Compound TiFe Research Articles

Effect of Ta/Ni dual-interlayer on the microstructure and properties of high strength titanium alloy and steel composite plate

The combination of ultra-high-strength Ti-6Al-4V (TC4) titanium alloy and 30CrNiMoNb (6211) steel was achieved by adding Ta/Ni dual-interlayer and rolling at 950 °C through welding a symmetrical blank sleeve with a vacuum electron beam. In order to unveil the metallurgical bonding mechanism and the interfacial structure, SEM, XRD, and compression-shear performance tests were used. The results revealed the presence of thin-film brittle TiC, TiFe, and TiFe2 compounds at the TC4/6211 interface, resulting in an increased risk of interface mismatch and brittle fracture along the matrix phase interface, and the average interfacial bonding strength was tested at 323 MPa.In contrast, the TC4-Ta interface and the 6211-Ni interface in the TC4/Ta/Ni/6211 composite plate displayed good solid solution formation. The strengthening mechanism of the Ta/Ni dual-interlayer interfacial bonding was analyzed using selected area electron diffraction (SAED), revealing that the Ta-Ni diffusion region consisted of Ni3Ta and Ni2Ta. The addition of the Ta/Ni dual-interlayer prevented the aggregation of Ti and Fe atoms to form Ti-Fe compounds. The malleable intermetallic compounds of Ni3Ta and Ni2Ta effectively coordinated deformation, leading to an average interfacial bonding strength of 469 MPa, which was 45.2 % higher than the composite plate without Ta/Ni dual-interlayer.

Interfacial modification of titanium/steel composites and its effect on the growth pattern of Fe-Ti compounds

The formation of brittle compounds at the titanium/steel interface, which weakens bonding strength, is a significant challenge that must be addressed to broaden its use in sectors like petrochemical engineering and pressure vessels. Previous research has improved bonding strength by adjusting the diffusion coefficient on the titanium side. However, it also revealed problems with the rapid increase in TiC layer thickness and the precipitation of Fe-Ti compounds at temperatures above 950°C. This study introduces a new method based on the coordinated control of titanium/steel diffusion coefficients to create a TiC barrier effect at the interface, thus preventing the formation of brittle Fe-Ti compounds. The research methodically examines the effects of coordinated diffusion coefficient control between 850°C and 1000°C on the composite interface structure and further enhances bonding strength. The findings show that the coordinated control of titanium/steel diffusion coefficients effectively stabilizes the interface structure as α-Ti, TiC, and γ-Fe, inhibiting the formation of Fe-Ti compounds. As the rolling temperature rises from 850°C to 1000°C, the bonding strength increases from 190 MPa to 340 MPa. Near the composite interface on the steel side, a (101) oriented layer forms, and the diffusion distance of carbon significantly decreases to 10μm. The composite interface layer transitions from a mixed layer of TiC and Fe-Ti with a thickness of approximately 470 nm to a uniform and continuous TiC layer about 200 nm thick. This breakthrough overcomes the limitations of rolling temperature and excessive thickening of interface brittle compounds, expanding the process window for titanium/steel composite material preparation and establishing a link between diffusion coefficients, interface structure, and mechanical properties.

Effects of Interlayer on the Microstructure and Mechanical Properties of Resistance Spot Welded Titanium/Steel Joints: A Short Review

In this paper, the influence of interlayer on titanium/steel dissimilar metal resistance spot welding is reviewed from the aspects of macroscopic characteristics, microstructure and interface bonding properties of the joint. Previous studies have demonstrated that TiC, FeTi and Fe2Ti intermetallic compounds with high brittleness are formed in the joint during titanium/steel welding, which reduces the strength of the welded joint. Researchers proposed different interlayer materials, including Cu, Ni, Nb, Ta, 60%Ni-Cu alloy and BAg45CuZn. Firstly, adding an interlayer can weaken the diffusion of Fe and Ti. Secondly, the interlayer elements can combine with Fe or Ti to form solid solutions or intermetallic compounds with lower brittleness than Fe–Ti compounds. Finally, Cu, Ni, Ag, etc. with excellent ductility can effectively decrease the generation of internal stress, which reduces the formation of defects to improve the strength of the joint.

