Ti Solid Solution Research Articles

Multicomponent binders for PcBN performance enhancement in cutting tool applications

This study proposes a novel design of binders for polycrystalline cubic boron nitride (PcBN) cutting tool materials. Well-known binder phases TiC and TiN were combined with transitional metal nitrides ZrN, VN, and HfN. Performance screenings of longitudinal turning Inconel 718 and AISI 316 L highlighted the superior performance of PcBN materials with mixed TiC-ZrN and TiC-VN binders. These two systems were further sintered in a wider range of temperatures. XRD and STEM-XEDS analysis confirmed mutual dissolution of both TiC and ZrN, and TiC and VN, thus forming two types of solid solutions (Ti,Zr)(C,N) and (Ti,V)(C,N). Extended performance tests showed that tools with TiC-ZrN binder outperform reference PcBN with TiC binder by up to 20% when machining Inconel 718. When machining hardened Caldie tool steel, the performance of tools with TiC-ZrN and TiC-VN binders were 80–90% higher than the reference tools.

Atomic diffusion mechanism and interface nanomechanics in the Al/Ti composite structures

In this work, Al/Ti composite structures are obtained by isothermal compression at 550 °C and then annealed at 500–650 °C, respectively. The microstructure, elemental diffusion behavior , bonding characteristic and nanomechanics at the Al/Ti interface are systematically investigated by different material characterization methods. A nanoscale Al–Ti solid solution is formed at the contact interface between AA6063 and Ti–6Al–4V sheet, and TiAl 3 is generated after annealing. Si-enriched clusters at the Ti/TiAl 3 interface and Mg-enriched clusters at the Al/TiAl 3 interface are observed, which retards the growth of the TiAl 3 layer. With an increase in the annealing temperature, the average thickness of the TiAl 3 layer dramatically increases and the enrichment of Si and Mg decreases. Ordered TiAl 3 is gradually formed through the atomic rearrangement in the Ti–Al–Si–V structures at the three-dimensional Ti/TiAl 3 interface, accompanied by the transformation of an order–disorder–order structure. The nanomechanics at the interface is closely related to the annealing temperature, elemental diffusion and microstructure characteristic, which is also discussed. • Si-enriched and Mg-enriched clusters are observed at the Al/Ti interface, which retards the growth of TiAl 3 . • With an increase in temperature, the thickness of the TiAl 3 layer increases and the enrichment of Si and Mg decreases. • TiAl 3 is formed by the atomic rearrangement in Ti–Al–Si–V structures and the transformation of a disorder–order structure. • Differences of the nanomechanics at the interface cause the deformation incompatibility and interfacial debonding.

Pressureless sintering of HfB2-based ceramics as control rod materials: Synergistic effects of the sintering additive and solid solution

The effects of sintering additives (Boron and SiC) and solid solution (TiB2) on the densification of HfB2-based ceramics, processed by pressureless sintering, were investigated for potential applications as advanced control rod materials. The addition of B was found to improve the densification properties of HfB2 through removal of the oxygen contamination yet incurred unfavourable grain growth. SiC was able to further enhance the densification through a grain pinning effort, improving the microstructure. In combination with oxygen impurity removal by the addition of B, the solid solution of Ti into HfB2 contributed to further improving the densification by reducing the particle size of HfB2 powder, further promoting diffusion during sintering. The grain size of SiC phase was also reduced through the refinement of HfB2 powder via solid solution. The deployment of B and SiC sintering additives, alongside TiB2 solid solution, during pressureless sintering was found to be beneficial in the preparation of high density HfB2-based ceramics, increasing microstructure density and enhancing mechanical properties.

Interfacial behaviour of the high-entropy alloy CuCoCrFeNi and TC4 joint obtained by vacuum diffusion welding

In this work, good bonding between the high-entropy alloy (HEA) CuCoCrFeNi and TC4 titanium alloy was obtained through vacuum diffusion welding at a joining temperature of 1000 °C for 60 min under a pressure of 5 MPa. The results showed that the typical interfacial microstructure of the CuCoCrFeNi/TC4 joint was TC4/diffusion layer/island structure/dendritic structure/diffusion layer/HEA. Compared with Ti atoms, atoms such as Cr and Co from the CuCoCrFeNi substrate were prone to diffuse into the other material. Intermetallic compounds Cu0.5Fe0.5Ti and Co0.15Ni0.85Ti, solid solutions Ti(Fe, Cr)ss and amorphous materials were produced in the joint. The self-diffusion activation energy formula [see formula in PDF] can be used to approximate the order of diffusion capacity of elements, which follows in Cr >Fe> Co > Ni.

