Single Bcc Phase Research Articles

Development of Fe-Mg alloys with intermediate degradation kinetics as potential biodegradable bone implants

This paper reports the production and characterizations of some Fe-xMg (x=3, 5, 7 wt.%) alloys. These Fe-Mg alloys were prepared using the mechanical alloying method followed by low-temperature sintering. The influence of the addition of various Mg contents on the microstructures, hardness, and degradation characteristics of these alloys were examined. The microstructure analyses demonstrated the homogeneous distribution of Fe and Mg in the alloys with a single-phase BCC structure. The inclusion of Mg was found to affect the alloys’ porosity, particle morphology, grain size, formation of corrosion products, and degradation behaviors. The corrosion products obtained from the alloys using the electrochemical and weight loss measurements indicated that their degradation rates (in the range of 3.13–4.7 mm/year) are in-between those of pure Fe and Mg. It was asserted that the Fe-Mg can be an appealing alternative for temporary medical implants. Furthermore, this study may establish an essential foundation for the degradation control of Fe-based implants by including more active elements.

Stress increase by nanoscale hcp precipitates in HfNbTaTiZr high entropy alloys

HfNbTaTiZr high entropy alloys show a stress increase around 873 K, especially in the single crystals. At 873 K, the bcc single phase is decomposed into the bcc1 and bcc2 phases due to spinodal decomposition with composition modulation along <100> direction. The bcc1 phase has Zr- and Hf-rich composition, while Nb and Ta are enriched in the bcc2 phase. Next, the hcp phase is precipitated along the bcc1 phase. As a result, the hcp phase is aligned parallel to {100} plane of the bcc phase. The fine hcp phase acts as a strong barrier to the dislocation motion, resulting in the stress increase at 873 K.

Electrochemical corrosion behavior of Nbx(MoTaW)(1−x) (x = 0.25, 0.4, 0.55, and 0.7) refractory multicomponent alloys

The current study investigates the effect of increasing Nb concentration in Nbx(MoTaW)(1−x) refractory multicomponent alloys (RMCAs) on corrosion behavior in 3.5 wt% NaCl. The as-processed alloys showed a single-phase BCC crystal structure. With increasing Nb content, the open circuit potential values increase towards the positive direction, which indicates the formation of a stable oxide layer. In addition, polarization curves of RMCAs showed the passive layer formation, while pitting was not observed upto 2 V. The corrosion rate decreased as the Nb content increased, which may be attributed to the presence of coarse grains in high Nb-content RMCAs. Finally, the corrosion resistance of Nb0.7(MoTaW)0.3 is high compared to other alloys. Following the corrosion test, the presence of pits was not observed, indicating uniform corrosion, which is also corroborated by polarization data. X-ray photoelectron spectroscopy detected the presence of Nb2O5, Ta2O5, WO3 and MoO3 in the oxide layer, showing the active participation of all alloying elements in the corrosion process.

Microstructure evolution and high-temperature erosion behaviors of laser cladded AlxCoCrFeNi2.1 HEA coatings

High entropy alloys (HEAs) are anticipated to be candidates for high-temperature applications. In this work, high-speed laser cladding has prepared AlxCoCrFeNi2.1 (1≤x≤1.4) HEA coatings with high Al content. The effects of Al content on the microstructure, microhardness, and high-temperature erosion behaviors have been systematically investigated. With the increase of Al content, the coating’s microstructure transforms from the dual-phase structure of FCC and BCC to a single-phase BCC structure. Correspondingly, the microhardness of HEA coating gradually increases at room temperature due to the increment of BCC proportion. The Al1.4 HEA coating, consisting of a single BCC phase, exhibits the highest resistance to solid-particle erosion at 600℃, while Al1.0 coating with FCC and BCC dual-phase structure takes the second place. Ploughing, fracture, and spalling occurred during the high-temperature erosion process of AlxCoCrFeNi2.1 HEA coatings. The synergistic interaction between the FCC and BCC phases in dual-phase coatings primarily influences erosion behaviors. However, oxidation resistance is critical to erosion resistance for single-phase BCC coatings.

