TC4 Matrix Research Articles

Effect of aging temperature on microstructure and mechanical properties of (Ti1400+TiC)/Ti6Al4V composites

Titanium matrix composites, due to their high strength, high modulus, and high temperature resistance, have become ideal materials that meet the lightweight and high-performance requirements in the aerospace industry. However, their poor ductility remains a key issue that restricts their widespread application. In this study, (Ti1400+TiC)/TC4 composites were prepared by low-energy ball milling and spark plasma sintering and subjected to solution treatment and aging treatment. The effects of aging temperature on the composition, microstructure, and mechanical properties of the composites were analyzed, and the strengthening mechanism of (Ti1400+TiC)/TC4 composites was discussed. The aging temperature between 350 ℃ and 700 ℃ had little effect on the microstructure of TC4 matrix and the discontinuous three-dimensional network structure of TiC particles. As the aging temperature increased, the elongated α-phase within the Ti1400 region became shorter and thicker, and Cr’s rapid diffusion resulted in β-phase being more widely distributed. After aging at 600 ℃, the tensile strength of the composite was 1202 MPa, and its total elongation reached 11.3 %, showing excellent strength-plasticity matching. The mechanical properties of composites are mainly affected by the microstructure in the Ti1400 region. The elongated α-phase in the Ti1400 region provides high strength for the composite. The thicker α-phase and the widely distributed β-phase led to more uniform strain within the composite, avoiding premature fracture caused by stress concentration near TiC particles and promoting ductility in the composite.

Microstructural Evolution and Deformation Mechanisms of In Situ TiC Reinforced Ti‐6Al‐4V Composites during High‐Temperature Hot Compression

Deformation processing is a key strategy to improve the strength‐ductility of metal matrixcomposites. Herein, TiC/TC4 composites are spark plasma sintered usingreinforcement precursors of reduced graphene oxide to reinforce TC4 matrix. Inorder to investigate the hot deformation behaviors and mechanisms of TiC/TC4 composites, the composites are hot compressed over temperature range of 870–1070 °C and strain range of 0.001–10 s−1. The results indicate that the optimal processing window of hot deformation ismainly within the temperature range of 890–970 °C and the strain rate range of 0.01–0.1 s−1. The flow instability of TiC/TC4 composites occurs in the temperature range of 890–930 and 1000–1060 °C at the strain rate range from 0.1 to 10 s−1. The thermal deformation mechanism of TiC/TC4 composites in the processingwindow region involves continuous dynamic recrystallization and discontinuous dynamic recrystallization. TiC can effectively hinder thedislocation motion, leading to the generation of high‐density dislocationsaround TiC. Consequently, this promotes sub‐grains formation and rotation,facilitating CDRX. Meanwhile, TiC particle induces high‐angle grain boundarymigration and provides more nucleation sites for recrystallized grains. These findings enhance understanding the role of hot deformation behaviors of Ti compositesand provide insights into their deformation processing.

In-situ synthesis of high-performance TiN/TC4 sandwich structures via nitrogen-controlled laser directed energy deposition

Laser Directed Energy Deposition (LDED) additive manufacturing offers a versatile approach for fabricating composite materials, encompassing a wide range of heterogeneous and transition materials, known for their exceptional mechanical properties. In this study, we focus on the synthesis of TiN/TC4 sandwich structural materials in atmospheres characterized by varying nitrogen-to-argon ratios. This study includes the in-situ synthesis, microstructural evolution, and mechanical characteristics of these TiN/TC4 sandwich structures during the LDED process. Through this process, TiN was formed in-situ by the interaction of Ti and N atoms, exhibiting in robust metallurgical bonding with the TC4 matrix. Notably, the microhardness of the TiN/TC4 sandwich structures exhibits periodic variations along the deposition direction, ranging between 314.4 HV0.2 and 661.5 HV0.2. The tensile strength of the TiN/TC4 sandwich structures experiences significant enhancement, while maintaining toughness due to the laminate structure and reinforced with ceramic particles inside. The resulting sandwich composites demonstrate outstanding ultimate tensile strength, which can achieve 1123.3 ± 29.7 MPa. This represents a notable improvement of 20.3% over the TC4 deposited in a pure Ar environment, with a corresponding plastic strain of 2.5 ± 1.7%. This study demonstrates that layered heterogeneous materials with superior mechanical strength can be synthesized in-situ through flexible integration of LDED process and reaction atmospheres.