Laser metal deposition of titanium on stainless steel with high powder flowrate for high interfacial strength

Direct joining of titanium and stainless steel 316 L with a strong interface is very challenging due to the formation of the brittle intermetallic compounds FeTi and Fe2Ti in the intermixing zones and to the high residual stress induced by the mismatch of the thermal expansion coefficients. In this bimetallic directed energy deposition study, firstly, deposition of Ti on stainless steel was carried out using conventional process parameter regime to understand the interfacial cracking susceptibility and then a novel high powder flowrate approach is proposed for controlling the dilution and constraining the intermetallic phases forming at the interface. The influence of high temperature substrate preheating (520 °C) on the cracking susceptibility and interface strength was also investigated. The deposited Ti samples and their interfaces with the 316 L substrate were characterized with optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy to investigate the geometry, microstructures and chemical compositions in relation to the cracks. The high powder flowrate deposition of Ti on stainless steel 316 L results in an extremely thin dilution region (~ 10 μm melt pool depth in the substrate) restricting the formation of the intermetallic phases and cracks. The ultimate shear strength of the interfaces of the crack free sample was measured from cuboid deposits and the highest measured strength is 381 ± 24 MPa, exceeding the weaker base material pure Ti. The high interfacial strength for high powder flowrate deposition is due to the substantial attenuation and shadowing of the laser beam by the in-flight powder stream as demonstrated by the high-speed imaging resulting in an extremely small dilution region.

Direct energy deposition of functionally graded layers for the Ti–Fe compound

In the process of joining dissimilar materials, the formation of large amounts of intermetallics and the interaction of active materials were reduced. The influence of thermal cycles in the cladding process makes a significant contribution to the formation of the structural-phase composition and mechanical properties of the heterogeneous Ti–Nb–Cu–Fe joint. As the interpass temperature increases, the fusion depth increased, as the rate of diffusion processes. It is shown that the formation of intermetallides such as FexTi, TixCu, FexNb, etc. can be reduced by the variation of the interpass temperature. The best mechanical properties were obtained at an interpass temperature of 10 s, and the ultimate strength was up to 325 MPa.

ANALYSIS OF TiFe INTERMETALLIC COMPOUND BY DFT

The structural, mechanical, anisotropy, and optical properties of the TiFe compound, which is the effective hydrogen storage material, were analyzed using the DFT method with the CASTEP program. The elastic constants of the cubic system, which have been determined by the stress-strain method, are stable according to the Born stability criteria. According to the mechanical properties, the compound was brittle and hard. Anisotropy properties were examined in 2D and 3D with the EIAM code. Finally, the optical properties using the complex dielectric function based on the electronic structure of TiFe; parameters such as dielectric constants, reflectivity, extinction coefficient, refractive index, and loss function were examined in the range of 0-50 eV. Generally, our obtained results are comparable with literature values.

Microstructure and mechanical properties of Ti-6Al-4V/316L dissimilar materials with FeCrCuV medium-entropy alloy transition layer by laser metal deposition

To avoid brittle intermetallic compounds during direct connection of the Ti-6Al-4V alloy and 316L stainless steel, the FeCrCuV medium entropy alloy (MEA) is designed as the transition layer, and the 316L/FeCrCuV/Ti-6Al-4V dissimilar materials are fabricated by laser metal deposition (LMD). The heterogeneous interfaces of 316L/FeCrCuV and FeCrCuV/Ti-6Al-4V are investigated by a scanning electron microscope (SEM), an energy dispersive spectroscope, and electron backscatter diffraction. The results indicate that common brittle intermetallic compounds TiFe and TiFe2 at Ti-6Al-4V/316L heterogeneous interfaces disappear, and the BCC/FCC dual-phase solid solution structure is obtained due to the solid solution effect of the FeCrCuV transition layer. Refined grains appear at heterogeneous interfaces of 316L/FeCrCuV and FeCrCuV/Ti-6Al-4V for the rapid cooling rate during LMD, which results in fine grain strengthening. The microhardness near heterogeneous interfaces increases the solution strength and fine grain strengthening. Furthermore, the design of the FeCrCuV transition layer with a dual-phase structure improves the coordinated deformation ability of 316L/FeCrCuV/Ti-6Al-4V and results in higher tensile strength.