Micro-addition of Fe in highly alloyed Cu-Ti alloys to improve both formability and strength

Cu-Be alloys provide excellent electrical and mechanical properties, but present serious health hazards during manufacturing. Among alternative alloys, the Cu-Ti system has the highest yield strength; however, Ti cannot be easily solutionized at concentrations above 4 wt%, resulting in a relatively low formability. In this study, Cu-xTi-yFe (x = 3, 5, 6 wt% and y = 0, 0.3 wt%) alloys were studied after both solution-annealing and age-hardening through mechanical testing and microstructure analysis. Micro-additions of Fe kept high concentration of Ti in solid solution (up to 6 wt%) after water quenching and suppressed the classical “wave-like” early-stage precipitation. Instead, a new dispersion of nano precipitates was observed. This behavior results in doubling the ductility in the solution annealed state (up to 48% elongation), together with maintaining a very high strength after ageing (up to 975 MPa) from precipitation of metastable nano α-Cu4Ti. This study shows that Fe micro-additions, when combined with a higher amounts of Ti (6 wt%), enables the production of Cu-based alloys combining high formability and strength, providing an excellent alternative to Cu-Be in mechanical applications.

Effects of processing parameters on densification behavior, microstructure evolution and mechanical properties of W–Ti alloy fabricated by laser powder bed fusion

Tungsten and its alloys have been widely used in various industries such as nuclear energy, medical shielding, rocket nozzle. However, the intrinsic high melting point and high ductile-to-brittle transition temperature (DBTT) normally limit their further applications. In this work, the transition element Ti modified W alloy was processed by laser powder bed fusion (LPBF) additive manufacturing process with different laser processing parameters. The densification behavior, microstructure evolution, and mechanical performance of LPBF-processed W–Ti samples were systematically investigated through the optimization of laser processing parameters. It indicated that the highest relative density of 99.1% without obvious pores and balling phenomenon were obtained at the applied energy density of 848 J/mm3 with laser power of 350 W and scan speed of 275 mm/s. The typical microstructure of LPBF-processed W–Ti alloy could be divided into two main regions including W bulk region and W dendrite region with the chemical compositions of W–Ti solid solution, which was caused by the significant difference of melting point between W and Ti. The high microhardness of 731 HV0.2 and compressive performance (σbc = 1719 MPa, δ = 24.7%) were achieved. Compared with pure tungsten samples of our previous work (902 MPa), the compressive strength of W–Ti alloy by LPBF displayed significant improvement of 90%, which could be attributed to the increased densification level and solid solution strengthening mechanism. These findings provided the knowledge of the relationship between laser processing parameters and properties of LPBF-processed W–Ti alloy, further providing reference values applicable for development of W-based alloys by laser additive manufacturing.

Microstructure, Microhardness, Fracture Toughness, and Abrasive Wear of In-Situ Synthesized TiC/Ti-Al Composite Coatings by Cold Spraying Combined with Heat Treatment

