TiFe Phase Research Articles

Magnetic Properties and Microstructure of Sm <sub>5</sub>Fe <sub>17</sub>-Based Composite Magnets

We have investigated synthesis, magnetic properties and microstructure of Sm5Fe17-based hard magnetic phase with a Sm20Fe70Ti10 composition. Ultrahigh coercivities, μ0Hc=7.18 T at room temperature and μ0Hc=8.86 T at 10 K, have been achieved. The room-temperature coercivity, determined from high-field pulse measurements, reaches 35% of the anisotropy field μ0Ha=20.7±0.8 T. Further, it is demonstrated that a coercivity of 2.18 T is maintained even at 500 K. The Curie temperature TC of Sm20Fe70Ti10 is 577 K and the calculated exchange stiffness parameter A is 7.72 pJ/m. Detailed transmission electron microscopy investigations show a two-phase microstructure consisting of the Sm5Fe17-based hard magnetic matrix phase with grain size below 200 nm and finer, below 100 nm, Fe2Ti grains. Majority of the Fe2Ti phase is located at the grain boundaries with some finer inclusions found also inside the 5:17 grains. Despite the high fraction of the Fe2Ti grains, nearly single-phase demagnetization loops are observed. In order to enhance Ms, the effect of Ti content on phase constitution, magnetic properties and microstructure was studied in detail. Ms increases and Hc decreases for the Ti-lean compositions.

Production of Fe–Ti Alloys from Mixed Slag Containing Titanium and Fe2O3 via Direct Electrochemical Reduction in Molten Calcium Chloride

High-purity intermetallic β-Ti (FeTi4) and FeTi alloys were prepared via molten salt electrolysis from a titanium-containing waste slag and Fe2O3 mixture using molten CaCl2 salt as the electrolyte. The mixed slag powders were pressed into a pellet that served as a cathode, while a graphite rod served as an anode. The electrochemical process was conducted at 900 °C with a cell voltage of 3.1 V under an inert atmosphere. The formation process of the alloys and the influence of the Ti:Fe atomic ratio on the product were investigated. With an increased proportion of Ti, the phase of the product changed from FeTi/Fe2Ti to FeTi/FeTi4, and different structures were observed. At a Ti:Fe ratio of 1.2:1 in the raw slag, an alloy with a sponge-like morphology and a small amount of FeTi4 were obtained. During the initial stages of electrolysis, a large amount of intermediate product (CaTiO3) was formed, accompanied by an abrupt decrease in current and increase in particle size. The current then increased and Fe2Ti alloy was gradually formed. Finally, as the reaction process extended inside the pellet, the current remained stable and the product mainly contained FeTi and FeTi4 phases. The observed stages, i.e., CaTiO3(TiO2) → Fe2Ti(Ti) → FeTi(FeTi4), were consistent with the thermodynamic analysis.

Microstructure, adhesion and erosion properties of Fe-Cr-Ti-Mo-C-Si coating with varying Titanium

The purpose of this study was to investigate the effect of titanium content on the microstructure, surface morphology, micro-hardness, adhesion and erosion properties of fabricated Fe alloy based coating materials. In this regard, Fe alloy based coating materials consisting of Fe, Mo, Si, C, Cr with varying Ti content were fabricated by High Velocity Oxygen fuel (HVOF) coating process. XRD results confirmed the formation of hardened Fe2Ti phase. Increase in 5 wt. % of titanium in the Fe based coating material increased the hardness and adhesion pull off strength by 20 % and 33 % respectively. The erosion wear rate of coating material was increased with the increase in impact velocity. However, in case of impingement angle, the erosion wear rate was increased for the increase in impingement angle from 0 to 60° but later decreased at 90°. The trend was attributed to the fact that erosion wear at impingement angle 60° was mainly influenced by micro-cutting erosion mechanism by normal and shear stresses but at impingement angle at 90°, the erosion wear rate mainly depends upon plastic deformation only due to normal stress.