A novel approach to optimize weld formation and regulate interfacial microstructure in TC4/304SS dissimilar arc welding by active hybrid shielding gas

CO2 shielding gas was innovatively employed for TC4/304SS dissimilar metal arc welding, overcoming the limitation of active gas application for Ti welding. The effect of CO2 addition on welding process was investigated. Our results show that the CO2+Ar hybrid shielding gas eliminated the problem of insufficient bonding at the backside of the steel plate, and was helpful to obtain a full weld joint. Moreover, the microstructure of the weld joint was modified due to the intense mass transfer inside the molten pool. The typical Ti/Cu interface was divided into two layers. No Ti–Fe compounds were found within the Ti/Cu interface for pure Ar shielding gas. However, the interface morphology was found to change due to induced CO2. Some TiFe2+Ti5Si3 dendrites were formed in layer Ⅱ. And the TEM results showed that the addition of CO2 did not contribute to the generation of a new phase, but the island-shaped Ti2Cu3 was transformed to a lath shape. In the weld seam center, Ti–Fe–Si ternary compounds was formed instead of Ti–Fe or Ti–Cu compounds. The hardness of the entire joint increased with increasing CO2 content. An average strength of 480 MPa was obtained for 3% CO2 content, which is an increase of 57.9% compared to that for pure Ar shielding condition. The fracture surface morphology showed small cleavage flatforms with some shallow dimples. Better weld formation and the optimization of the interface microstructure both contributed significantly to the improvement of the tensile strength of the Ti/steel joint.

Sintesis dan Karakterisasi Fe₂TiO₅ dari Besi Oksida dan Titanium Dioksida dengan Metode Planetary Ball-Mill

The method of solid hydrogen storage through integration in metal hydride compounds is a new, promising method. This research has succeeded in synthesizing and characterizing the metal hydride alloy Fe-Ti system through a planetary ball-mill process. Based on the XRF analysis, it was found that the composition of Fe oxide content reached 56.22% while Ti oxide reached 43.78%. The FTIR study showed absorption at wavenumbers of 900 cm-1 and 500 cm-1. Both are typical absorptions for Ti-O and Fe-O groups, suggesting that the synthesized sample was successful. It can be seen from the XRD data that some of the diffractogram peaks of the resulting Fe-Ti compound match the peaks of the Fe2TiO5 and TiO2 compounds obtained from the Powder Diffraction File (PDF) database number 00-003-0374. After the refinement was performed, information was obtained that the synthesis of Fe-Ti alloy material using the planetary ball mill technique produced Fe2TiO5.

Investigation of Hybrid Lap Welds of TI6AL4V and Stainless Steel with Bronze Interlayer

Abstract Welding of the austenitic stainless steel AISI 304 and Ti6Al4V is complicated by hard and brittle intermetallic compound formation. In this contribution, we study a laser welding method that partially overcomes this problem using interlayer. Bronze foil (CuSn6) of thickness 100 µm and 200 µm was inserted between steel and titanium sheets and lap welds were realized on pulsed Nd:YAG laser. Representative samples were investigated by nanohardness measurement, SEM/EDS, and XRD analysis to detect the localization of the intermetallic phases. The macrostructure of the weld cross sections was displayed by optical and digital microscopy. The nano-hardness test revealed the presence of very hard intermetallic mainly around the interface between the fusion zone and bottom metal sheet. EDS mapping displayed the main elements Fe, Cr, Cu and Ti distribution in the fusion zone, EDS line scanning detected elements‘ signals in the diagonal and horizontal directions. XRD analysis revealed expected intermetallic compounds FeTi and CuTi2 and solid solution Cu0.8Fe0.2.

Diffusion behavior and formation mechanism of compounds in titanium-steel bonding process at high temperature

In this research, titanium-steel diffusion bonding experiments were carried out to interpret the elements’ diffusion behavior and the compounds’ formation mechanism during the heating process of hot-rolling titanium-steel clad plates. The results show that the reaction–diffusion of C and Ti atoms mainly happened in the contact region when heating at 850 ℃ and formed some weak combined zone. The crystal structure transformation caused a shift in the diffusion behavior of Fe, C, and Ti elements. Moreover, the TiC existed in two forms in the interfacial reaction layers at 900 ℃: the particles diffusely distributed in the FeTi layer and the continuous or semi-continuous ribbon distributed between FeTi and Fe2Ti. The formation of Ti-Fe compounds was predominant at higher temperatures.

Microstructure evolution and crack propagation mechanism during laser lap welding of Ti6Al4V and DP780 steel with CoCrNi powder

Joining steel and Ti alloys is important for aerospace applications. However, the brittle intermetallic compounds (IMCs) formed during welding of steel and Ti alloys are prone to cracks, which limit the preparation of high-strength steel/Ti joints. In this work, CoCrNi powder was used as an intermediate alloy to reduce the tendency of these brittle phases to produce cracks. The addition of this CoCrNi powder ensured that good quality joints were obtained and no cracks were observed. Three elements of CoCrNi are capable of infinite solid solution with Fe, so the alloy powder does not form a large amount of brittle IMCs with Fe by laser melting. A region of Fe-Ti IMCs formed at the steel/Ti interface due to the mixing of Fe and Ti. Moreover, the diffusion of CoCrNi from the melt pool into the Fe-Ti IMC interface layer reduced the interface layer brittleness, decreased the interface layer cracking tendency and improved joint performance. The plastic toughness of the interface layer of Fe-Ti compounds significantly improved after the addition of Co, Cr, and Ni alloying elements, which fully demonstrated the effectiveness of CoCrNi powder incorporation.

