TiB Reinforced Titanium Matrix Composites Research Articles

Pressure-driven structural transformation and lattice deformation in TiB reinforced titanium matrix composites: An in-situ synchrotron x-ray diffraction study

Understanding the mechanical responses of structural materials to extreme pressures has particular implication for not only their intrinsic solid properties, e.g., phase transformation, equation of state, lattice deformation, but also the mechanical engineering for extreme environments. In this work, the structural transformation of TiB reinforced Ti (Ti-TiBw) composite particles under hydrostatic, uniaxial and dynamic pressures has been comparatively investigated by diamond anvil cells combined with in-situ synchrotron x-ray diffraction. According to the variation of critical pressure of α → ω martensitic transformation, it is found that, under uniaxial pressure, the presence of nano-TiBw network could largely enhance structural resistance to deviatoric stress for the composites. A fit to the equation of state of Ti-TiBw composites under hydrostatic and uniaxial pressure yields the bulk modulus of ∼120 and ∼ 133 GPa, respectively, which increases 2.56% and 11.76% relative to pure Ti. Furthermore, the lattice deformation behaviors in Ti-TiBw composites and pure Ti during martensitic and its reversible transformation vary with pressure, deviatoric stress and compression rate. Due to the constraints by rigid TiBw network rather than “soft” grain boundary, the lattice deformation along the basal, prismatic, and pyramidal planes in Ti-TiBw system suggests an isotropic behavior, though the deviatoric strain of basal plane displays obvious dependence upon uniaxial pressure.

Formability, densification behavior and hierarchical grain structure of laser-directed energy deposition of TiB reinforced titanium matrix composites

Objective to obtain the homogeneous microstructure and the high strength-ductility has always been the significant considerations for the additively manufactured titanium alloys, but it is still limited to its huge columnar β grains (>1 mm). Designing equiaxed grain is still a critical method to overcome the challenge. This work successfully in-situ developed 5 vol% TiB reinforced titanium matrix composites (TMCs) with tailorable columnar to equiaxed grain transition (CET) and network structures through controlling laser energy densities (Ev) of the laser-directed energy deposition (L-DED) process. The deposited TMCs (230.8 J/mm3) showed the highest relative density of 97.683%. The sufficient Ev (∼250.0 J/mm3) induced the significant CET and the large hierarchical networks (41 μm). The 5 vol% TiB dramatically reduced the β grain size by over 150 μm, obtaining a refined grain size of 29.8–42.5 μm. TiB/α-Ti interfaces exhibited the favorable bonding and presented the uniform strain distribution without noticeable strain gradient. This work obtained the highest ultimate tensile strength of 1138 MPa (176.4 J/mm3) and remained an acceptable ductility. The good strength-ductility synergy was achieved at the Ev of 230.8 J/mm3 due to the high densification and the CET. The grain refinement was mainly responsible for the excellent strength of TMCs. The CET coupled with hierarchical coarsening networks were advantageous for improving ductility at high level of Ev (≥230.8 J/mm3). This study confirmed that changing solidification condition could further induce the significant CET for the additively manufactured TiB/Ti6Al4V composites.

Achieving strength-ductility combination and anisotropy elimination in additively manufactured TiB/Ti6Al4V by in-situ synthesized network architecture with fine grains

It is of significance, but still remains a key challenge to overcome the strength–ductility trade-off, and homogenize the mechanical performance of the additively manufactured titanium alloy. Here, we provided a new strategy of multi-scale architecture design to overcome this issue through in-situ synthesizing TiB-reinforced titanium matrix composites manufactured by laser-directed energy deposition (LDED). The β grains were remarkably refined from ∼200 μm to ∼70 μm and the aspect ratio of α-Ti reduced from ∼16.3 to ∼4.8 by planting TiB (≥2.5 vol%). The 2.5 vol%TiB/Ti6Al4V composite exhibited the significant transition of columnar to equiaxed grains and presented the multi-scale columnar and equiaxed network structure with favorable continuity, and achieved the good combination of strength (1153 MPa) and ductility (6.2%) thanks to the grain refinement and structure strengthening afforded by the network structure with different strain domains. The 5 vol%TiB/Ti6Al4V obtained the excellent ultimate tensile strength of 1174 MPa while maintaining good ductility. Both the apparent columnar to equiaxed grain transition which led to the reduction of the texture intensity and Schmid factor, and the special distribution of TiB with <010> texture along the building direction achieved the isotropic strength in 2.5 vol%TiB/Ti6Al4V composite.

