffraction (XRD) was also executed on fractured surfaces to comprehend the joint formation mechanism.

Effect of ultrasonic peening treatment on microstructure and properties of CMT additive-manufactured Ti6Al4V/Al6.21Cu dissimilar alloys with Nb interlayer

The layer-by-layer ultrasonic peening treatment (UPT) was utilized to refine the coarse microstructure and decrease the pore number and size in the Al alloy of the Ti6Al4V/Al6.21Cu bimetallic structure with Nb interlayer manufactured by cold metal transfer additive manufacturing. After UPT, the pore in the deposited Al layer was compressed. Grains were compressed and refined significantly in the transition layer under the effect of UPT. The Nb interlayer still acted as the diffusion barrier and impeded the formation of harmful Ti-Al intermetallic compounds after UPT. The mean ultimate tensile strength of the bimetallic structure with Nb interlayer after UPT was 164.5 MPa, and increased by 36.1% compared to that of the bimetallic structure without UPT. The fracture occurred at brittle Al3Nb reaction layer for all samples.

Dissimilar Laser Welding of a NiTi Shape Memory Alloy to Ti2AlNb

NiTi-based shape memory alloys and the Ti2AlNb alloy have gained increasing importance in the aerospace field. The joining of these two materials can further increment the importance and usage of these relevant engineering materials and expand their potential applications. However, when joining NiTi-based shape memory alloys to Ti-based alloys, the formation of brittle Ti-rich intermetallic compounds often occurs, significantly limiting their functionality and use. Dissimilar joints between a NiTi shape memory alloy and Ti2AlNb alloy were obtained using a 0.1 mm thick Niobium (Nb) interlayer via laser welding. By process optimization, sound joints were obtained. The microstructure evolution was assessed by means of electron microscopy, whereas the mechanical strength of the joints was evaluated using lap shear tensile testing. The best performing joints were seen to fracture at maximum loads above 1230 N, thus allowing us to consider this dissimilar pair for structural applications.