Research on microstructure and mechanical properties of TC4/304 clad plates by asymmetric rolling with local strong stress

In order to solve the problems of complex traditional preparation process and low bonding strength of titanium/steel clad plates, TC4/304 clad plates were prepared by asymmetric rolling with local strong stress (ARLSS), the effect of rolling temperature on the interface bonding of clad plates was studied. The two-dimensional simulation model of TC4/304 clad plates rolling was established by finite element method, and its accuracy was verified by experiments. The experimental results show that the interfacial bonding strength of the clad plates increased with the increasing temperature, but when the temperature reached 950 °C, the brittle intermetallic compounds (IMCs) formed extremely fast, which greatly weakens the bonding strength. The clad plates showed the best bonding strength at 900 °C. After corrugated roll bonding (CRB) (33 % reduction ratio), the bonding strength at the peak was lower than that at the trough. After FRB (46 % reduction ratio), the interface bonding strength was slightly improved. The final peak bonding strength reached 519 MPa, and the trough bonding strength was 527 MPa. The improvement of bonding strength mainly came from the improvement of TC4 matrix strength. The finite element simulation results showed that multiple cross shear zone in the deformation zone of the CRB stage were beneficial to the bonding of dissimilar metals. While the deformation of the clad plates material in the FRB stage was consistent, which effectively avoided the cracking of the bonded area and further improved the bonding strength. Therefore, the strong non-uniform plastic deformation of ARLSS process had a significant effect on the deformation coordination of dissimilar metals and the quality improvement of clad plates.

Micron-sized SiC particles reinforced TC4 composites: Mechanical properties and strengthening mechanisms

SiC fiber, W fiber, C fiber and other continuous fiber-reinforced titanium matrix composites (TMCs) have limited their application prospects due to their anisotropy, interface reaction, and high costs. In contrast, the SiC particles (SiCp) reinforced TMCs are of particular interests due to their ease of fabrication, lower costs, and isotropic properties. Micron-sized SiCp reinforced TC4 (Ti-6Al-4V) composites (SiCp/TC4) were synthesized via spark plasma sintering (SPS). The microstructure and mechanical properties of SiCp/TC4 composites have been investigated. The results showed that SiCp/TC4 composites exhibite a typical Widmanstatten structure composed of plate α, grain boundary α phase, and intercrystalline β phase. TiC particles formed via the reaction of SiCp with the TC4 matrix distributed at grain boundaries. In the meanwhile, a small amount of Ti5Si3 have been observed around the β phase. The strength of the composites increased continuously with the increase of SiCp contents. Due to effects of grain refinement and load transfer strengthening and solution strengthening from C, O and Si elements, the composites of 0.5 wt% SiCp/TC4 has achieved a high yield strength and an ultimate tensile strength of 1053 MPa and 1144 Mpa, which are higher than TC4 matrix for 33.5% and 27.1%. SiCp/TC4 composites have widespread application prospects in aerospace, military and automotive industries.

Superior strength-ductility combination in TiC/TC4 composites via In situ construction Ti2Cu nanoparticles

Synergistic improvement of strength and ductility is challenging in the engineering applications of titanium matrix composites (TMCs). Herein, we fabricated the TC4 composites reinforced with grain boundary micron-TiC and intragranular nano-Ti2Cu using spark plasma sintering (SPS) and hot rolling (HR) to achieve a good balance between strength and ductility. An interfacial reaction between Ti and C forms the grain boundary TiC, and the vast majority of intragranular nano-Ti2Cu precipitates to accommodate the severe lattice distortion caused by the solid solution of Cu in β-Ti phase. Benefiting from Ti2Cu nanoprecipitates and their ability to effectively suppress dislocation motion, precipitation strengthening, and dislocation strengthening are the main factors, in addition to grain refinement strengthening due to deformation processing, that contribute to the realization of the superior yield strength (YS) of 1360 MPa and ultimate tensile strength (UTS) of 1504 MPa in composites than TC4 matrix (YS = 986 MPa, UTS = 1160 MPa). Meanwhile, the interfacial strain-delocalization effect of TiC/Ti2Cu with Ti matrix, the shear-lag effect of TiC, and the sustained strain-hardening effect provided by TiC/Ti2Cu empower the composites with an outstanding ductility (fracture elongation of 8.4 %). This study highlights the untapped potential for improving the mechanical properties of Ti matrix composites.