TiAl intermetallic compounds, as a new kind of high-performance light-weight structural material, are widely applied in many fields. Titanium carbide (TiC) as the reinforcing phase could improve the mechanical properties, wear resistance, and heat-resistance stability of TiAl intermetallic compounds. Ti(Al, C) mixture powders were deposited by cold spraying at gas temperature of 250 °C, 450 °C, and 550 °C. Then, Ti(Al, C) coatings were annealed at temperatures of 650 °C for different times and following holding at 1100 °C for 3 h. The microstructure, microhardness, fracture toughness, and abrasive wear of Ti-Al composite coatings were investigated. The research results were that the particle size of mixture powders decreased as the ball milling time prolonging. Ti(Al) solid solution appeared in the mixture powders as the milling time increased to 30 h. The average porosity of the coating sprayed at 550 °C was the lowest (0.85%). The as-sprayed coatings exhibited the same phase compositions with the mixture powders. The coating sprayed at gas temperature of 550 °C has the highest microhardness and the lowest weight loss. Ti-Al intermetallic was in-situ synthesized after annealing at 650 °C. The average porosity of the annealed coating (sprayed at 450 °C) was the lowest. The content of Ti-Al intermetallic compounds of the annealed coating sprayed at 450 °C is the highest. The X-ray diffraction (XRD) analysis results are consistent with the EDS analysis of the annealed coatings after annealing at 650 °C. Ti-Al intermetallic compounds were almost completely formed in the three kinds of the coatings after annealing at 650 °C for 20 h and following holding at 1100 °C for 3 h. TiAl and TiAl3 intermetallic phases were in-situ synthesized in the coatings based on the energy dispersive spectroscopy (EDS) and XRD analysis. TiC was also in situ synthesized in the coatings as the annealing temperature increased to 1100 °C. The annealed coating (sprayed at 450 °C) has the highest microhardness, fracture toughness, and wear resistance properties after annealing at 1100 °C for 3 h.

Textural and Geochemical Evidence for Magnetite Production upon Antigorite Breakdown During Subduction

AbstractMagnetite stability in ultramafic systems undergoing subduction plays a major role in controlling redox states of the fluids liberated upon dehydration reactions, as well as of residual rocks. Despite their relevance for the evaluation of the redox conditions, the systematics and geochemistry of oxide minerals have remained poorly constrained in subducted ultramafic rocks. Here, we present a detailed petrological and geochemical study of magnetite in hydrous ultramafic rocks from Cerro del Almirez (Spain). Our results indicate that prograde to peak magnetite, ilmenite–hematite solid solution minerals, and sulfides coexist in both antigorite-serpentinite and chlorite-harzburgite at c. 670 °C and 1·6 GPa, displaying successive crystallization stages, each characterized by specific mineral compositions. In antigorite-serpentinite, magnetite inherited from seafloor hydration and recrystallized during subduction has moderate Cr (Cr2O3 < 10 wt%) and low Al and V concentrations. In chlorite-harzburgite, polygonal magnetite is in textural equilibrium with olivine, orthopyroxene, chlorite, pentlandite, and ilmenite–hematite solid solution minerals. The Cr2O3 contents of this magnetite are up to 19 wt%, higher than any magnetite data obtained for antigorite-serpentinite, along with higher Al and V, derived from antigorite breakdown, and lower Mn concentrations. This polygonal magnetite displays conspicuous core to rim zoning as recognized on elemental maps. Cr–V–Al–Fe3+ mass-balance calculations, assuming conservative behavior of total Fe3+ and Al, were employed to model magnetite compositions and modes in the partially dehydrated product chlorite-harzburgite starting from antigorite-serpentinite, as well as in the serpentinite protolith starting from the chlorite-harzburgite. The model results disagree with measured Cr and V compositions in magnetite from antigorite-serpentinites and chlorite-harzburgites. This indicates that these two rock types had different initial bulk compositions and thus cannot be directly compared. Our mass-balance analysis also reveals that new magnetite formation is required across the antigorite-breakdown reaction to account for the mass conservation of fluid-immobile elements such as Cr–V–Al–Fe3+. Complete recrystallization and formation of new magnetite in equilibrium with peak olivine (Mg# 89–91), chlorite (Mg# ∼95), orthopyroxene (Mg# 90–91), and pentlandite buffer the released fluid to redox conditions of ∼1 log unit above the quartz–fayalite–magnetite buffer. This is consistent with the observation that the Fe–Ti solid solution minerals (hemo-ilmenite and ilmeno-hematite) crystallized as homogeneous phases and exsolved upon exhumation and cooling. We conclude that antigorite-dehydration reaction fluids carry only a moderate redox budget and therefore may not be the only reason why the magmas are comparatively oxidized.

