Reinforced Titanium Matrix Research Articles

Effect of temperature on microstructure and mechanical properties of ECAPed (TiB + La2O3)/Ti-6Al-4V composites

TiB short fibers and La2O3 particles reinforced titanium matrix composites (TMCs) were successfully equal-channel angular pressed (ECAPed) at 600 °C–900 °C. The effect of ECAP temperature on the microstructure and mechanical properties of the TMCs was investigated. The results indicated that dislocation tangling formed cell structures in matrix at lower ECAP temperature. In contrast, continuous dynamic recrystallization occurred at higher ECAP temperature, and promoted the formation of numerous new ultrafine grains. The average aspect ratio of TiB short fibers decreased with increasing ECAP temperature, which induced interfacial debonding. The tensile strength of TMCs ECAPed at 800 °C was up to 1128 MPa, which was 18% higher than the as-received composites. Interfacial debonding led TiB short fibers in low aspect ratios disabled to bear load, while the formation of ultrafine grains increased the strength of TMCs. The coupling of these two factors resulted in little effect of ECAP temperature on the tensile strength. However, the elongation of ECAPed TMCs generally decreased due to the loss of strain hardening capacity. Stress concentration tended to occur around the tips of TiB short fibers due to the interfacial debonding and cause crack propagation. It led to the premature fracture and low ductility.

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.

Characterization of ceramic reinforced titanium matrix composites fabricated by spark plasma sintering for anti-ballistic applications

Titanium has found extensive use in various engineering applications due to its attractive physical, mechanical, and chemical characteristics. However, titanium has relatively low hardness for use as an armour material. ZrB2 was incorporated to the Ti matrix to form a Ti-based binary composites. In this study, powder metallurgy techniques were employed to disperse the ceramic particulates throughout the matrix material then consolidated through spark plasma sintering. The composites were densified at 1300 °C, pressure of 50 MPa, and holding time of 5 min. The microstructure and phase analysis of the sintered composites was carried out using SEM and XRD, while the hardness was determined using Vickers' microhardness tester. The SEM and XRD results confirmed the presence of the TiB whiskers which renowned with the improving the hardness of titanium. The hardness of the composite with 10 wt% ZrB2 showed the highest hardness compared to that obtained for the 5 and 15 wt% ZrB2 composites which was 495 and 571Hv respectively.

Reconstruction and refinement of TiB whiskers in titanium matrix composite after electron beam remelting

The size and distribution of TiB whiskers (TiBw) in TiB reinforced titanium matrix composite (TiB-TMCs) were tailored by the electron beam remelting. A significant refinement of TiBw has been achieved in the remelted region, as well as the grain. Interestingly, the refined TiBw were reconstructed via electron beam remelting, forming the quasi-continuous network (QCN) structure and dispersive structure along the depth direction of the remelted region. A gradient hardness is obtain in the remelted TMCs, and the wear resistance is greatly improved after remelting. This study provides a promising method to tailor the architecture of TiBw in the TiB-TMCs for enhancing the surface performance.

The influence of interface reaction zone on interfacial fracture toughness of SiC fiber reinforced titanium matrix composites

A fiber-reaction zone-matrix three-phase model is developed to evaluate the interfacial fracture toughness of titanium alloys reinforced by SiC monofilaments. Based on fracture mechanics, theoretical equations of GIIc are presented, and the effects of several key factors such as crack length and the interface reaction zone thickness on the critical applied stress necessary for crack growth and interfacial fracture toughness are discussed. Finally, the interfacial fracture toughness of typical composites including Sigma1240/Ti-6Al-4V, SCS-6/Ti-6Al-4V, SCS-6/Timetal 834, SCS-6/Timetal 21s, SCS-6/Ti-24Al-11Nb and SCS-6/Ti-15V-3Cr are predicted by the model. The results show that the model can reliably predict the interfacial fracture toughness of the titanium matrix composites.

Dry sliding wear characteristics of in-situ TiBw/Ti6Al4V composites with different network parameters

Abstract Ceramics reinforced titanium matrix composites (TMCs) exhibited high specific strength especially with a special network architecture. This study investigated wear characteristics of the novel TMCs with different parameters, the results show that in-situ TiBw enhances hardness and resists abrasion effectively. Meanwhile, the mechanism varied from micro-cutting to brittle debonding with increasing TiBw content, and increasing network size caused the increase of COF and wear loss. Consequently, the composite with 8.5 vol.% TiBw and network size of 60 μm exhibited the best wear properties. Moreover, the subsequent heat treatment further enhanced the abrasion resistance by transformed β phase coexisted with network structure, which resulted in decrease of COF from 0.251 to 0.149 and reduced wear loss by 19.7%.