Design of hydrogen separatinwg Nb-Ti-Fe membranes with high permeability and low cost

Nowadays, group 5B (Nb-, V-, and Ta-based) alloys are considered prospective candidates to replace commercial Pd-based hydrogen permeation membranes. In recent years, the focus of research efforts towards these metal membranes has been the development of robust/cheaper alloys and the exploration of related phase diagrams. To address this challenge, the phase diagram and solidification path of the Nb-Ti-Fe alloy system have been investigated within the CALPHAD (CALculation of PHAse Diagrams) approach by combining available experimental data. On this basis, Nb-Ti-Fe multi-phase hydrogen-permeable alloys have been designed and fabricated, and their microstructure, hydrogen permeability, and hydrogen embrittlement (HE) resistance were evaluated. The results obtained show four ternary invariant reactions and five phase regions in the liquidus projection, where the compositional region suitable for hydrogen permeation has been established successfully. Small variations in alloy composition (e.g. Nb or Ti/Fe ratios) can lead to large changes in hydrogen permeation properties. This is attributed to the TiFe phase in the eutectic structure transition from a continuous thin layer to discontinuous granules. In particular, Nb5Ti60Fe35 shows the highest permeability at 673 K, 3.82 × 10−8 mol H2 m−1 s−1 Pa−1/2, which, heretofore, is the highest value reported in this alloy system.

Thermodynamic modelling of magnetic laves phase in Fe–Ti system using first principle method

Phase diagram calculation of Fe–Ti system is obtained by coupling of CALPHAD with first principle methods. Single Gibbs energy model is used for FeTi to take care of order-disorder transition. First principle calculation shows that Laves phase is ferromagnetic nature with the magnetic moment of 1.417μB which is incorporated in the modelling. For extrapolation to higher order system, Laves phase is mostly expressed with two sublattice model. From crystallographic view, 3 sublattice model is appropriate one for description of Laves phase. Hence, two different models are used for Laves phase. Wagner-Schottky model used to describe the homogeneity region of Laves phase in two sublattice model. Using the first principle method, the energies of formation of unstable end members of FeTi phase and three sublattice model of Laves phase are calculated and incorporated as experimental data in optimisation. Calculated phase diagram and the thermochemical properties using 3 sublattice model of Laves phase shows good agreement with the experimental data.

Mechanical properties and microstructures of cast dental Ti-Fe alloys.

Binary Ti-Fe alloys of varying concentrations of Fe between 5-25% were made, and their castings evaluated in terms of microstructures formed and mechanical properties. The aim of this study was to explore the composition of Ti-Fe alloys that offers improved wear resistance of titanium. X-ray diffraction and microstructural observation revealed that 5-7% Fe, 8-15% Fe, and 20-25% Fe consisted of α+β, single β, and β+Ti-Fe phases, respectively. The hardness of alloys with 8-13% Fe was almost equal to that of Co-Cr alloys but lower than of the other Ti-Fe alloys. Elongation of the Ti-Fe alloys was negligible. However, dimples were observed in specimen containing 7-11% Fe. Alloys with 9% Fe demonstrated the highest strength of more than 850 MPa. We believe that Ti-Fe alloys with 8-11% Fe may be applicable in development of an alloy with good wear resistance due to the exhibited properties of high hardness and ductility albeit low.

Brazing TC4 titanium alloy/316L stainless steel joint with Ti50-xZrxCu39Ni11 amorphous filler metals

TC4 titanium alloy was brazed to 316L stainless steel with newly designed TixZr50-xCu39Ni11 amorphous filler metals. The effect of Zr content on the wettability of filler metals, interfacial microstructure and shear strength of the brazed joints was investigated. Precipitation behavior of submicron phase and fracture behavior of the brazed joints were analyzed. Increasing Zr content in filler metals first increased and then decreased the spreading area of filler metals on both TC4 titanium alloy and 316L steel substrates, and changed the primary phase in filler drops. Besides, residual filler metal layer was thickened due to the reduction of filler metal flowability. But the thickness of the transition zone decreased, particularly the α-Fe reaction layer, attributed to the attenuation of Ti diffusion from filler metal to 316L steel substrate. Submicron β-Ti phase precipitated near the FeTi/Fe2Ti interface, and there were orientation relationships among the submicron β-Ti phase, FeTi and Fe2Ti as follows: (110)FeTi||(110)β-Ti/[1(_)11]FeTi||[1(_)11]β-Ti and (100)FeTi||(100)β-Ti/[001]FeTi||[001]β-Ti. The shear strength of brazed joints first increased and then decreased with the peak value of 238 MPa at 22.2 at.% Zr. Stress concentration at FeTi/Fe2Ti interface and impossible orientation relationship between FeTi and Fe2Ti phases resulted in the brittle fracture at FeTi/Fe2Ti interface of the brazed joint.