Microstructural evolution and mechanical properties of FeNiVAlx medium-entropy alloy

FeNiV alloys exhibit potential applications in magnetic, radiation-resistant, mechanical, and superconducting fields, however, the formation of the hard yet brittle sigma phase enriched with Fe and V hindered their application in extreme environments. Therefore, improving the mechanical properties of FeNiV alloys has been a crucial problem. In this study, a series of as-cast FeNiVAlx (values of x is 0, 0.1, 0.2, 0.3) medium-entropy alloys (MEAs) were fabricated by vacuum arc melting, and the evolution of microstructure and mechanical properties with different Al microalloying were investigated systematically. As the Al content increased, FeNiVAlx MEAs underwent a structural transformation from a dual-phase structure consisting of a FCC phase (46.4 %; phase content) and a sigma phase (53.6 %) at x=0 to a single BCC phase in FeNiVAl0.3, while the mechanical properties of the alloy show a decrease in strength and a significant increase in elongation. Notably, the FeNiV alloy exhibits the highest yield strength of 1851 MPa with 7.8 % ductility. In contrast, the FeNiVAl0.2 alloy demonstrated superior comprehensive compressive properties, with a high yield strength of 1255 MPa and an exceptional ductility exceeding 50 % without fracturing. The elimination of the harmful sigma phase, coupled with the formation of BCC phase, contributes to the observed decrement in strength and increment in ductility. This study elucidates the intrinsic relationship between microstructure and mechanical properties with Al contents in FeNiVAlx alloys, providing insights for the design of MEAs with excellent strength-ductility balance through microalloying.

High-throughput screening of MoNbTaW-based Refractory High-Entropy Alloys through Direct Energy Deposition in-situ alloying

Refractory High-Entropy Alloys (RHEAs) have been presented as attractive materials for high-temperature applications, such as combustion engines for the aerospace sector, due to the possible service temperature increase, which can result in superior yield of the combustion itself. This work presents the combination of CALPHAD simulations with the in-situ alloying of the MoNbTaW system by Direct Energy Deposition (DED) for a high-throughput screening of RHEAs. CALPHAD simulations show that the addition of V and Ti allows a single-phase BCC structure to be kept. For the DED setup available, MoNbTaW single-track deposits were optimised through Response Surface Methodology. Afterwards, in-situ alloying with V was conducted. Microstructural characterisation was assessed at room temperature through SEM/EDS, and the mechanical characterisation was performed at room temperature (RT), 350 °C and 700 °C, through nanoindentation tests. The microstructural characterisation shows that alloying up to 40 at.% V to the base system allows to keep a single-phase structure; however, some segregations are observed. Mechanical characterisation revealed that V alloying of 22 % promotes a 93 % increase in hardness at RT and a 150 % increase at 700 °C. This study contributes to increasing the practical knowledge of RHEAs, thus accelerating the application of these alloys in aerospace applications.

A single-phase Nb25Ti35V5Zr35 refractory high-entropy alloy with excellent strength-ductility synergy

Refractory high entropy alloys (RHEAs) are promising candidates for high-temperature structural materials due to their excellent high-temperature performance. However, the room-temperature brittleness of most alloys results in poor plastic formability, thereby limiting their engineering applications. In this study, Nb25Ti35V5Zr35 alloy with cold-rollability was developed, and its phase stability, tensile mechanical properties, elastic properties, strengthening mechanism, and deformation mechanism were investigated by combining experiments, CALPHAD, DFT and molecular statics (MS) methods. The results demonstrate that Nb25Ti35V5Zr35 alloy possesses good phase stability, with both the as-cast and annealed states maintaining a single-phase BCC structure without undergoing phase transformation. The tensile yield strength of the alloy reaches its peak at 1152 MPa in the cold-rolled condition, while its annealed state exhibits an optimal balance of strength and plasticity, with a yield strength of 836 MPa and an elongation of 22.45 %, respectively. Solid solution strengthening is the primary source of its high strength, with V and Zr playing key roles in this strengthening mechanism. Dislocation slip plays a dominant role in plastic deformation. Additionally, compared to traditional BCC alloys, the significance of edge dislocations in the deformation process is notably enhanced, with the {112} plane serving as the preferred slip plane for dislocations. DFT results indicate that the alloy exhibits significant anisotropy in both Young's modulus and shear modulus. This work contributes to understanding the material properties of the Nb25Ti35V5Zr35 alloy and provides a reference for the design of new ductile RHEAs.