Investigation on microstructure, mechanical and tribological properties of in-situ (TiB + TiC)/Ti composite during the electron beam surface melting

The (TiB + TiC)/Ti composite was successfully in-situ synthesized by the electron beam surface melting. The supplied energy input has significant effect on the microstructure evolution and properties of the titanium matrix composites (TMCs). Some aggregations of TiB whiskers around un/semi reacted B4C particles appeared in the TMCs with low energy input, resulting in the deterioration of mechanical performances, especially the wear resistance. The B4C powders fully interact with Ti matrix when the energy input increases. However, TiB whiskers, the in-situ reaction product, grow and coarsen when the energy input continuously increases, which deteriorates the mechanical and tribological properties of the TMCs. The energy input is thereby optimized to be 3.2 J/mm in order to obtain the fine in-situ reinforcements without the un/semi melted B4C particles, exhibiting the highest hardness, elastic modulus and wear resistance. This study unravels the microstructure controlling methods during the electron beam surface melting process and the optimization mechanism of the mechanical and tribological properties, which is of significance for the application of the in-situ ceramics reinforced titanium matrix composites. Overall, the results indicate that the input energy should be controlled to avoid the presence of un/semi reacted B4C and coarse TiB whiskers for the electron beam surface melted TMCs with superior properties.

Grinding performance of TiCp/Ti-6Al-4V composites with CBN wheels, part I: experimental investigation and surface features

This article presents a comparison study on the machining performance of particulate reinforced titanium matrix composites (PTMCs) in conventional speed grinding (CSG) and high speed grinding (HSG) using monolayer brazed CBN wheels. Grinding forces, temperature and ground surface topology have been analyzed. It is discovered that the grinding forces in CSG are higher than those in HSG. However, grinding temperature in HSG is higher. Grinding scratches and concavities are the dominant ground surface features in both the CSG and HSG. The machined surface obtained in HSG is smoother than that obtained in CSG. The material removal mechanism of PTMCs include ductile removal regime of the metallic matrix and brittle removal regime of the TiC reinforced particles in grinding.

Study on Mechanical Alloying of TiB<sub>2</sub> Particulate Reinforced Titanium Matrix Composites

TiB2 particulate reinforced titanium matrix composites were prepared by mechanical alloying and spark plasma sintering. Volume fraction of TiB2 powders in the composites are 5%, 10%, 15%. The effect of milling time and the volume fraction of reinforcement on microstructure and properties of the composites were studied. The results show that with increasing milling time, the size of powder particles decreases, quantity of them increases, and microstructure of the sintered samples becomes finer and more uniform. When milling time reaches 30h, the trend of powder agglomeration increases, the downward trend of the particle size becomes slowly. With the milling time, the density of titanium matrix composites is on the rise. The density of 10vol%TiB2 particulate reinforced titanium matrix composites can reach 4.799 g/cm3, with 30h milling time and sintering at 900°C. The density and hardness of the composites increase with increasing the volume fraction of TiB2. When the volume fraction of TiB2 is 15%, after milling 10h and sintered at 800°C, the density and hardness of the composites can reach 4.713g/cm3 and HV851.58.

Grinding performance of TiCp/Ti-6Al-4V composites with CBN wheels, part II: material removal behavior based on FEM

In order to understand the material removal behavior of TiCp/Ti-6Al-4V particulate reinforced titanium matrix composites (PTMCs) during conventional speed grinding (CSG) and high speed grinding (HSG), a 3D finite element (FE) model has been established. Based on the FE model, the material removal behavior and the influence of grinding speed on the formation of machined surface feature were discussed. The results show that the material removal behavior in grinding of PTMCs can be divided into ductile regime removal of the metal matrix materials and brittle regime removal of the TiC reinforced particles. The ductile regime removal is dominated by serrated chip formation. The brittle regime removal is dominated by brittle fracture, crack initiation, crack propagation. The grinding speed has a considerable influence on the ground surface features. The ground surface morphology obtained in CSG is more complex and poorer than that obtained in HSG.