Corrosion behavior of in situ-synthesized (TiC+TiB)/Ti composites by laser powder-bed fusion: Role of scan strategy

The in-situ TiC and TiB reinforced titanium matrix composites were fabricated by laser powder fusion (LPBF) of B4C/Ti powder mixture, and the influence of scan strategy on the microstructure morphologies and corrosion resistance in NaCl solution were also investigated. The experimental results reveal that anodic dissolution of titanium matrix is accelerated and thus facilitates the formation of the TiO2 passive layer on the surface of the LPBF-produced (TiC+TiB)/Ti composites owing to the in-situ TiC and TiB reinforcements acting as micro-cathode in NaCl aqueous solution. The island scan strategy tends to result in a net-shaped distribution of TiC and TiB reinforcements and pore defects, which causes the inhomogeneity of galvanic couples and resultant TiO2 passive layer. Fortunately, the scan strategies of XY+ 30° and XY+ 67° can alleviate the thermal accumulation and leads to the transformation of refinements distribution to radial-shaped arrangement, which favors for the homogeneity of galvanic couples and resultant TiO2 passive layer. Moreover, the scan strategy of XY+ 90° generates a refinement and increased volume fraction of reinforcements and micro-galvanic couples, which significantly facilitates the formation of a thicker and less-defective TiO2 passive layer, thus leading to better corrosion resistance with a larger value of Rf. Furthermore, the corrosion mechanism of LPBF-produced (TiC+TiB)/Ti composites has also been discussed in detail based on the Electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy results.

Configuration of new fiber-like structure driven high matching of strength-ductility in TiB reinforced titanium matrix composites

To fulfill the combination of high strength and ductility, configuration of novel fiber-like structural TiB reinforced titanium matrix composites was designed and successfully fabricated through series of powder metallurgy and hot working process. The influence of the fiber-like structure and microstructures on the mechanical response is investigated to clarify their strengthening and plasticizing mechanisms. Smaller equiaxed α-Ti grains generated in both the composites region and Ti region of the TiB/Ti composites. The new configuration improved the tensile strength from 573.5 MPa to 659.1 MPa while the ductility (24.4%) was comparable with that of pure Ti (23.5%). Besides, prismatic <a> slips with Schmid factors above 0.4 had higher distribution in both the composites region and Ti region of the TiB/Ti composites than pure Ti along the loading direction, suggesting the higher deformation ability of the TiB/Ti composites. Moreover, the loading-unloading-reloading (LUR) true stress-strain curves showed much higher back stress in fiber-like structural TiB/Ti composites compared with unreinforced Ti during deformation. The existence of the back stress increased the strain hardening rate when the true strain was above 0.05 and strengthened the Ti region, which was caused by deformation incompatible between the composites region and Ti region during tensile loading in the TiB/Ti composites. The higher mechanical response of the TiB/Ti composites is attributed to the introduction of TiB reinforcements with the new fiber-like structure, and the coupling effect of consequent grain refinement, load transferring effect, dislocation pinning effect of the fine TiB particles, back stress strengthening and the higher Schmid factors of prismatic<a> slips. • Novel fiber-like structure was designed to match the high strength and ductility in TMCs. • Configuration design of high strength composites without losing ductility by tailoring the spatial distribution of reinforcements. • The ductility of the composites was maintained for the higher Schmid factor values of prismatic<a> system and back stress. • Grain refinement, load transferring effect and back stress strengthening result to the strength improvement.

Microstructural characterization and mechanical properties of nano-scale/sub-micron TiB-reinforced titanium matrix composites fabricated by laser powder bed fusion

A B4C/Ti-6Al-4V(Ti64) composite powder containing a minor B4C content (0.2 wt%) was developed by a novel technique and was subjected to the laser powder bed fusion (L-PBF) process within a wide range of laser powers and scanning speeds to fabricate titanium matrix composite (TMC) parts. The relative density measurement results revealed the achievement of almost fully dense TMC parts. Compared to the Ti64 case, slightly higher Ev values were required in the TMC system to obtain the highest relative density. Microstructural characterization of the TMC parts revealed the formation of large columnar prior β grains containing in-situ formed nano-scale/sub-micron TiB needles homogeneously dispersed in a martensitic matrix. While having almost the same ductility, the fabricated TMC parts showed 25% and 8% higher nanohardness, compressive yield strength, respectively, and 12% lower wear rate than the Ti64 sample. The improved mechanical properties of the TMC were due to the contribution of several factors, including the incorporation of nano-scale/sub-micron TiB reinforcement, the refinement of the martensite α՛ laths, and the solid solution strengthening effects of carbon atoms. The contribution of TiB presence and solid solution strengthening was ~60% and ~40% in the overall yield strength enhancement of the TMC parts, respectively.