Powder metallurgical processing of novel Al0.5CoCrFeNiNb0.5-Si0.1 high entropy alloys: Phase evolution and nanomechanical properties

In this research, the high entropy alloy (HEA) of Al0.5CoCrFeNiNb0.5-Si0.1 was successfully synthesized through mechanical alloying utilizing a high-energy planetary ball mill. The synthesized HEA powder was subsequently pressed and sintered at 1400 °C with varying holding times. The phase evolution was investigated using X-Ray Diffraction (XRD) technique. Furthermore, the microstructural, morphological, and compositional characteristics of the powders were examined using Transmission Electron Microscopy (TEM) with Selected Area Electron Diffraction (SAED), as well as Scanning Electron Microscopy (SEM) in conjunction with Energy Dispersive Spectroscopy (EDS). The nano-mechanical properties of the HEA compact were evaluated through nanoindentation to determine nano-hardness and elastic modulus.The mechanical alloying process was conducted for a duration of 30 h, resulting in the formation of a single-phase BCC solid solution, as confirmed by XRD and SAED analyses. The study investigated the criteria for phase stability based on the minimum Gibbs free energy and Hume-Rothery rules, which were consistent with the observed microstructural characteristics. Furthermore, the sintering process resulted in porosity levels of 6.01 % and 4.71 %, with corresponding densities of 6.96 g/cm³ and 7.12 g/cm³ for holding times of 3 and 4 h, respectively. It was noted that extended holding times improved the mechanical properties, with the alloy achieving a maximum hardness of 546 HV, nano-hardness of 5.57 GPa, elastic modulus of 265.47 GPa, and yield stress of 1.89 GPa after a holding time of 4 h.

Accelerated discovery of multi-property optimized Fe–Cu alloys

The next generation of rotating electrical machines requires materials with an optimized combination of magnetic, electrical and mechanical properties. High-throughput experiments can accelerate the discovery of relevant materials. Past work has focused on complex multicomponent alloys in which it is difficult to pinpoint the effect of each component. On the other hand, in this work, Fe–Cu binary alloys were used as a model materials system to determine the feasibility of novel materials discovery through a rapid determination of multiple properties. The microstructures, magnetic, electrical, and mechanical properties of Fe–Cu alloys were rapidly determined. With increasing Cu content in Fe-xCu from 0 to 40 wt.%, the phases present changed from single phase BCC to a two-phase FCC + BCC microstructure. There was a decline in the saturation magnetization (Ms) from 211.3 to 118 emu/g. The hardness value increased from 166.3 HV to 238.5 HV, the coercivity (Hc) ranged from 14.6 to 45.7 Oe, and the resistivity varied between 27.3 and 43.0 μΩ·cm. The increased content of a Cu-rich phase led to a decrease in Ms and grain size, and higher Hc and hardness. Using an accelerated methodology, a significant variation in material properties was determined. Three compositions, i.e., Fe–3Cu, Fe–4Cu and Fe–10Cu, with a good balance of properties were identified for potential use in energy applications.

Ternary Mg-Sc-based TRIP alloys: Design strategy based on Sc-equivalent

This study addresses the transformation-induced plasticity (TRIP) effect observed in bcc single-phase Mg–Sc alloys, aiming to circumvent the strength-ductility tradeoff inherent in traditional Mg-based alloys. Introducing a third element (X = Zn, Y, Nd, Gd) significantly enhanced the strength of the binary Mg–Sc TRIP alloys, simultaneously preserving ductility due to the TRIP effect. Consequently, a ternary Mg–Sc–X TRIP alloy with a bcc single-phase, for instance, achieved an ultimate tensile strength of approximately 380 MPa and a fracture elongation of around 41%, surpassing the conventional tradeoff. Furthermore, we introduce the design strategy of Sc-equivalent (Sceq) to articulate the combined influence of Sc and X elements on the stability of the bcc phase. This novel approach demonstrates the room-temperature deformation behavior of the Mg–Sc–X ternary alloy can be predicted and modulated, showcasing superelasticity (17.5 < Sceq < 19.5) and TRIP effect (19.0 < Sceq < 21.0).