Development of core–shell-structured Ti-(N) powders for additive manufacturing and comparison of tensile properties of the additively manufactured and spark-plasma-sintered Ti-N alloys

In this study, Ti-(N) powders with a core–shell structure were prepared via a nitriding process of titanium (Ti) powders for metal additive manufacturing (AM). Nitriding of spherical Ti powders (D50=130 µm and D50=63 µm) was carried out at different temperatures from 873 K to 1373 K for 10 min. The nitriding process enabled the manufacture of a core–shell-structured Ti-(N) powder, where an N-enriched shell surrounds a lower N core. The thickness of the N-rich Ti shell increases exponentially with increasing nitriding temperature. Depending on nitriding temperature, a shell layer consisting of Ti2N and TiN compounds can form. Based on X-ray diffraction (XRD) results, it was identified that the N-rich shell is composed of (i) only Ti(N) solid solution when nitrided below 1023 K; and (ii) Ti(N) solid solution, Ti2N and TiN compounds if nitrided at or above 1023 K. The core–shell-structured Ti-(N) powders were subsequently used to manufacture bulk samples by spark plasma sintering (SPS) and laser metal deposition (LMD) processes for comparison. The microstructure was characterized and discussed. LMD-fabricated Ti-N alloy samples exhibited high tensile strength (965 MPa) with good tensile ductility (7.6%) due to the homogeneous distribution of N and fine grain size. In contrast, SPS-fabricated Ti-N alloy samples using the same nitrided Ti-N powder showed much lower tensile strength (708 MPa) with essentially no tensile ductility (0.3%) due to the inhomogeneous distribution of N. LMD can allow the fabrication of strong and ductile Ti-N alloys while it is not possible by SPS.

Microstructure and Mechanical Properties of Spark Plasma Sintered Nanocrystalline TiAl-xB Composites (0.0 <x<1.5 at.%) Containing Carbon Nanotubes

This paper investigates the effects of minor additions of carbon nanotubes (CNTs) and boron on the structure and mechanical properties of nanocrystalline TiAl intermetallic compound. Nanocrystalline TiAl-xB(0.0 < x < 1.5 at.%) composites containing 1 wt.% CNT were synthesized by mechanical alloying and spark plasma sintering. Microstructure and mechanical properties of samples were evaluated using a scanning electron microscopy, energy-dispersive x-ray spectroscopy, elemental mapping, differential scanning calorimetry, Vickers hardness measurement, and shear–punch test. The findings of the current study show that milling up to 40 h results in the formation of Ti(Al) solid solution. Further milling up to 60 h is associated with a complete amorphization of the structure. Results also show that spark plasma sintering leads to the transformation of Ti(Al) solid solution into a mixture of Ti3Al, Ti2Al, and TiAl intermetallic compounds. Minor additions of boron and CNTs cause a significant grain refinement. The addition of the latter significantly improves the elongation as well. The implications of boron/CNT additions for the microstructure of TiAl and how it correlates with the mechanical properties are thoroughly discussed in this paper.

Powder Composition Structurization of the Ti-25Al-25Nb (at.%) System upon Mechanical Activation and Subsequent Spark Plasma Sintering

The results of a study of the microstructure evolution of pre-mechanically activated elementary powders based on the Ti-25Al-25Nb (at.%) compositions differing in the particle size of the aluminum (Al) component are presented. It was found that during the mechanical activation, most of the Al was dissolved in the Ti and Nb lattices by interpenetration with the formation of solid solutions (Ti, Al) and (Nb, Al). It has been established that an increase in temperature to 1400 °C, when sintering powder materials based on the Ti-Al-Nb system, leads to a sharp increase in the temperature of Al particles, as a result of the melting of which it is impossible to control the phase formation, which ultimately leads to the difficulty of obtaining the required product. It was determined that in the process of spark-plasma sintering of mechanically activated compositions, intermetallic compounds are formed based on phases ‒ α2, B2 and O, and with an increase in the sintering temperature, their morphology and distribution in the alloy volume change.

A Novel Approach by Spark Plasma Sintering to the Improvement of Mechanical Properties of Titanium Carbonitride-Reinforced Alumina Ceramics.