Comparison between axial residual stresses measured by Raman spectroscopy and X-ray diffraction in SiC fiber reinforced titanium matrix composite

Accurate measurement and analysis of residual stress state in the SiCf/Ti composites are crucial to optimizing their fabrication process and to understanding their failure mode, but they are still a challenge. In this work, SiCf/C/Ti17 composites with~48% fiber volume fraction, consisting of W-core SiC fibers (~100 m in diameter), turbostratic C coating (~2.5 m in thickness) and Ti17 matrix, are prepared by consolidating precursor wires fabricated by matrix-coated fiber method through hot isostatic pressing at 920℃/120 MPa/2 h; these samples are used for measuring their stresses. It is noted that turbostratic C coating, a necessary diffusion barrier layer between SiC fiber and Ti17 alloy matrix, bears the residual stress caused by the mismatch of thermal expansion coefficients between fiber and matrix during consolidation. It is found that the graphene planes are almost parallel to the axial direction of SiC fibers in the turbostratic C coating revealed by high magnification transmission electron microscope, and thus G peak position of C coating would be sensitive to stress state. Accordingly, micro-Raman spectroscopy is first used to measure the G peak positions of C coating under stress and stress-free state in the SiCf/C/Ti17 composite, respectively. Based on the position shift of G band caused by residual stress, the axial residual compressive stress of SiC fiber in SiCf/C/Ti17 composite is calculated to be~705.0 MPa. For comparison, X-ray diffraction method is also adopted to measure the interplanar spacing values of the Ti17 alloy matrix in different directions to obtain the spatial strains. During measurement, -Ti (213) high-angle diffraction peak is chosen to reduce test error, and then the different interplanar spacing values of -Ti (213) are obtained by varying the values of in three different directions at =0, 45 and 90. As three-axis-stress model is employed, the residual tensile stress of Ti17 alloy matrix in the axial direction of SiCf/C/Ti17 composite is~701.3 MPa, which is transformed through linear elastic theory into the residual compressive stress of SiC fiber of~759.4 MPa. The similar results confirm that it is reliable to characterize the residual stress in the SiCf/C/Ti17 composite with high-texture turbostratic carbon by both the Raman spectroscopy and the X-ray diffraction method.

Effect of TiC content on Sliding Wear Behavior of TiC-Ti Metal Matrix Composite

In this study, investigations have been conducted on the influence of percentage of TiC on the wear behavior of TiC reinforced titanium matrix composite (TiC-Ti) prepared by conventional powder metallurgy method. The four different type of composite with varying percentages of TiC (30, 40, 50 and 60%) have been considered for the sliding ball-on-disc type wear test. The wear value was measured in terms of weight loss of the composite pellets after the wear test using a high precision weighing balance. In addition, the dimension (depth and width) of the wear tracks were also measured using a stylus surface profilometer and the wear depth and width were correlated with the wear value measured through weight loss. The experiment results revealed that percentage of TiC has significant influence on the wear behavior of TiC-Ti composite.

Microstructure and mechanical properties of Ti-15Mo-xTiC composites fabricated by in-situ reactive sintering and hot swaging

TiC reinforced titanium matrix composites are promising for advanced applications. Generally, the relative density of the composites and the interfacial bonding between the matrix and reinforced particles may have a great influence on the mechanical properties. This study presented the fabrication of the full-densified Ti-15Mo-xTiC (x = 1.5, 3.0, 4.5 wt%) composites through in-situ reactive sintering of Ti, Mo, and MoC powders and hot swaging process. Experimental results show the formation of TiC and the absence of MoC in the fabricated composites. After hot swaging, the TiC particles showed aligned distribution along the swaging direction, and exhibited well bonding with the β-Ti matrix. Increasing the TiC content leads to increase tensile strength and Young's modulus but decrease elongation. Ti-15Mo-4.5TiC offers and outstanding combination: ultimate tensile strength = 1290 MPa, yield strength = 1075 MPa, Young's modulus = 89 GPa, and tensile elongation = 3.1%. The strengthening effect is attributed to Mo solid solution in Ti matrix, β-Ti grain refinement, and TiC particle reinforcement. The specific contribution of each mechanism is quantitatively calculated, showing good agreement with the experimental data.

Interfacial Fracture Toughness of Fiber Reinforced Titanium Matrix Composites by Push out Test

Abstract The model for single fiber push-out test was developed to evaluate the fracture toughness GIIc of the fiber/matrix interface in titanium alloys reinforced by SiC monofilaments. Theoretical solution to GIIc was obtained from fracture mechanics, and the effects of several key factors such as the applied stress needed for crack advance, crack length, and interfacial frictional shear stress were discussed. The predictions by the model were compared with the previous finite element analysis results for the interfacial toughness of the composites including Sigma1240/Ti-6-4, SCS/Ti-6-4, SCS/Timetal 834 and SCS/Timetal 21s. The results show that the model can reliably predict the interfacial toughness of the titanium matrix composites, in which interfacial debonding usually occurs at the bottom of the samples.