Constructing micro-network of Ti2Cu and in-situ formed TiC phases in titanium composites as new strategy for significantly enhancing strength

Titanium matrix composites (TMCs) with homogeneous microstructures often exhibit inferior mechanical properties including low strength and poor ductility, thus severely restricting their wide-range applications as engineering structural parts. Herein, we designed a hybrid structured (TiC + Ti2Cu)/TC4 composites consisting of TiC particles and micro-network structures of Ti2Cu, using reduced graphene oxides (rGO) and copper nano-powders as precursors via a two-step low energy ball milling and spark plasma sintering. These in-situ formed TiC particles were uniformly distributed within the TC4 matrix, whereas Ti2Cu nanoparticles were generated by the eutectoid reaction and distributed at the α/β phase interfaces, forming a micro-network structure within the titanium alloy matrix. Sizes, morphologies, distributions and fractions of Ti2Cu structures were adjusted by controlling the Cu contents, and these play dominant roles in determining tensile properties of the composites. The fabricated (TiC + Ti2Cu)/TC4 composites exhibit significantly higher tensile strengths than that of the monolithic TC4 (increased by 32.2 %), which is mainly attributed to the refinement strengthening from TiC + Ti2Cu hybrid reinforcements and precipitation strengthening from Ti2Cu with micro-network structures. This study develops a new methodology to significantly improve the tensile strength of carbonaceous nanomaterial reinforced titanium matrix composites.

Direct ink writing of high-performance multi-level interlocked laminate-network titanium matrix composites

ABSTRACT In this study, multi-level laminate-network boron nitride nanosheets (BNNSs)/TC4 composite with interlayer interlocking was fabricated using a facile direct ink writing (DIW) technique. In-situ 3D nano-configurations consisting of BNNSs and TiBx nanophases distributed around TC4 matrix particles formed the first-level network structure, while the above composite layers and TC4 layers with interlayer interlocking formed the second-level laminate structure. It exhibits a comparable high tensile strength of around 1203 MPa, compared to composites with a single-network structure, while demonstrating a 20% higher toughness of 55.8 MJ/m3. The interlayer interlocking microstructure interlayer could be responsible for the strength enhancement, which benefits the stress transfer between layers. The improved ductility could be attributed to the crack blocking adduced by the laminate structure and the 3D network in the composite layers.

Boron nitride nanosheets as precursors for 3D nano-configurations in titanium matrix composites: Interfacial evolution and mechanical behavior

Boron nitride nanosheets (BNNSs) have tremendous potential as reinforcements for titanium (Ti) due to their excellent strengthening and toughening efficiency from in-situ generated 3D nano-configurations. However, the effect of interfacial evolution on the mechanical properties of the BNNSs/Ti composite remains unexplored. To this end, in this study, the interfacial structure was regulated utilizing the time-dependent reaction of BNNSs/Ti system. Its effects on mechanical behavior were studied by combining experiments and molecular dynamic simulations. BNNSs were gradually converted to 3D nano-configurations over time and finally consumed to form coarsened TiB whiskers in the TC4 matrix. The composite with 3D nano-configurations exhibited a tensile strength of 1140.5 MPa and excellent toughness of 42.9 MJ/m3. Strength improvement stems primarily from nano-interlocking, which increases dislocation density under load and improves the interfacial shear strength. The considerable toughness results from the enhanced crack resistance brought by the 3D nano-configurations.