Advanced wear protection at high temperatures: A study of Al20V20Cr20Nb(40-x)Mox RHEA coatings on Ti6Al4V by laser cladding

Al20V20Cr20Nb(40-x)Mox Refractory High Entropy Alloys (RHEAs) coatings were applied to Ti6Al4V surfaces via laser cladding. These coatings, primarily in a single BCC phase with dendritic microstructures, demonstrated varied wear resistance. Notably, the Al20V20Cr20Nb10Mo30 exhibited the highest wear resistance, achieving a wear rate reduction of 98.35 % and 99.28 % compared to uncoated Ti6Al4V and the Al20V20Cr20Nb30Mo10 coating, respectively. This superior performance is attributed to the formation of a dense oxide film and the beneficial presence of rod-like Al2(MoO4)3 and Cr2(MoO4)3 oxides, which enhance mechanical clamping at the surface. The study highlights the critical role of rapid oxide film formation at 600 °C in enhancing the high-temperature wear resistance of Ti6Al4V, offering insights into the tribological behaviour of RHEA coatings under extreme conditions.

Phase evolution, mechanical properties, and corrosion resistance of Ti2NbVAl0.3Zrx lightweight refractory high-entropy alloys

Herein, a series of Ti2NbVAl0.3Zrx (x = 0.25, 0.5, 0.75, 1) light refractory high entropy alloys were designed and prepared based on the concept of B2 ordering and solid solution strengthening. The Zr0.25, Zr0.5, and Zr0.75 alloys exhibited a disordered BCC + ordered B2 duplex structure, while the Zr1 alloy displayed a BCC single-phase structure. The addition of Zr hinders the formation of B2 ordering, transforming the alloy from a BCC + B2 duplex structure to a BCC single-phase structure. The Zr0.75 alloy has a yield strength of 1022 MPa and a tensile strain of ∼9.4 %. Furthermore, electrochemical tests were conducted in 3.5 wt% NaCl solution revealed that the Ti2NbVAl0.3Zrx LRHEAs showed high resistance to pitting corrosion. Incorporating the Zr element enhanced the polarization resistance and reduced the corrosion rate; however, excessive Zr content led to a shift in micro-galvanic corrosion from the nanoscale to the microscale, resulting in pitting corrosion. The passivation film compositions of the four alloys formed at a potential of 0.7 VSCE were analyzed by X-ray photoelectron spectroscopy, and their corrosion resistance in a chlorine-containing environment was examined in depth.

Microstructures and Corrosion Behaviors of Non-Equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox)(x = 0, 0.23) High-Entropy Alloy Coatings Prepared by the High-Velocity Oxygen Fuel Method

The non-equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox) (x = 0, 0.23) high-entropy alloy (HEA) coatings were prepared by the high-velocity oxygen fuel (HVOF) method. The microstructures and corrosion behaviors of the HVOF-prepared coatings were investigated. The corrosion behaviors were characterized by polarization, EIS and Mott-Schottky tests under a 3.5 wt.% sodium chloride aqueous solution open to air at room temperature. The Al0.32CrFeTi0.73Ni1.50 coating is a simple BCC single-phase solid solution structure compared with the corresponding poly-phase composite bulk. The structure of the Al0.32CrFeTi0.73Ni1.27Mo0.23 coating, combined with the introduction of the Mo element, means that the (Cr,Mo)-rich sigma phase precipitates out of the BCC solid solution matrix phase, thus forming Cr-depleted regions around the sigma phases. The solid solution of large atomic-size Mo element causes the lattice expansion of the BCC solid solution matrix phase. Micro-hole and micro-crack defects are formed on the surface of both coatings. The growth of both coatings’ passivation films is spontaneous. Both passivation films are stable and Cr2O3-rich, P-type, single-layer structures. The Al0.32CrFeTi0.73Ni1.50 coating has better corrosion resistance and much less pitting susceptibility than the corresponding bulk. The corrosion type of the Mo-free coating is mainly pitting, occurring in the coating’s surface defects. The Al0.32CrFeTi0.73Ni1.27Mo0.23 coating with the introduction of Mo element increases pitting susceptibility and deteriorates corrosion resistance compared with the Mo-free Al0.32CrFeTi0.73Ni1.50 coating. The corrosion type of the Mo-bearing coating is mainly pitting, occurring in the coating’s surface defects and Cr-depleted regions.