Ti(C,N)-reinforced alumina-zirconia composites with different ratios of C to N in titanium carbonitride solid solutions, such as Ti(C0.3,N0.7) (C:N = 30:70) and Ti(C0.5,N0.5) (C:N = 50:50), were tested to improve their mechanical properties. Spark plasma sintering (SPS) with temperatures ranging from 1600 °C to 1675 °C and pressureless sintering (PS) with a higher temperature of 1720 °C were used to compare results. The following mechanical and physical properties were determined: Vickers hardness, Young’s modulus, apparent density, wear resistance, and fracture toughness. A composite with the addition of Ti(C0.5,N0.5)n nanopowder exhibited the highest Vickers hardness of over 19.0 GPa, and its fracture toughness was at 5.0 Mpa·m1/2. A composite with the Ti(C0.3,N0.7) phase was found to have lower values of Vickers hardness (by about 10%), friction coefficient, and specific wear rate of disc (Wsd) compared to the composite with the addition of Ti(C0.5,N0.5). The Vickers hardness values slightly decreased (from 5% to 10%) with increasing sintering temperature. The mechanical properties of the samples sintered using PS were lower than those of the samples that were spark plasma sintered. This research on alumina–zirconia composites with different ratios of C to N in titanium carbonitride solid solution Ti(C,N), sintered using an unconventional SPS method, reveals the effect of C/N ratios on improving mechanical properties of tested composites. X-ray analysis of the phase composition and an observation of the microstructure was carried out.

Evolution of microstructure and interfacial characteristics of complete solid-solution Ti(C,N)-based cermets fabricated by mechanical activation and subsequent in situ carbothermal reduction

Complete solid-solution Ti(C,N)-based cermet, with no typical core-rim structure, was synthesized through mechanical activation and subsequent in situ carbothermal reduction method. XRD, SEM, TEM, and C/N analysis were used to investigate the microstructure, phase transformation, and the interfacial characteristics of the present cermets. During solid-state sintering, the (Ti,Mo)C/(Ti,Mo)(C,N) phases formed through the transformation of Mo-based solid solution which generated by mechanical activation. Then, the formed (Ti,Mo)C/(Ti,Mo)(C,N) continuously dissolved into the nickel-based binder above 1100 °C. It was found that in the subsequent stage of liquid sintering, the mechanical activation and also the presence of extremely fine TiC/Ti(C,N) particles accelerated the Mo diffusion into the hard phase, resulting in a large quantity of (Ti,Mo)(C,N) solid solutions formed in the nickel-based binder. Finally, complete (Ti,Mo)(C,N) solid-solution phase was obtained via dissolution and re-precipitation. The higher toughness and transverse rupture strength (TRS) of the synthesized new cermet, as compared with traditional cermets, were mainly caused by the increased crack deflection and transgranular fracture of the novel cermets. Moreover, the interface among the Ni-based binder phase and complete solid solution hard phase exhibited a semi-coherency state with high-density dislocations, which also significantly improved the TRS and toughness of the synthesized cermets.

Microstructural evolution during spark plasma sintering of TiC–AlN–graphene ceramics

This examination intended to evaluate the synergic influence of graphene nano-platelets (GNPs) and AlN on the microstructure and consolidation behavior of TiC. The spark plasma sintering (SPS) method was employed as the manufacturing process under the sintering circumstances of 40 MPa, 10 min, and 1900 °C. The simultaneous incorporation of AlN and GNPs could improve the relative density of TiC more than 4%, reaching a fully dense ceramic. According to the X-ray diffraction (XRD) spectrum, thermodynamic study, as well as the microstructural assessments, i.e., scanning electron microscopy (SEM), Electron probe micro-analyzer (EPMA), scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM), the TiN and Al2OC ingredients were produced over the SPS process as the in-situ phases. Although Al2OC remained in the microstructure as an amorphous-like phase, the in-situ produced TiN dissolved into the TiC matrix, creating a Ti(C,N) solid solution. A chemical reaction between AlN and the surface oxide of TiC, namely TiO2, was found to be responsible for the in-situ generation of the TiN compound. Thanks to the formation of the solid solution, strong interfaces were created amongst the matrix grains, promoting the transgranular fracture mode. Moreover, some dislocations and distorted atomic planes were seen in the microstructure, derived from the thermal expansion coefficients' inconsistency between the different phases over the cooling stage.