Microstructural Evolution and Mechanical Properties of Ti Alloy/Stainless Steel Lap Joints during Cold Metal Transfer Technique with CuSi3 Filler Wire

Joining of dissimilar titanium (Ti) alloy to stainless steel is a very significant challenge during conventional fusion welding. In this study, cold metal transfer (CMT) technique is developed for lap joining of Ti alloy to stainless steel with CuSi3 filler wire. The microstructure evolution, mechanical properties and fracture mechanism of Ti alloy/stainless steel joints are investigated. When low heat input is applied, many fine spherical particles are distributed in the fusion zone, which are indicated as iron-rich phase in the Cu matrix. With an increase in the heat input, the particles become irregular and coarser in the fusion zone, inferring as Fe-Si-Ti ternary phase and Fe2Ti phase. Since the fractions of the melted Ti alloy and stainless steel increase, the reaction of Ti with Fe and Si becomes more intense and Fe-Si-Ti ternary phase and Fe2Ti phase thus appear in the fusion zone. The shear strength of the lap joints decreases with an increase in the heat input. There are two fracture modes in the lap joints, suggesting different fracture mechanisms. The fracture path of the joints is along the Ti-Cu interface under low heat input. The brittle Ti-Cu intermetallics are observed on the fracture surface, indicating that the shear strength and fracture feature of the joints are associated with the compound layer. The fracture failure of the lap joints occurs in the fusion zone under large heat input. The Fe-Si-Ti ternary phase and Fe2Ti phase have detrimental effects on the joint strength, resulting in a brittle fracture in the fusion zone.

Effect of rolling temperature on microstructure and mechanical properties of Ti/steel clad plates fabricated by cold spraying and hot-rolling

The effect of rolling temperature on the interfacial microstructure and mechanical properties of Ti/steel clad plates, fabricated by a newly designed method (cold spraying and hot-rolling), was studied. For this purpose, three rolling temperatures (i.e. 850, 950, 1050 °C) were selected to completely understand the bonding mechanism at Ti/steel interface. The type of interfacial compounds and thickness of the diffusion layers were found to be the main factors controlling the mechanical properties of the Ti/steel clad plates. Results showed that the Ti/steel clad plate rolled at 850 °C exhibited metallurgical bonding due to the formation of a 250 nm thick TiC diffusion layer at the interface, and resulted in the best elongation. In contrast, the sample rolled at 950 °C developed a 400 nm thick diffusion layer which was composed of TiC and FeTi compounds, leading to the best tensile strength. When the rolling temperature was increased to 1050 °C, the thickness of the diffusion layer (composed of coarse TiC and FeTi phases) was sharply increased to 4 μm, and the sample displayed poor tensile strength and elongation.

Hydrogen storage properties of Mn and Cu for Fe substitution in TiFe0.9 intermetallic compound

The present study investigates the partial substitutions of Mn and Cu for Fe in the TiFe-system to gain better understanding of the role of elemental substitution on its hydrogen storage properties. The TiFe0.88-xMn0.02Cux (x = 0, 0.02, 0.04) compositions were studied. From X-Ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA), it was found that all alloys are multi-phase, with TiFe as a major phase, together with β-Ti and Ti4Fe2O-type as secondary precipitates, of all them containing also Mn and Cu. Increasing the Cu content augments the secondary phase amounts. Low quantity of secondary phases helps the activation of the main TiFe phase for the first hydrogen absorption, but on increasing their amounts, harsher activation occurs. Both Mn and Cu substitutions increase the cell parameter of TiFe, thus decreasing the first plateau pressure. However, Cu substitution rises the second plateau pressure revealing the predominancy of electronic effects associated to this substitution. All samples have fast kinetics and high hydrogen capacity making these substituted compounds promising for large scale stationary applications.

The influence of refractory metals on the hydrogen storage characteristics of FeTi-based alloys prepared by suspended droplet alloying

The influence of the addition of refractory metals (molybdenum and tantalum) on the hydrogenation properties of FeTi intermetallic phase-based alloys was investigated. The suspended droplet alloying technique was applied to fabricate FeTiTa-based and FeTiMo-based alloys. The phase composition and hydrogen storage properties of the samples were investigated. The samples modified with the refractory metals exhibited lower plateau pressures and lower hydrogen storage capacities than those of the FeTi reference sample due to solid solution formation. It was observed that the equilibrium pressures decreased with the amount of molybdenum, which is in good agreement with the increase in the cell parameters of the TiFe phase. Suspended droplet alloying was found to be a practical method to fabricate alloys with refractory metal additions; however, it is appropriate for screening samples with desired chemical and phase compositions rather than for manufacturing purposes.