Dynamic recrystallization and silicide precipitation behavior of titanium matrix composites under different strains

In order to elucidate the microstructure evolution and silicide precipitation behavior during high-temperature deformation, TiB reinforced titanium matrix composites were subjected to isothermal hot compression at 950 °C, strain rate of 0.05 s−1 and employing different strains of 0.04, 0.40, 0.70 and 1.00. The results show that with the increase of strain, a decrease in the content, dynamic recrystallization of the α phase and the vertical distribution of TiB along the compression axis lead to stress stability. Meantime, continuous dynamic recrystallization reduces the orientation difference of the primary α phase, which weakens the texture strength of the matrix. The recrystallization mechanisms are strain-induced grain boundary migration and particle stimulated nucleation by TiB. The silicide of Ti6Si3 is mainly distributed at the interface of TiB and α phase. The precipitation of silicide is affected by element diffusion, and TiB whisker accelerates the precipitation behavior of silicide by hindering the movement of dislocations and providing nucleation particles.

Achieving near equiaxed α-Ti grains and significantly improved plasticity via heat treatment of TiB reinforced titanium matrix composite manufactured by selective laser melting

Abstract A facile heat treatment strategy suitable for TiB reinforced titanium matrix composites (TMCs) fabricated by selective laser melting (SLM) is proposed. The effects of boron modification and heat treatment on the microstructure and mechanical properties of the selective laser melted TMC samples were systematically investigated. The ultrafine ∼2 vol% TiB whiskers that formed in situ exhibited a much more homogeneous distribution in the matrix compared to that of conventionally processed composites containing similar volume fractions, further promoting the formation of fine equiaxed α-Ti grains throughout the matrix. An excellent combination of strength and fracture strain of 1428 MPa and 43.6%, respectively, was simultaneously achieved for the heat-treated TMC, in which the plasticity was improved by 126% over that of the as-fabricated composite (19.3%). This finding provides significant guidance for tailoring the microstructure in selective laser melted TMCs to achieve the desired mechanical properties.

Insights into the interfacial bonding strength of TiB/Ti: A first principles study

First-principles calculations are performed to study the strength and nature of interfacial bonding at TiB/Ti interfaces. Sixteen (100)TiB/(101¯0)α-Ti interface models considering different (100)TiB terminations and stacking sites are investigated to determine their influence on the interfacial bonding strength and thermodynamic stability. The L bridge-site-B1-termination interface exhibits the strongest interfacial bonding and the most stable structure, forming strong Ti–B polar covalent bonds and maintaining the same epitaxial stacking sequence as bulk TiB at the interface. Moreover, seven alloying elements commonly used in titanium alloys are investigated to tailor the interfacial bonding strength of TiB/Ti interfaces. The calculated results indicate that the alloying elements of V, Cr, and Mo form stronger chemical bonds with B atoms than with Ti and have the tendency to aggregate at the TiB/Ti interface region, while improving its interfacial bonding strength. The alloying elements of Al, Si, Zr, and Sn generate weaker chemical bonds with B atoms and preferentially aggregate at sites away from the TiB/Ti interface. This tends to maintain or even lower the interfacial bonding strength of the interface. The calculated results, especially for V, are in good agreement with previous experimental observations. It is believed that the calculated results can provide theoretical evidence to guide experimental designs and improve the interfacial and macromechanical properties of TiB-reinforced titanium matrix composites.

Wire-feed deposition TiB reinforced Ti composite coating: Formation mechanism and tribological properties

To enhance the surface hardness and anti-wear performance so as to extend the applications of titanium (Ti) and its alloys in wear environments, TiB reinforced titanium matrix composites coatings were synthesized by tungsten inert gas (TIG) wire-feed deposition (WF-D) utilizing Ti-TiB2 cored wire as feedstocks for the first time. The coating showed a macroscopically uniform distribution, consisting of two-scale TiB whiskers (TiBw). The hardness of the coating (415 HV0.3) was increased by 108% than that of Ti substrate (200 HV0.3), while the wear loss (23.64 mg) decreased by 52.8% compared with the Ti substrate (50.13 mg). The performance improvement is attributed to in-situ two-scale TiBw that enhance the hardness of the coating and increase the resistance to plastic deformation. This work provides a new horizon for preparing anti-wear titanium matrix composites coatings.