Plasma-Spark Sintering of Oxide–Non-Oxide Components with the Addition of a TiC–ZrC Solid Solution and Various Metal Powder Mixtures

The effects of powder mixtures of W–Mo and Zr–Ti combined with sintered solid solution TiC–ZrC during spark plasma sintering of compositions at a pressing load of 60 MPa in the range 1200 – 1600°C on the phase composition, microstructure, grain sizes of crystalline phases, relative density, linear shrinkage, physical-mechanical properties, and linear correlation of elasticity modulus and fracture toughness of mullite–β-Si3N4–c-BN samples are shown in the present work. Synthesized powders of β-Si3N4 and c-BN are characterized by extensive crystallization of β-Si3N4 and c-BN. Solid solution TiC–ZrC sintered by a spark-plasma method at 1800°C shows roughly equal crystallization of (Zr,Ti)C and (Ti, Zr)C and a nonuniform and incompletely sintered crystalline microstructure. Samples with W–Mo and Zr–Ti mixtures sintered in the range 1200 – 1600°C show extensive mullitization; active crystallization of β-Si3N4, (Ti,Zr)C, solid solutions Mo, Wand W, Mo, and β-Zr,Ti; and lower crystallization of c-BN, (Zr,Ti)C, and β-Ti,Zr. The W–Mo mixture in the range 1400 – 1600°C favors the formation of a more uniformly and densely sintered microstructure of the ceramic phase; roughly round-shaped particles of solid solutions Mo, W and W, Mo in the metallic phase; more reinforced boundary areas of ceramic-metallic and metallic phases; and polydisperse grain compositions of crystalline phases. As a result, the composition with the W–Mo mixture sinters more uniformly and gradually in the range 1200 – 1600°C with the corresponding sample showing greater values of physical-mechanical properties, higher cracking resistance, and a greater linear correlation of the elasticity modulus and fracture toughness.

Microstructure and Photothermal Conversion Performance of Ti/(Mo-TiAlN)/(Mo-TiAlON)/Al2O3 Selective Absorbing Film for Non-Vacuum High-Temperature Applications

This paper aims to clarify the phase composition in each sub-layer of tandem absorber TiMoAlON film and verify its thermal stability. The deposited multilayer Ti/(Mo-TiAlN)/(Mo-TiAlON)/Al2O3 films include an infrared reflectance layer, light interference absorptive layers with different metal doping amounts, and an anti-reflectance layer. The layer thicknesses of Ti, Mo-TiAlN, Mo-TiAlON, and Al2O3 are 100, 300, 200, and 80 nm, respectively. Al content increases to 12 at.% and the ratio of N/O is nearly 0.1, which means nitride continuously changes to oxide. According to X-ray Diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results, the diffraction peak that appears at 2θ = 40° demonstrates that Mo element aggregates in the substitutional solid solution (Ti,Al)(O,N) columnar grain. TiMoAlON films have low reflectivity in the spectrum range of 300–900 nm. When Al content is more than 10 at.%, absorptivity is almost in the spectrum range from visible to infrared, but absorptivity decreases in the ultraviolet spectrum range. When Al content is increased to 12 at.%, absorptivity α decreases by 0.05 in the experimental conditions. After baking in atmosphere at 500 °C for 8 h, the film has the highest absorptivity when doped with 2 at.% Mo. In the visible-light range, α = 0.97, and in the whole ultraviolet-visible-light near-infrared spectrum range, α = 0.94, and emissivity ε = 0.02 at room temperature and ε = 0.10 at 500 °C.

Strengthening of solid solution (Ti,La)(C,N)-based cermets by LaB6 addition

(Ti,La)(C,N)-based solid solution cermets are fabricated from self-prepared (Ti,La)(C,N) carbonitrides by powder metallurgy with LaB6 addition in the solid solution. Based on the results of XRD and SEM analyses, it is confirmed that there is complete dissolution of (Ti,La)(C,N) powder. The presence of La can effectively suppress grain overgrowth and thus enhance the homogeneity of porcelain microstructure, consequently increasing the particle size of black phase. On the basis of equal mass fraction of La, the performance of (Ti,La)(C,N)-based cermets is better than that of Ti(C,N)-La-based cermets prepared by simple addition of LaB6 to Ti(C,N)-based cermet powder. The discrepancy can be directly related to the effect of adding LaB6 in the solid solution. The physical and mechanical properties of (Ti,La)(C,N)-based cermets comes to optimum when the content of dissolved La is 0.25 wt%, and there is hardness elevation of 20%. With suitable La addition, there is decrease of oxygen content in the solid solution of cermets. It is hence deduced that LaB6 can improve the performance of cermets as a deoxidizer.