Tic production on steel with cathodic arc based -diffusion process

ABSTRACT A coating-diffusion method based on cathodic arc physical deposition (CA-PVD) is introduced for the production of titanium carbide on steel substrates. The method allowed the production of TiC layer in a temperature range of 1000–1200°C in a controlled manner. The Fe–Ti compounds forming at the initial diffusion states are the source of iron in TiC. The free energy of formations indicated that Fe–Ti alloying at the interface takes place after depletion of C. The initially formed TiC layer does not grow in layer mode and kinetically hinders the reaction between carbon depleted zones in the steel. As the process proceeds, iron in the Fe–Ti compounds at the substrate diffusion layer interface is released with the carburization of titanium and carried towards the surface either by deposited fresh titanium layers or macroparticles. Macro particles played an essential role in collecting and carrying iron to the surface of the TiC layer.

Effect of carbon content on the microstructure and bonding properties of hot-rolling pure titanium clad carbon steel plates

The effect of carbon content on the microstructure and bonding properties of pure titanium clad carbon steel plates was studied by performing hot-rolling bonding experiments on pure titanium/carbon steel with different carbon contents. Results showed that at 850 °C, the higher the carbon content of the steel used in the experiment, the lower the bond strength of the composite plate. At 1050 °C, the higher the carbon content of the steel used in the experiment, the thicker the preferential TiC layer generated, the stronger the capability to hinder the formation of Fe–Ti compounds, and the higher the bond strength of the composite plate obtained. During hot rolling, TiC was preferentially formed on the interface of pure titanium/carbon steel, and it could effectively reduce the mutual diffusion between Fe and Ti, thus preventing the formation of Fe–Ti compounds. In actual industrial production, when pure titanium and carbon steel are bonded by hot rolling, a reasonable rolling temperature can be selected according to the carbon content of steel to obtain a composite plate with high bonding strength.

Density functional theory study on the role of ternary alloying elements in TiFe-based hydrogen storage alloys

The role of additional ternary alloying elements on the performance of stationary TiFe-based hydrogen storage alloys was investigated based on first-principles density functional theory calculations. As a basic step for examinations, the site preference of each alloying element in the stoichiometric and non-stoichiometric B2 TiFe compounds was clarified considering possible anti-site defects. Based on the revealed site preference, the effect of various possible ternary elements on the hydrogen storage was examined by focusing on the formation enthalpies of TiFeH and TiFeH2 hydrides, which were closely related to the change in the location of plateaus in the pressure−composition−temperature curve. Several physical properties such as the volume expansion due to hydride formation were also examined to provide additional criteria for selecting optimum alloying conditions in future alloying design processes. Candidate alloying elements that maximize the grain boundary embrittlement due to the solute segregation were proposed for the enhanced initial activation of TiFe-based hydrogen storage alloys.

Joining of Cf/SiC and stainless steel with (Cu–Ti)+C composite filler to obtain a stress-relieved and high-temperature resistant joint

In this study, to obtain a stress-relieved and high-temperature resistant joint of Cf/SiC composite and stainless steel at relatively lower brazing temperature, reaction composite-diffusion brazing with the mixed powders of Cu–15Ti alloy and C particles as filler material was used to join Cf/SiC composite and nickel-plated stainless steel. Results show that C particles reacted with Cu–Ti alloy filler with low melting point not only formed a composite joining layer which can relieve residual stress in the joints, but also formed a heat resistant (Cu)ss matrix due to the consumption of the melting point depressant element Ti. Meanwhile, the nickel plating diffused melting raising element Ni into the joining layer formed a (Cu,Ni)ss matrix with higher heat resistance, further improving the heat resistance of the joining layer, so the filler isothermally solidified in a short time during the brazing process. In addition, the nickel plating also prevented the formation of the brittle compound TiFe that may cause crack at the interface of joining layer/stainless steel. As a result, a stress-relieved joint with high-temperature resistance was obtained at relatively lower brazing temperature, and the maximum shear strength of the joint reached 233.4 ± 21.3 MPa, which is 51.3% higher than that brazed with Cu–15Ti alloy alone.