Laser deposition-additive manufacturing of TiB-Ti composites with novel three-dimensional quasi-continuous network microstructure: Effects on strengthening and toughening

Abstract Although TiB reinforced titanium matrix (TiB-Ti) composites exhibit superior wear resistance and strength, they still demonstrate severe problems resulted from lowered toughness and ductility, as compared with titanium and its alloys. To reduce these problems, this paper tailors a three-dimensional quasi-continuous network (3DQCN) microstructure within TiB-Ti composites by in-situ laser deposition-additive manufacturing process. Results show that the laser power has great impacts on the formation of 3DQCN microstructure and the 3DQCN microstructure is beneficial to both strengthening and toughening effects on TiB-Ti composites. To have a quantitative understanding of strengthening effects, this paper, for the first time, has modeled the yield strength of TiB-Ti composites with 3DQCN microstructure.

Laser deposition-additive manufacturing of in situ TiB reinforced titanium matrix composites: TiB growth and part performance

Ceramic reinforced Ti matrix composites (TMCs) have been widely used under severe friction and heavy loading conditions due to their superior properties. Among different types of ceramic reinforcements, TiB is considered as one of the most suitable ceramic reinforcement materials for TMCs because of its high strength and stiffness, excellent interfacial bonding with Ti matrix, and low induced stress. As a laser additive manufacturing process, laser deposition-additive manufacturing (LD-AM) has been successfully utilized to fabricate Ti-based materials. However, investigations on LD-AM of in situ TiB reinforced TMCs are limited. This investigation, for the first time, reports the tomography analysis of TiB reinforcement within Ti matrix and the formation of novel flower-like microstructure. The influences of reaction energy on part performance have been explored. In addition, the effects of input fabrication variables (including laser power and Z-axis increment) on part performance (including density, microhardness, and compressive properties) have been investigated, providing guidance on selection of input fabrication variables for future research.

In-situ ultrafine three-dimensional quasi-continuous network microstructural TiB reinforced titanium matrix composites fabrication using laser engineered net shaping

In this study, we created an innovative ultrafine three-dimensional quasi-continuous network (3DQCN) microstructure by in-situ laser engineered net shaping (LENS) of TiB reinforced titanium matrix composites (TiB-TMCs). As a rapid solidification process, the LENS process enabled high degree of Ti grain refinement. The in-situ processed eutectic TiB aggregated at these Ti grain boundaries, forming the ultrafine 3DQCN microstructure. The microstructural characterizations of the ultrafine 3DQCN microstructure were investigated. Effects of the TiB reinforcement and the ultrafine 3DQCN microstructure on the mechanical performance of the fabricated parts were studied. The results demonstrated that the TiB-TMCs with the ultrafine 3DQCN microstructure exhibited superior mechanical properties.

Efffect of Spark Plasma Sintering Temperature on Mechanical Properties of &lt;i&gt;In Situ&lt;/i&gt; TiB/Ti Composites

The in-situ synthesized TiB reinforced titanium matrix composites have been prepared by spark plasma sintering technique at 950–1250°C, using mixtures of 10wt% TiB2 and 90wt% Ti powders. The effects of the sintering temperature on the mechanical properties (Vickers microhardness, yield strength and Young`s modulus) of the composites were investigated. SEM was used to analyze the reaction process and the microstructure of the compacts synthesized at different sintering temperatures. The results indicated that the in situ synthesized TiB grow rapidly with increasing sintering temperature. The composite sintered at 1250°C have the highest relative density of 99.2%. However, the composite sintered at 950°C exhibits the best Vickers microhardness of 4.64GPa and yield strength of 989MPa, respectively.

Microstructure of &lt;i&gt;In Situ&lt;/i&gt; TiB Reinforced Titanium Matrix Composite Coatings by Laser Cladding with Different Pre-Placed Powder Thickness

In situ reaction synthesized TiB reinforced titanium matrix composites were fabricated using rapid non-equilibrium synthesis techniques of laser cladding. Titanium matrix composite were laser cladding treated on Ti-6Al-4V using Ti and B powder mixture, and the designed weight fractions of B were 10 wt.% in the starting powder mixture. The composite coating mainly consists of α-Ti and TiB. The reinforcement TiB is dispersed homogeneously in the composite coating with pre-placed powder thickness of 0.5mm. The influence of pre-placed powder thickness on microstructure of laser cladding coatings was discussed.