Influence of Bioactive Glass Addition on TC4 Laser Cladding Coatings: Microstructure and Electrochemical Properties

There is a growing interest in enhancing the bioactivity of TC4-based metallic biomaterials, which are known for their excellent biocompatibility. Bioactive glass (BG) has been recognized for its high potential in promoting bioactivity, particularly in osteo tissue engineering. This study focuses on investigating the influence of BG addition on the microstructure and electrochemical properties of TC4 coatings. The TC4/BG composite coatings were fabricated through laser cladding, and their microstructure was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical properties of the coatings were assessed through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in three different solutions. The results revealed that the incorporation of BG had a significant impact on the microstructure of the TC4 coatings, leading to the formation of a well-defined interface between the TC4 matrix and the BG aggregates. The distribution of BG aggregates within the TC4 matrix coating was found to be random and unrelated to the specific regions of the coating. The metallographic microstructure variations were attributed to different heat dissipation conditions during the laser cladding process. Furthermore, the electrochemical corrosion behavior of TC4/BG composite coatings reveals that they exhibit stability similar to that of passive films and good resistance against media corrosion compared to TC4, while also showing enhanced corrosion resistance in 3.5 wt% NaCl and Dulbecco’s modified Eagle medium (DMEM) solutions, indicating their potential for biomedical applications; however, the corrosion resistance decreases gradually in all solutions, potentially due to the elevated Cl− concentration. Further research can explore bioactivity enhancement of TC4/BG composite coatings and investigate the long-term stability and biological response of these coatings in diverse physiological environments.

Microstructure evolution, mechanical properties, and wear behavior of in-situ TiCx/TC4 composites

In this work, In-situ TiCx/TC4 composites were fabricated using Ti3AlC2 as a precursor via vacuum hot-pressing sintering. The effect of Ti3AlC2 content on the microstructure, mechanical properties, and wear behavior of TC4 matrix composites was investigated. The results indicate that the TiCx phase formed from the reaction between Ti3AlC2 and Ti during sintering. The in-situ formation of the TiCx phase could refine the size of the prior β grain and alter the microstructures of the matrix from the Widmanstatten structure of neat TC4 to an equiaxed structure. The TC4 matrix composites with different amounts of Ti3AlC2 exhibited higher hardness, yield strength, and tensile strength than neat TC4. When the volume fraction of Ti3AlC2 was 2.5%, the yield strength and tensile strength of composites were 951.2 MPa and 1033 MPa, respectively, which increased by 16.5% and 9.4% compared to neat TC4, respectively. Moreover, the elongation of the composites was 12.8% with substantially maintained plasticity. The improvement of yield strength in the composites is attributed to grain refinement strengthening and load transfer strengthening. The wear behavior of in-situ TiCx/TC4 composites was enhanced significantly. Abrasive wear and adhesive wear are the dominant wear mechanism in the TiCx/TC4 composites.

Heterogeneous network structures formed in TiC/TC4/β-Ti composites for enhancing strength with good ductility

Composites of TiC/(TC18 + TC4) with designed heterogeneous network structures were spark plasma sintered using reinforcement precursors of graphene and β-TC18 alloy to reinforce TC4 matrix. The heterogeneous networks of TiC/(TC18 + TC4) composites are typically mixed microstructures of α+β lamellar and equiaxed β phases. The synthesized composites exhibit superior high strength and ductility (i.e., with a fracture strength of 1150 MPa and a uniform elongation of 5%), compared with those of the sintered monolithic TC4 (900 MPa-10%) and TC18 (1330 MPa-1.7%). Incompatible plastic deformation behaviors of TC18 and TC4 enhance strain hardening effect, which is the main reason for the enhanced ductility of the composites. Refinement strengthening and heterostructure-deformation induced hardening are two key mechanisms to achieve the high strength. This study provides a new strategy to simultaneously enhance strength and ductility for Ti matrix composites.

High-temperature oxidation and wear properties of laser cladded Ti-Al-N composite coatings

Ti-Al-N composite coatings were in-situ synthesized on TC4 surfaces by laser cladding. The oxidation behaviors and wear properties of the as-obtained composite coatings and TC4 matrix were studied at various temperatures. The results showed the formation of a TiO2-dominated multilayer film on the composite coating surface at temperatures below 800 °C. The oxidation product of the coating contained a mixed oxide layer of TiO2 and Al2O3 at 900 and 1000 °C. The coatings exhibited good oxidation resistance at high temperatures. The thickening of the oxide film and distribution of the self-lubricating phase Ti2AlN in the coating decreased the friction coefficient to 0.2091. Also, the wear rate diminished to 0.025×10−4 mm3·N−1·m−1 at 800 °C, which is 1.43% that of the TC4 substrate. In the tested temperature range, the composite coatings showed mainly abrasive wear behavior, while an obvious lubrication effect was observed for oxide at high temperatures.