Effect of cobalt on the microstructure and hydrogen sorption performances of TiFe0.8Mn0.2 alloy

The microstructures and the hydrogen sorption performances of TiFe0.8Mn0.2Cox (x = 0, 0.05, 0.10, 0.15) and TiFe0.8Mn0.2-yCoy (y = 0.05, 0.10) alloys have been investigated. For TiFe0.8Mn0.2Cox alloys, the lattice parameters of TiFe phase decreased and the Laves phase contents increased with the addition of Co. With the increase of Co content in TiFe0.8Mn0.2Cox alloys, the maximum hydrogen storage capacities of TiFe0.8Mn0.2Co0.05 and TiFe0.8Mn0.2Co0.10 alloys decreased, but the effective hydrogen capacities increased, which is ascribed to the improved flatness of the α-β desorption plateau. Substitution of Co for Mn in TiFe0.8Mn0.2-yCoy alloys can effectively lead to single phase of TiFe alloys. Therefore, TiFe0.8Mn0.2-yCoy alloy showed a deteriorated activation property, but its effective hydrogen capacity increased remarkably due to the obviously improved flatness of the α-β desorption plateau. The addition of Co might adjust the change of the octahedral intersitial environment caused by Mn doping in TiFe phase, which contributes to the improved flatness of the α-β desorption plateau and hence the increased effective hydrogen capacity.

On the substitution of vanadium with iron in Ti–6Al–4V: Thermo-Calc simulation and processing map considerations for design of low-cost alloys

Two basic cost reducing concepts, manipulation of alloy chemistry and optimisation of the hot working process, were adopted in developing low-cost experimental titanium alloys that may be suitable for land-based applications. Iron, a low-cost beta stabilising element in titanium alloys, was used as a partial and full replacement for vanadium in ASTM grade 5 Ti–6Al–4V. Thermo-Calc simulations were first done on the Ti–6Al-xV-yFe alloy compositions (for y = 4 – x and x = 1–3) to predict the amounts of phases and the β-transus temperatures. Thereafter, the compacted powders of the different experimental alloys were melted and allowed to solidify in the electric arc furnace cold copper hearth. Optical and scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterise the alloys. Also, the hardness of the low-cost alloys was measured and compared to commercial Ti–6Al–4V. The Ti–6Al–1V–3Fe alloy was subjected to hot compression testing at various temperatures (750–950 °C) and strain rates (1-10 s-1) on a Gleeble 3500 thermomechanical simulator. Processing maps and microstructural validation were used to define the most suitable processing conditions. The stress exponent and apparent activation energy were also calculated using a hyperbolic-sine equation. The results show that the low-cost alloys with partial substitution of vanadium with iron contained only α-Ti and β-Ti phases with no TiFe phase. The hardness of the alloys increased with increase in iron addition. The stress exponent “n” value was less than 5 indicating that flow softening was not solely driven by dynamic recovery. The optimum processing conditions for hot working were found at ~900 °C and 0.1 s-1 strain rate. The alloy generally had a large processing window with the softening process controlled by mechanisms such as dynamic recovery, dynamic recrystallisation of prior beta grains, and dynamic alpha lath globularisation. In the region of 750–780 °C and 1.5–10 s−1 an area of unstable deformation was established which should be avoided during processing. This work shows that low-cost α+β titanium alloys containing iron can be manufactured using traditional ingot metallurgy techniques and loss of material due to processing-induced defects can be minimised or avoided during primary conversion process such as forging and rolling.

Cavitation Erosion and Corrosion Behavior of NiTi Cladding with Cu and Nb Interlayers

Cavitation erosion resistance of NiTi claddings by tungsten inert gas with/without Cu, Nb and Cu + Nb interlayers was investigated. The NiTi-TIG and NiTi-Nb-TIG claddings cannot resist the cavitation erosion due to the presence of cracks and brittle phase Fe2Ti. The employment of Cu and Cu + Nb interlayers can inhibit the welding cracks and brittle phase Fe2Ti. The ranking according to the cavitation erosion resistance is NiTi plate > NiTi-Cu-TIG cladding ≈ NiTi-Cu-Nb-TIG cladding > stainless steel. The superior cavitation erosion resistance of NiTi-Cu-TIG and NiTi-Cu-Nb-TIG claddings results from high hardness, superelasticity, no cracks and no brittle Fe2Ti phases. However, the corrosion resistance of NiTi claddings with Cu and Cu + Nb interlayers is slightly reduced due to the existence of the second phases and pores, compared with the NiTi plate.