Laser engineered net shaping of quasi-continuous network microstructural TiB reinforced titanium matrix bulk composites: Microstructure and wear performance

Titanium (Ti) and its alloys have been successfully applied to the aeronautical and biomedical industries. However, their poor tribological properties restrict their fields of applications under severe wear conditions. Facing to these challenges, this study investigated TiB reinforced Ti matrix composites (TiB-TMCs), fabricated by in-situ laser engineered net shaping (LENS) process, through analyzing parts quality, microstructure formation mechanisms, microstructure characterizations, and workpiece wear performance. At high B content areas (original B particle locations), reaction between Ti and B particles took place, generating flower-like microstructure. At low B content areas, eutectic TiB nanofibers contacted with each other with the formation of crosslinking microstructure. The crosslinking microstructural TiB aggregated and connected at the boundaries of Ti grains, forming a three-dimensional quasi-continuous network microstructure. The results show that compared with commercially pure Ti bulk parts, the TiB-TMCs exhibited superior wear performance (i.e. indentation wear resistance and friction wear resistance) due to the present of TiB reinforcement and the innovative microstructures formed inside TiB-TMCs. In addition, the qualities of the fabricated parts were improved with fewer interior defects by optimizing laser power, thus rendering better wear performance.

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.

Materials removal mechanism in high-speed grinding of particulate reinforced titanium matrix composites

A finite element (FE) model was established for high-speed grinding of particulate reinforced titanium matrix composites (PTMCs). The materials removal mechanism, including the grinding force and resultant stress, the removal behavior of alloy matrix and reinforcing particles, have been analyzed. Particularly, the effect of grinding parameters on the surface defects was discussed. The results indicate that, the grinding force has different characteristics when the alloy matrix and reinforcing particle were removed, respectively, and the grinding force fluctuates significantly in the removal process of reinforcing particle. The material removal can be divided into four stages: plastic removal of the alloy matrix, crack initiation in reinforced particles, crack propagation in reinforced particles, brittle failure of reinforced particles. Under the current grinding conditions, compared with the grinding speed, the undeformed chip thickness has greater influence on the formation of machined surface defects. The simulation results agreed well with experiment.

Spark plasma consolidation of continuous fiber reinforced titanium matrix composites

An attempt was made to produce continuous fiber reinforced titanium matrix composites using spark plasma sintering machine from foils and fibers. The materials used were metastable beta titanium alloy Ti-15V-3Cr-3Al-3Sn foils (125µm thick) and silicon carbide fibers (100µm in diameter). The method involved consolidating foils with fibers placed in between them at regular intervals. After a series of trials, the feasibility of the process was established. Spark plasma consolidation enabled satisfactory foil bonding and fiber embedment at a significantly lower temperature and time compared to conventional diffusion bonding or vacuum hot pressing. The composite samples consolidated above the beta-transus temperature of the titanium alloy were found to develop satisfactory strengthening precipitation upon direct aging. The current study shows that spark plasma consolidation is an excellent alternative to conventional diffusion bonding for producing continuous fiber reinforced titanium matrix composites.

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.

Rapid in-situ reaction synthesis of novel TiC and carbon nanotubes reinforced titanium matrix composites

In-situ TiC and remained multi-walled carbon nanotubes (MWCNTs) reinforced Ti composites were synthesized using vacuum hot-press sintering and hot rolling. The effect of weight fraction of MWCNTs on microstructural evolution and mechanical properties of the Ti composites was investigated. The results indicated that both proportion and particle size of TiC increased in proportion to MWCNTs content, which resulted in different matrix microstructure, and the grains were obviously refined after rolling deformation. The hardness tests indicated that MWCNTs addition could make the composites harden, and 18.4% improvement in hardness was obtained after hot rolling. The significant improvement in both strength and hardness could be attributed to grain refinement, solid solution strengthening of carbon and dispersion strengthening of TiC particles and remained MWCNTs. A good combination of strength and ductility were achieved in Ti–1wt% MWCNTs composites, which were in accordance with the uniform distribution of smaller-sized TiC particles in Ti matrix.