Microstructure and mechanical properties of in-situ TiC hybrid reinforced TC4 matrix composites by a new additive manufacturing method

As a new method to fabricate TiC-reinforced Ti matrix composites, pre-melted electron beam freeform fabrication was proposed based on in situ metallurgy using a graphite diversion nozzle. The feasibility of the method was investigated. Initially, the liquid TC4, an α+β Ti alloy, flowed into the graphite diversion nozzle, corresponding to the reaction between TC4 and graphite. Then, the fabrication of TiC occurred, achieving Ti matrix composites. The liquid TC4 was subsequently deposited on the TC4 substrate, indicating consolidated metallurgical bonding and the optimized hardness and abrasive resistance presented by the surface of the TC4 substrate. The deposited layer's microstructure and the TiC strengthening phase morphology in different areas were varied, considering the difference in the cooling rate and the flow mode. The distribution and morphology of the TiC strengthening phase in different regions were analyzed to reveal the underlying reasons for the property optimization of the TiC-TC4 deposited layer.

Simultaneous Improvement in Strength and Ductility of TC4 Matrix Composites Reinforced with Ti1400 Alloy and In Situ-Synthesized TiC

To overcome the tradeoff between strength and ductility of materials and obtain titanium matrix composites with excellent mechanical properties, in this study, the in situ-synthesized TiC particles and Ti-Al-V-Mo-Cr (Ti1400) alloy-reinforced Ti6Al4V (TC4) matrix composites ((Ti1400 + TiC)/TC4) were fabricated by low-energy ball milling and spark plasma sintering. The inhomogeneous distribution of TiC particles and Ti1400 alloy, as well as the compositional and structural transition zone, were characterized. The TiC/TC4 composite displayed a significantly higher yield strength and tensile strength compared to the TC4 alloy. However, the total elongation of the TiC/TC4 composite was only 57% of that in the TC4 alloy. In contrast, the (Ti1400 + TiC)/TC4 composites exhibited noticeably higher total elongation than the TiC/TC4 composite. Furthermore, the tensile strength of the composite increased with the increase in Ti1400 alloy content. The increase in strength can be attributed to solid solution strengthening and fine grain strengthening. The compositional and structural transition zone, formed by element diffusion, provided a better interface combination between the reinforcements and TC4 matrix. In the transition zone and Ti1400 region, a large number of α/β interfaces can effectively alleviate the stress concentration, and the increase in the β phase can bear more plastic deformation, which is conducive to improving the elongation of the composite. As a result, the (Ti1400 + TiC)/TC4 composites exhibited simultaneous improvements in strength and ductility.

Biomedical Mo particles reinforced titanium alloy fabricated by laser additive manufacturing

Modulus is an important factor in developing biomedical Ti-implants, and the high modulus of commercial TC4 alloy manufactured by laser powder bed fusion technology (LPBF) limits its applications in biomedical sector. This work proposed a low-cost and low-modulus 5 vol% Mo particles reinforced TC4 composites by LPBF with powder mixture. The results showed a phase transformation, which is the α′ phase to β phase via X-ray phase analysis due to the addition of Mo particles in the TC4 matrix, obtaining decreased modulus from 100±14 GPa to 64 ± 3 GPa and a significantly increased elongation from 14 ± 2% to 29 ± 1%. The fracture surface shows that the Mo particles’ plastic deformation can effectively improve the plasticity of Mo(p)/TC4 composites. This work may pave the way for developing low-modulus Ti-based composites for biomedical implants.