Melt chemistry and redox conditions control titanium isotope fractionation during magmatic differentiation

Titanium offers a burgeoning isotope system that has shown significant promise as a tracer of magmatic processes. Recent studies have shown that Ti isotopes display significant mass-dependent variations linked to the crystallisation of Fe-Ti oxides during magma differentiation. We present a comprehensive set of Ti isotope data for a range of differentiation suites from alkaline (Ascension Island, Afar and Heard Island), calc-alkaline (Santorini) and tholeiitic (Monowai seamount and Alarcon Rise) magma series to further explore the mechanics of Ti isotope fractionation in magmas. Whilst all suites display an increase in δ49/47Ti (deviation in 49Ti/47Ti of a sample relative to the OL-Ti reference material) during magma differentiation relative to indices such as increasing SiO2 and decreasing Mg#, our data reveal that each of the three magma series have contrasting δ49/47Ti fractionation patterns over comparable ranges of SiO2 and Mg#. Alkaline differentiation suites from intraplate settings display the most substantial range of variation (δ49/47Ti = +0.01 to +2.32‰), followed by tholeiites (−0.01 to +1.06‰) and calc-alkaline magmas (+0.06 to +0.64‰). Alkaline magmas possess high initial melt TiO2 contents which enables early saturation of ilmenite + titanomagnetite and a substantial degree of oxide crystallisation, whereas tholeiitic and calc-alkaline suites crystallise fewer oxides and have titanomagnetite as the dominant oxide phase. Positive slopes of FeO*/TiO2 vs. SiO2 during magma differentiation are related to high degrees of crystallisation of Ti-rich oxides (i.e. ilmenite). Bulk solid-melt Ti isotope fractionation factors co-vary with the magnitude of the slope of FeO*/TiO2 vs. SiO2 during magma differentiation.This indicates that the modal abundance and composition of the Fe-Ti oxide phase assemblage, itself is controlled by melt composition, governs Ti isotope fractionation during magma differentiation. In addition to this overall control, hydrous, oxidised calc-alkaline suites display a resolvable increase in δ49/47Ti at higher Mg# relative to drier and more reduced tholeiitic arc suites. These subparallel Ti isotope fractionation patterns are best explained by the earlier onset of oxide segregation in arc magmas with a higher oxidation state and H2O content. This indicates the potential of Ti isotopes to be utilised as proxies for geodynamic settings of magma generation.

Ultrafine Fe-Fe2Ti eutectics by directed energy deposition: Insights into microstructure formation based on experimental techniques and phase field modelling

We investigated the Fe-Fe2Ti eutectic microstructure obtained by Directed Energy Deposition (DED) with a hypereutectic composition of Fe-17.6 at.% Ti. Ultrafine lamellar spacings as low as 200 nm were achieved, features which otherwise can only be obtained in thin specimens, e.g. by suction casting. However, at interlayer boundaries (ILBs) a globular morphology of the primary Fe2Ti phase is observed with halos of the Fe phase. For the given DED conditions the crystalline structure is thus discontinuous across the ILBs. Both 2D and 3D analysis methods were used to quantify the microstructure, including high resolution synchrotron holographic X-ray computed tomography (HXCT). The generic behaviour of eutectic systems under conditions that qualitatively correspond to those of laser additive manufacturing was explored by phase-field modelling for selected nucleation scenarios and alloy compositions spanning from eutectic to hyper-eutectic. While providing valuable insights into microstructure formation, the simulations point out the need to further deepen our understanding about melting under additive manufacturing conditions in order to implement suitable nucleation and / or free growth models. The simulations also show that globular ILBs can be prevented when using exactly eutectic alloy compositions.