Microstructures and mechanical properties of the in situ TiB–Ti metal–matrix composites synthesized by spark plasma sintering process

In situ synthesized TiB reinforced titanium matrix composites have been synthesized by spark plasma sintering (SPS) process at 950–1250 °C, using mixtures of 15 wt% TiB 2 and 85 wt% Ti powders. The effects of the sintering temperature on densification behavior and mechanical properties of the TiB–Ti composites were investigated. The results indicated that with rising sintering temperatures, relative densities of the composites increase obviously, while the in situ TiB whiskers grow rapidly. As a result, bending strength of the TiB–Ti composites increases slowly at the combined actions of the factors referred above. Fracture toughness of the composites is improved remarkably due to the large volume fraction of Ti matrix, the crack deflection, pull-out and the micro-fracture of the needle-shaped TiB grains. The results also suggested that TiB–Ti composite sintered at 1250 °C by SPS process exhibits the highest relative density of 99.6% along with bending strength of 1161 MPa and fracture toughness of 13.5 MPa m 1/2.

Microstructure and Wear Resistance of the Composite Coatings Fabricated on Titanium Alloys by Laser Cladding

In situ reaction synthesized TiB reinforced titanium matrix composites were fabricated using rapid non-equilibrium synthesis techniques of laser cladding. TiB/Ti composite coating was treated on Ti-6Al-4V surface using Ti and B powder mixture by laser cladding. Microstructure and dry sliding wear behavior of the in situ synthesized TiB/Ti composite coatings were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), energy-dispersive spectroscopy (EDS), hardness tester and friction and wear tester. The composite coatings consist of Ti, TiB and intermetallic compounds. The TiB reinforcement dispersed homogeneously in the composite coatings. The wear tests show that the friction coefficient and wear weight loss ratio of the coatings is lower than that of the Ti-6Al-4V alloy. The composite coating was reinforced by the in situ synthesized TiB ceramic particles. Based on the SEM observation, effects of scan speed on hardness and wear resistance of the laser cladding coatings were investigated and discussed.

In Situ TiB Reinforced Titanium Metal Matrix Composites Prepared by Spark Plasma Sintering

In situ synthesized TiB reinforced titanium matrix composites of Ti-B and Ti-TiB2 systems have been prepared by spark plasma sintering at 800-1200 °C under 20 MPa for 5 min. The effects of sintering temperature and reinforcement volume fraction on flexural strength, Young’s modulus and fracture toughness of the composites were investigated. The in situ synthesized TiB reinforcements are randomly and uniformly distributed in titanium matrix. The TiB whiskers are aligned along [010] direction, and the crystallographic planes of the TiB needles are always of the type (100), (101) and (10 1) . The parallel TiB were observed in β-Ti grains in both of the investigated composites. The in situ TiB needle is likely to grow along [010] direction which is parallel to [111] direction of cubic lattice of β-Ti phase.

Spark plasma sintering reaction synthesized TiB reinforced titanium matrix composites

Abstract The in situ TiB particle reinforced titanium metal matrix composites were prepared using MA followed by park plasma sintering (SPS) with a heating rate of 50 °C/min. The in situ TiB were synthesized by chemical reaction between TiB2 and Ti during the SPS process. The microstructure of the composites sintered at 800, 1000 and 1200 °C were investigated. TiB whiskers are needle-shape and uniformly dispersed in the titanium matrix. The interface between the in situ TiB needles and the titanium matrix is singular and faceted. The composite sintered at 1000 °C has a maximum value of relative density of 99.6%, and good mechanical properties with a flexural strength of 1007 MPa, Young's modulus of 146 GPa and fracture toughness of 8.64 MPa·m1/2, respectively. The fractographs of all composites exhibit a predominantly brittle cleavage fracture mechanism. The elastic modulus of synthesized TiB was estimated.

Microstructure and mechanical properties of in situ TiB reinforced titanium matrix composites based on Ti–FeMo–B prepared by spark plasma sintering

The in situ synthesized TiB reinforced titanium matrix composites have been prepared by spark plasma sintering at 800–1200 °C under 20 MPa for 5 min. The effects of sintering temperature and reinforcement volume fraction on flexural strength, Young’s modulus and fracture toughness of the composites are investigated. The titanium matrix consists of α-Ti and β-Ti phases, and the volume fraction of β-Ti increases with increasing sintering temperatures. The in situ synthesized TiB reinforcements are distributed randomly and uniformly in matrix. The transverse section of TiB has a hexagonal shape aligned along [0 1 0] direction, and the crystallographic planes of the TiB needles are always of the type ( 1 0 0 ) , ( 1 0 1 ) and ( 1 0 1 ¯ ) . The 10 vol% TiB reinforced composite sintered at 1000 °C exhibits excellent mechanical properties. The flexural strength, Young’s modulus and fracture toughness of this composite are 1560 MPa, 137 GPa and 8.64 MPa · m 1/2, respectively.