A novel Nb–TiNb nanocomposite with single-phase BCC structure for bio-implant applications

A novel Nb–TiNb nanocomposite with single-phase BCC structure for bio-implant applications

The Influence of Bias Voltage on the Structure and Properties of TiZrNbMo Coating Deposited by Magnetron Sputtering

TiZrNbMo coatings have been deposited using the direct current pulsed magnetron sputtering method in an argon atmosphere. The synthesis processes have been conducted under various process parameters. The structure (chemical and phase composition) and mechanical properties of the obtained multicomponent coatings are investigated as a function of plasma modulation frequency (10 Hz and 1000 Hz) and substrate bias (0 to −150 V). It is the case that an increase in the substrate bias decreases the deposition rate and alters the coating’s chemical composition. The latter leads to a Ti concentration decrease and a simultaneous increase in Mo and Nb concentrations in the final coating material. X-ray diffraction measurements indicate a single-phase BCC structure, with grain size decreasing as substrate bias increases. This ultimately forms an amorphous–nanocrystalline structure at −150 V. The mechanical properties of the multicomponent TiZrNbMo coatings have been determined using the nanoindentation method. The maximum values of hardness (13.45 GPa) and elastic modulus (188.6 GPa) are achieved at a substrate bias of −150 V. We also show that the minimum elastic modulus (41.8 GPa) is achieved at an intermediate substrate bias of −100 V.

Effect of Heat Treatment on Mechanical Properties and Corrosion Response of HVOF Sprayed High Entropy Alloy Coatings

Surface and sub-surface related degradation of steels can be minimized using suitable surface coatings. High entropy alloys (HEA) are prominent and emerging materials among many coating materials. The current study investigates the effect of heat treatment of HEA coating on mechanical, metallurgical, and corrosion properties. The HEA coatings on SS304 steel were deposited using a High-Velocity Oxy-Fuel (HVOF) thermal spray process. The developed coatings were furnace heat treated at 700 °C, 900 °C, and 1100 °C, respectively, and their performance was benchmarked with the as-sprayed coatings. The metallurgical, mechanical, and microstructural analyses were performed using X-ray diffraction (XRD), Nanoindentation, Scratch test, and Field Emission Scanning Electron Microscope (FESEM) techniques. The corrosion response of the as sprayed and heat-treated coatings were recorded using a Potentiostat. The results indicated that as-sprayed coatings consisted of a single-phase BCC solid solution; however, the single-phase changed to a dual dual-phase system after heat treatment (BCC+FCC). The 900 °C heat-treated HEA coating exhibited superior mechanical and corrosion properties. But those characteristics started diminishing when the heat treatment temperature exceeded 900 °C. The introduction of the new FCC phase softened the coating, thereby leading to the evolution of microcracks in the coating. These micro-cracks acted as channels for electrolyte diffusion and further corroded the coatings. The current study surmised that HVOF-sprayed HEA coating should not be heat treated at above 900 °C.

Simulation of ordering and diffusion in CrxMoNbTaVW alloys within the framework of the N-body approach when specifying interatomic interactions

Purpose. Development of interatomic potentials for atomistic simulation of alloys based on refractory metals of the V-Cr-Nb-Mo-Ta-W system and atomistic simulation using these ordering and diffusion potentials in CrxMoNbTaVW alloys. Methods. The development of the interatomic potentials of the V-Cr-Nb-Mo-Ta-W system was carried out within the framework of the 𝑁-body approach; To optimize the parameters of the potentials, the results of calculations within the framework of the electron density functional theory using the VASP software package were used as target values; the simulations of ordering and diffusion was carried out using methods of molecular dynamics and the developed We have previously used the combined method of molecular dynamics and the Monte Carlo method (MD+MK). Results. Within the framework of the 𝑁-body approach, potentials are constructed that complement the V-Nb-Mo-W potential system that we built earlier to the V-Cr-Nb-Mo-Ta-W system. The constructed potentials predict the characteristics of alloys in good agreement with experimental data, CALPHAD data and density functional theory data. Using these potentials by the MD+MC method, CrxMoNbTaVW alloys were modeled, where 𝑥 = 0, 0.5, 1, 2 and 3, in the temperature range from 500 ºC to 2300 ºC. The MD+MC calculations and CALPHAD data agreed in the temperature and concentration regions containing one phase of BCC. At a temperature of 1000ºC, MD + MC calculations show the presence of a single BCC phase, which contradicts CALPHAD data, but is consistent with experimental data. The simulation showed that the atomic structure of the CrMoNbTaVW model alloy is self-sufficient to realize the diffusion of components without artificial introduction of vacancies. The absolute values of the diffusion coefficients of the components and the values of the effective activation energy of diffusion in a solid solution of CrMoNbTaVW were calculated for the first time by the method of molecular dynamics. Analysis of the calculated diffusion characteristics indicates that a diffusion mechanism is implemented in the CrMoNbTaVW alloy, which includes coordinated movement of atoms of various grades. Conclusion. The development of methods for atomistic simulations of alloys based on refractory metals of the V-Cr-Nb-Mo-Ta-W system and the results of atomistic simulation of ordering and diffusion in CrxMoNbTaVW alloys have shown their importance for explaining and predicting heat resistance caused by diffusion processes in multicomponent alloys at high temperatures.