Wetting Kinetics and Microstructure Analysis of BNi2 Filler Metal over Selective Laser Melted Ti-6Al-4V Substrate.

The wetting kinetics of nickel-based filler metal (BNi2) over selective laser-melted Ti-6Al-4V (SLMed TC4) titanium alloy in a protective argon atmosphere is experimentally investigated using a real-time in situ hot stage equipped with an optical microscope. The spreading processes at different temperatures are similar, and the overall wetting/spreading process can be roughly divided into three stages: (i) an initial stage, (ii) a rapid spreading stage, and (iii) an asymptotic stage. Moreover, the wetting kinetics of the BNi2/SLMed TC4 system can be expressed by empirical power exponential function Rn~t with n = ~1. In the process of spreading, Ti-based solid solution (Ti(ss)) and intermetallic compound (Ti2Ni and TiB2) were formed at the interface within the reaction domain, and the phase transition of α’ martensitic to α-Ti and β-Ti also took place. The influence of elevated temperature on the spreading and wetting kinetics of the BNi2/SLMed TC4 system was studied, and the results show that the increase of temperature has a slightly promoting effect on the spreading, but a limited impact on the value of n. In addition, the spreading and wetting kinetics of BNi2/SLMed TC4 system are similar to those of BNi2 on conventional forged TC4 substrate.

Microstructure and mechanical properties of WC and Ti(C0.7N0.3) modified NbC solid solution cermets

Eight NbC solution matrix cermets were prepared by liquid phase sintering of mixtures containing NbC, WC, Ti(C0.7N0.3), Mo2C, Co and Ni powders. The influence of the WC and Ti(C0.7N0.3) content on the microstructure and mechanical properties of the cermets was investigated. Microstructural investigation was supported by thermodynamic equilibrium calculations to predict the composition of the constituent phases as a function of WC content at 1420 °C. The results indicated the variation in WC and Ti(C0.7N0.3) content had a significant influence on the phase content, the in-situ formed (Nb,W,Ti,Mo) (C,N) solution grain growth and concomitant mechanical properties. The NbC solution cermets with 12–32 wt% WC were composed of a core-rim (Nb,W,Ti,Mo) (C,N) phase, Co–Ni alloy binder, and rimless Ti(C0.57N0.43) phase. XRD phase analysis and simulations revealed that the composition of the cubic structure (Nb,W,Ti,Mo) (C,N) and Ti(C,N) solid solutions depend on the WC content. The NbC matrix cermets with 12–32 wt% WC exhibited a Vickers hardness (HV30) of ∼1500 kg/mm2 and indentation toughness of ∼9 MPa m1/2.

Effect of titanium addition on structure, corrosion resistance and mechanical properties of aluminum coatings on NdFeB by ion-beam-assisted magnetron sputtering

Titanium has been added in the Al coatings on sintered NdFeB magnets by ion-beam-assisted magnetron sputtering to improve the mechanical properties of coatings without corrosion resistance deterioration. The effect of Ti addition on structure, mechanical and electrochemical properties of Al coatings has been investigated, complemented by x-ray diffraction and transmission electron microscopy. The results show that the ion-beam-assisted magnetron co-sputtering of Al and Ti obtains a single-phase polycrystalline structure of Al–Ti solid solution. With the increasing Ti content, the coating structure becomes denser and the grain size is reduced. Both the mechanical and wear properties of the coatings are improved with the addition of Ti where the hardness of the Al–Ti coating increases with the increasing amount of Ti. Polarization and EIS testing results show that the titanium-doped coatings have an enhanced corrosion resistance by comparison with pure Al coatings when Ti content is lower than 4.3 at.%.