Effect of SiC content on microstructural evolution and tribology properties of laser-clad TiC-reinforced Ti-Al-Si composite coatings

This work prepared (Ti-Al-Si)-X (x = 1, 2, 3, 4) coatings on TC4 alloy matrix composites by laser cladding to improve their surface mechanical properties. Meanwhile, the effect of the content of SiC added to the Ti-Al-Si system on the properties and microstructures of the original coatings was explored. The results showed that the reinforced composite coatings contained matrix phases (TiAl, Ti3Al, TiAl3) and reinforcing phases (Ti5Si3 and TiC). As SiC content increased, the matrix phases formed in the coatings showed different results on the Ti-Al-Si ternary phase diagram due to the introduction of C, a stabilizer of ɑ-Ti alloy. Meanwhile, TEM results indicated the existence of Ti5Si3 phase and Ti3Al secondary phase in the Ti-Al-Si-3 layer. Compared with the TC4 matrix, the reinforced composite coatings had higher microhardness with average values of 780.9 HV0.3, 853.9 HV0.3, 985.0 HV0.3 and 943.5 HV0.3 for the four coatings, respectively. The wear resistance of the reinforced composite coatings increased first and then decreased with increasing SiC content, which was the result of the matrix phase transformation. The Ti-Al-Si-3 coating had the highest microhardness (1092HV0.3) and wear resistance (the friction coefficient, the wear scar width and wear weight loss were 0.37, ∼0.83 mm and 1.8 mg, respectively). The above analysis and results demonstrated that the Ti-Al-Si-3 layer had superior mechanical properties compared with those of other reinforced coatings.

Effect of Sintering Temperature on Room Temperature Microstructure of TiB Reinforced Titanium Matrix Composite

In this paper, the 3.5 vol.%TiB reinforced TC4 (Ti6Al4V) matrix composites were successfully fabricated using a mechanical ball milling and spark plasma sintering. The sintering temperature, sintering pressure and holding time were 700 °C~1100 °C, 40 MPa and 5 min, respectively. The 3.5 vol.% TiB/ TC4 matrix composites. The relative density of 3.5 vol.% TiB/TC4 composites increases with the increase of sintering temperature, and reaches saturation when the sintering temperature is 900 °C. The size of α-Lamellae increases from 1.47 μm to 2.44 μm with the increase of sintering temperature. The aspect ratio of TiB whiskers first increase and then decreases along with the solution time extending.

Comparison of the Laser-Repairing Features of TC4 Titanium Alloy with Different Repaired Layers

The laser repairing of TC4 holes was successfully performed with three and five layers under 2.5 mm and 1.0 mm diameters of laser spot, respectively. Experimental and numerical simulations were employed to clarify the influence of the repaired layers on microstructure, residual stress and strength. Optimized parameters were selected based on satisfactory formations. For the laser-repairing process with three layers, optimized parameters were selected as 1100 W laser power, 0.6 m/min scanning speed and 5 g/min powder feeding rate. For the laser-repairing process with five layers, optimized parameters were 800 W laser power, 0.9 m/min scanning speed and 3.5 g/min powder feeding rate. Numerical simulation showed that higher residual stress and larger repairing deformation would be produced when five repairing layers were adopted due to a more severe thermal accumulation effect. The microstructure from the TC4 matrix to the repaired area was orderly lamellar α phase + intercrystalline β phase-basketweave structure-martensite structure-widmannstatten structure. Tensile test results showed that higher tensile strength (910.5 MPa) would be obtained when three repaired layers were adopted.

Microstructure and properties of TiCx/TC4 composites with a quasi-network structure prepared by the decomposition of the Ti2AlC precursor

In the present study, a novel titanium matrix composite with a quasi-network structure was successfully fabricated via the hot-press sintering of the TC4 powder and Ti2AlC precursor at 1200 °C and 25 MPa. To explore the effect of the Ti2AlC content on the microstructure and properties of the prepared composites, 1–8 vol% Ti2AlC was selected as the representative samples. Microstructural analysis showed that the initial Ti2AlC was transformed into TiCx, and Al atoms diffused into the TC4 matrix to form a Ti(Al) solid solution. The α→β transformation temperature of Ti decreased based on thermal analysis. After increasing the amount of Ti2AlC, the α phase gradually shifted to equiaxed grains, and the grain size decreased, while the α/β ratio changed. When the content of Ti2AlC was 3 vol%, the composite’s strength significantly improved, with smaller ductility loss and a tensile yield strength of 939 MPa, tensile ultimate strength of 1007 MPa, compressive yield strength of 1292 MPa, and compressive ultimate strength of 2041 MPa. This strength improvement was attributed to fine-grain strengthening, solid-solution strengthening and second-phase strengthening. Moreover, theoretical calculations indicated that the solid-solution strengthening dominated the improvement efficiency.