Microstructural, Electrochemical, and Hot Corrosion Analysis of CoCrFeCuTi High Entropy Alloy Reinforced Titanium Matrix Composites synthesized by Microwave Sintering

CoCrFeCuTi High Entropy Alloy (HEA) is reinforced in Ti6Al6V2Sn alloy through microwave sintering-assisted powder metallurgy and its corrosion behaviour is investigated under different conditions. The ball-milled CoCrFeCuTi HEA powder exhibits 17 μm average particle size of irregular fragments with a single-phase BCC structure and is added as reinforcement in Ti alloy at 3, 6, 9, and 12 wt%. As more reinforcement is added, the α-Ti decreases and β-Ti increases which enhances the interfacial bonding. The pinning effects from reinforcements inhibit grain growth contributing to improved properties including higher relative density with less porosity. The 12 wt% composite showed remarkable microhardness of 734 HV which is increased by 43.8% over Ti alloy. The 12 wt% composite also achieved finer grains (0.345 μm) due to uniform internal heat generation from the process. Corrosion behaviour is assessed through electrochemical corrosion and hot corrosion analysis, with 12 wt% composite demonstrating 59.5% better corrosion resistance compared to Ti alloy. The induced corrosion products, formation of passivation films, and their mechanism are examined by morphological analysis.

Compositional effect on microstructure and mechanical properties of AlNbTiZr-based refractory high entropy alloys

This study aims to investigate the phase composition, microstructure, and mechanical properties of three refractory high-entropy alloys (RHEAs): Al7(NbTiZr)93, Al7(NbTiZrMo)93, and Al7(NbTiZrTa)93. The as-cast Al7(NbTiZr)93 alloy exhibits a single-phase BCC structure, with a yield strength (YS) of 1050 MPa at room temperature. The addition of Mo and Ta leads to the formation of Al7(NbTiZrMo)93 and Al7(NbTiZrTa)93 alloys with BCC-B2 and B2-FCC dual-phase structures, whose YS values reach 1741 MPa and 2350 MPa, respectively. At 800 °C, trace amounts of ordered B2 phase are generated in the Al7(NbTiZr)93 matrix, and the YS decreases from 1050 MPa at room temperature to 219 MPa at 800 °C. In the Al7(NbTiZrMo)93 alloy, the 10 nm B2 precipitates grow to several hundred nanometers, and the YS decreases to 431 MPa after compression at 800 °C. In the Al7(NbTiZrTa)93 alloy, the grid B2-FCC structure at room temperature transforms into a disordered BCC structure at 800 °C, yet possessing the YS of 908 MPa and demonstrating acceptable ductility. Moreover, Ta exhibits the better structural and performance matching than Mo in AlNbTiZr-based RHEAs. Therefore, it opens up new prospects for regulating the structure and high-temperature performance of AlNbTiZr-based RHEAs.

Liquidus surface projection and isothermal section at 1500 °C of (Mo-5Nb)-Ti-C pseudo-ternary system

The liquidus surface projection and isothermal section at 1500 °C of the (Mo-5Nb)-Ti-C pseudo-ternary system were experimentally determined. X-ray diffraction analysis and scanning electron microscopy in conjunction with electron-probe microanalysis were carried out to analyze the solidification behavior and phase constituents. The replacement of 5 at.% Mo with Nb was found to negligibly affect the solidification path or the formation of new phases. However, the quasi-peritectic point U2 shifted closer to the (Mo-5Nb)-C border in the liquidus surface projection than in the Mo-Ti-C system. The BCC single-phase region, BCC + TiC two-phase region, and BCC + Mo2C + TiC three-phase region were determined in the isothermal section at 1500 °C. The replacement of 5 at.% Mo with Nb was found to expand the BCC + TiC two-phase region and narrow the BCC + Mo2C + TiC three-phase region by stabilizing the TiC phase. Therefore, the addition of Nb to the Mo-Ti-C system expanded the compositional range of the BCC + TiC two-phase region, leading to variable properties of TiC-dispersed BCC-based alloys and BCC-TiC cermets.