Femtosecond Laser-Induced Periodic Surface Structures on 2D Ti-Fe Multilayer Condensates.

2D Ti-Fe multilayer preparation has been attracting increased interest due to its ability to form intermetallic compounds between metallic titanium and metallic iron thin layers. In particular, the TiFe compound can absorb hydrogen gas at room temperature. We applied femtosecond laser pulses to heat Ti-Fe multilayer structures to promote the appearance of intermetallic compounds and generate surface nanostructuring. The surface pattern, known as Laser Induced Periodic Surface Structures (LIPSS), can accelerate the kinetics of chemical interaction between solid TiFe and gaseous hydrogen. The formation of LIPSS on Ti-Fe multilayered thin films were investigated using of scanning electron microscopy, photo-electron spectroscopy and X-ray diffraction. To explore the thermal response of the multiple layered structure and the mechanisms leading to surface patterning after irradiating the compound with single laser pulses, theoretical simulations were conducted to interpret the experimental observations.

Interface Control in Additive Manufacturing of Dissimilar Metals Forming Intermetallic Compounds-Fe-Ti as a Model System.

Laser metal deposition (LMD) has demonstrated its ability to produce complex parts and to adjust material composition within a single workpiece. It is also a suitable additive manufacturing (AM) technology for building up dissimilar metals directly. However, brittle intermetallic compounds (IMCs) are formed at the interface of the dissimilar metals fabricated by LMD. Such brittle phases often lead to material failure due to thermal expansion coefficient mismatch, thermal stress, etc. In this work, we studied a Fe-Ti system with two brittle phases, such as FeTi and Fe2Ti, as a model system. Fe was grown on top of Ti at various process parameters. The morphologies and microstructures were characterized by optical microscopy (OM) and scanning electron microscopy (SEM). No cracks along the interface between pure Ti and bottom of the solidified melt pool were observed in the cross-sectional images. Chemical composition in the fabricated parts was measured by Energy-dispersive X-ray spectroscopy (EDS). Electron backscatter diffraction (EBSD) was performed in addition to EDS to identify the crystalline phases. The Vickers hardness test was conducted in areas with different phases. The chemical composition in the melt pool region was found to be a determining factor for the occurrence of major cracks.

Machine learning-assisted discovery of strong and conductive Cu alloys: Data mining from discarded experiments and physical features

Copper alloys with high strength and electrical conductivity are ideal candidates for a wide range of civilian and engineering applications. Traditional methods of alloy design, such as “trial and error” experiments, are costly and time-consuming, limiting the discovery of Cu alloys. Machine learning (ML)-based technology facilitates a better understanding on inter-relationships within massive experimental datasets, and shortens the development cycle of new alloy systems. Herein, we propose a method of material design based on ML to discover high-performance Cu alloys. The ML models are trained from “discarded” experimental data that show undesirable hardness and/or electrical conductivity. We constructed effective Gaussian process regression-based models successfully from limited training data by engaging additional features. The predicted Cu alloys were experimentally synthesized and characterized, exhibiting superior hardness or electrical conductivity with respect to original training data. The increase of hardness is due to precipitation of second-phase Co-Ti and Fe-Ti compounds during aging, while the rise of electrical conductivity is caused by a purification effect of the precipitates on Cu matrix. The impact of physical features on ML models was further evaluated by a genetic algorithm. Our findings suggest that ML holds great potential for developing high-performance Cu alloys.

The Effect of Laser Offset Welding on Microstructure and Mechanical Properties of 301L to TA2 with and without Cu Intermediate Layer

Based on dissimilar materials of 301L/TA2, the effect of laser offset and copper intermediate layer on welded joints was investigated. First, the process optimization of laser offsets indicated that the tensile strength of welded joint without intermediate layer was reached to the highest value when the laser was applied on the TA2 side. On the other hand, the tensile strength of welded joint with intermediate layer performed well when laser was applied in the middle position. Then, microstructural characterization and mechanical properties of welded joints were observed and tested. Based on eutectic reaction and peritectic reaction: TiFe and TiFe2 compounds were produced for welded joint without intermediate layer. Cu-Fe solid solutions and Cu-Ti compounds were generated when copper was used as the intermediate layer. The maximum tensile strength of welded joint with and without copper intermediate layer were 396 and 193 MPa, respectively. Finally, fracture mechanism of 301L/TA2 welded joint was studied: Fe-Ti compounds caused brittle fracture of welded joints without intermediate layer; brittle fracture took place in rich copper and Cu-Ti compounds area of welded joints with copper intermediate layer.