Effect of welding speed on microstructure and mechanical properties of titanium alloy/stainless steel lap joints during cold metal transfer method

Cold metal transfer (CMT) technique is developed for lap joining of titanium (Ti) alloy to stainless steel (SS) with CuSi3 filler wire. The effect of welding speed on the microstructure and mechanical properties of Ti/SS lap joints is investigated. The results indicate that the wetting angle of the lap joints gradually increases and the weld width decreases with increasing the welding speed. It is found that many coarse phases in the fusion zone are rich in Ti, Fe and Si etc, inferring as Fe–Si–Ti ternary phase and/or Fe2Ti phase at low welding speed. Many fine spherical particles in the fusion zone are considered as iron-rich particles at high welding speed. The transition layer are exhibited at the Ti–Cu interface. With increasing the heat input, the intermetallic layer becomes thicker. A variety of brittle intermetallic compounds (IMCs) are identified in the lap joints. The shear strength of the joints increases with increasing the welding speed. Two fracture modes occur in the lap joints at low welding speed. Thicker reaction layer causes brittle fracture and poor joint strength. The Fe–Ti–Si and Fe2Ti phase within the fusion zone are detrimental to the joint strength. The fracture surface of the joints is dominated by smooth surface and tear pattern at high welding speed. The fracture mode of the joints is merely along the Ti–Cu interface.

Interfacial Investigation of Explosion-Welded Titanium/Steel Bimetallic Plates

Commercial pure titanium and low carbon steel were explosive welded. The interfacial structures were examined using a combined microstructural analysis and nanoindentation tests. The interface has a wavy morphology with an isolated mixing zone where a mixing of elemental titanium (Ti) and iron (Fe) occurs. Constituents in the mixing zone vary even under the same explosive welding conditions; for example, some are dominated by Fe2Ti intermetallics, whereas some consists of Fe2Ti and FeTi intermetallics. The nanoindentation tests and fracture observation confirm the brittle nature of the Fe-Ti intermetallics that formed in the mixing zone. The FeTi phase (~ 20.3 GPa) showed higher hardness than the Fe2Ti phase (~ 14.2 GPa). Simple approaches to estimate the cooling rate at the Ti/steel interface are proposed, and the calculated rate is 2.1 × 107 K/s. Such a high cooling rate combined with the chemical compositions results in the formation of the nanoscaled Fe2Ti structure in the mixing zone.

Structure and Phase Composition of Ti–6Al–4V Alloy Obtained by Electron-Beam Additive Manufacturing

The paper presents the fabrication of Ti–6Al–4V alloy specimens using two operating modes of the electron beam additive manufacturing (EBAM). The structure, phase composition and microhardness of the obtained alloy specimens are investigated. The EBAM process includes a deposition of Ti–6Al–4V wire onto a substrate comprising of VT1-0 (grade 2) titanium alloy and 12Kh18N10 (AISI 321) stainless steel. It is shown that at a high electron beam current, the height and width of the β-phase columnar grains are lower than at a low electron beam current. This phenomenon is discussed in terms of stabilization of the temperature gradient and the increased cooling rate during the building process. This phenomenon is caused by the formation of Fe2Ti, FeTi and Cr2Ti intermetallic phases in the diffusion bonding appeared between the titanium and stainless steel plates.

Interfacial microstructure and shear strength of Ti6Al4V alloy/316 L stainless steel joint brazed with Ti33.3Zr16.7Cu50−xNix amorphous filler metals

Ti33.3Zr16.7Cu50-xNix (x = 0–16.5, at.%) amorphous filler metals were designed to braze Ti6Al4V alloy and 316 L stainless steel (SS). The effect of Ni addition in filler metals on the wettability, joint microstructure evolution and shear strength were investigated. The reaction phase identification and crack initiation mechanism were analyzed in depth. Ni addition weakened the wettability of the filler metal and thickened the brazed seam. The filler metal with 11 at.% Ni was optimized for brazing of Ti6Al4V alloy/316 L SS with the maximum joint shear strength of 318 MPa. FeTi, Fe2Ti, FeCr, and α-Fe phases formed around the transition zone close to 316 L SS substrate, which was the weak part of the brazed joints. The interface between FeTi and Fe2Ti phases was non-coherent with the lattice mismatch of 61.4%, initiating the crack at (β-Ti + FeTi)/Fe2Ti interface. The initiative cracks mainly propagated along the Fe2Ti and FeCr layers with brittle feature. Optimizing the constituents and alloying process for Ti-Cu-based filler metal has huge potential in improving the performance of titanium alloy/steel joint.