Reinforced Ti 6Al 4V Research Articles

Microstructural characterization and mechanical properties of (TiB + TiC) reinforced Ti–6Al–4V prepared by melt hydrogenation

TiB and TiC reinforced Ti–6Al–4V matrix composites were prepared by melt hydrogenation, in which the total fraction of the reinforcements was 5 vol % and the ratio of TiB to TiC was 1:1. The effects of melt hydrogenation on the solidification process, phase composition, and microstructure of the titanium matrix were studied. The morphology and distribution of the reinforcement without and with hydrogen were observed. Moreover, the nano-hardness of the composites was measured. The results show that the solidification process of the matrix can be changed by melt hydrogenation, which resulting the increase of β phase and refining of α lamellar in titanium alloy. Hydrogen increased the size of the reinforcements, which aggregated at the grain boundary of the primary β phase and formed a network structure. Hydrogen reduced the nano-hardness both of the titanium alloy and the reinforcements slightly. In summary, melt hydrogenation can maintain or slightly reduce the strength of the composites at room temperature and decrease the nano-hardness.

Effect of ball milling time on microstructure and mechanical properties of graphene nanoplates and TiBw reinforced Ti–6Al–4V alloy composites

Ti–6Al–4V (TC4) matrix composites with graphene nanoplatelets (GNPs) and TiB whiskers (TiBw) were synthesized by ball milling, Fast Hot-Press Sintering (FHPS), and hot rolling (HR) method. The microstructures of the ball-milled powders, the as-sintered and as-rolled composites were characterized by Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. It revealed that there was an optimal ball milling time existed for obtaining GNPs with uniform dispersion and an acceptable degree of defects. The Raman results indicated that the defects increased and the number of GNPs layers decreased with the increasing ball milling time. Tensile tests revealed that the ultimate tensile strength of the 8-h-ball-milling composites increased from 1098 MPa to 1182 MPa and the elongation only dropped slightly from 16.0% to 15.1% compared with that of TC4 alloy fabricated under the same procedure. The failure mechanism of composites was further discussed by analyzing the fracture surface morphologies. Overall, this study highlights the effect of ball milling time on the structure integrity and dispersion homogeneity of GNPs, which is crucial to make full use of the excellent properties of GNPs in TC4 matrix composites.

The Microstructural Properties and Tribological Performance of Al2O3 and TiN Nanoparticles Reinforced Ti–6Al–4V Composite Coating Deposited on AISI304 Steel by TIG Cladding

Abstract This investigation presents the tribological performance of (Al2O3 + TiN)/Ti6Al4V cladding deposited on AISI304 steel substrate by the tungsten inert gas (TIG) cladding approach. The microstructural characterization by SEM confirmed claddings with visually crack-free and sound metallurgical bonding at the clad layer—substrate interface. The energy dispersive spectroscopy (EDS) analysis revealed the presence of matrix and reinforcement phases as major elements with the clad layer and with considerably no oxidation during their deposition. The XRD spectra revealed that matrix and reinforcements are dominant phases in the clad layer. The formation of compounds reflected considerably a lower dilution of reinforcement phase with Ti6Al4V matrix during melting and deposition. Higher the microhardness of the (Al2O3 + TiN)/Ti6Al4V clad layer in the cladding zone compared with other clad layer compositions such as Ti6Al4V, Al2O3/Ti6Al4V, and TiN/Ti6Al4V, it is varied from 1130HV0.2 to 1222HV0.2, and the average microhardness is about 990.57HV0.2 which is 175% improvement compared with the substrate. The cladding with dual reinforcement composition has shown a superior wear resistance compared with all other clad layer composite compositions. The improvement in the wear resistance achieved with (Al2O3 + TiN)/Ti6Al4V composite clad layer deposition at 2.5 m/s, 3.5 m/s, and 4.5 m/s sliding velocities is 56.60%, 63.26%, and 68.53%, respectively, compared with the substrate. The wear morphology of the composite claddings is relatively smoother and the wear furrows are shallower compared with the substrate, especially for the composite clad layer with (Al2O3 + TiN) reinforcement phase.

Direct energy deposition of SiC reinforced Ti–6Al–4V metal matrix composites: Structure and mechanical properties

The creation of metal matrix composites (MMCs) is an important strategy for obtaining heat-resistant products. Metal matrix composites provide superior characteristics of improved mechanical, high-temperature and tribological properties. Manufacturing of MMCs by the methods of additive technologies contributes to the development of technical industries. In this paper, the formation of the structure, phase composition and mechanical properties of Ti–6Al–4V/SiC MMCs got by direct energy deposition were investigated. The compositions with 1 vol%, 3 vol%, 5 vol%, 7 vol% SiC are considered. The structure consists of SiC particles surrounded by a matrix of titanium martensite. However, during deposition, the matrix interacts with SiC particles to form TiC and Ti5Si3. Increasing the amount of ceramic content leads to a reduction of grains, which is associated with the formation of TiC at the grain boundaries. As the SiC content increases, the hardness increases because of an increase in the solid phases TiC and Ti5Si3, but these phases weaken the DED samples. The addition of 1 vol% SiC significantly increases the strength of the titanium alloy up to 1300 MPa with a relative elongation of 2.1%.

Microstructure and mechanical properties of GNPs and in-situ TiB hybrid reinforced Ti–6Al–4V matrix composites with 3D network architecture

Graphene nanoplatelets (GNPs) and TiB whiskers (TiBw) hybrid reinforced Ti–6Al–4V (TC4) matrix composites ((GNPs + TiBw)/TC4) were fabricated by Fast Hot-Press Sintering (FHPS) and hot rolling (HR) method. The microstructure, mechanical properties and strengthening mechanisms were systematically studied with various TiBw contents. Microstructure observation results indicate that GNPs can be mostly preserved and TiBw are rarely obtained during the sintering process. HR process was applied to further densify the composites and obtain the in-situ TiBw. The high ductility of composites was achieved via designing network structure with reinforcements of GNPs and in-situ TiBw, which reduce the interface reaction of the GNPs/Ti and improved the interface bonding. The tensile ductility of the GNPs/TC4 composites were improved with the addition of TiB2 powders. As a result, 0.1 wt% GNPs/TC4 composites with the addition of 0.05 wt% TiB2 powders showed the best combination of ultimate tensile strength of 1158 MPa and a fracture elongation of 15.8%. Compared to the fracture elongation of pure TC4 alloy (15.2%), there was no sacrifice of ductility.

Spark Plasma Forging and Network Size Effect on Strength-Ductility Trade-Off in Graphene Reinforced Ti6al4v Matrix Nanocomposites

Spark Plasma Forging and Network Size Effect on Strength-Ductility Trade-Off in Graphene Reinforced Ti6al4v Matrix Nanocomposites

Utilizing Additive Friction Stir Processing to Fabricate B4C Reinforced Ti–6Al–4V Matrix Surface Composite: Microstructure Refinement and Enhancement in Mechanical Properties

Utilizing Additive Friction Stir Processing to Fabricate B4C Reinforced Ti–6Al–4V Matrix Surface Composite: Microstructure Refinement and Enhancement in Mechanical Properties

Super-high-strength graphene/titanium composites fabricated by selective laser melting

Poor chemical stability of graphene in titanium (Ti) is one critical problem to make use of the extraordinary properties of graphene for obtaining high-performance graphene/Ti composites. To overcome this problem, the selective laser melting (SLM) process with rapid heating and cooling characteristics was exploited to fabricate graphene nanosheet (GNS)-reinforced Ti–6Al–4V matrix composite in this study. Results showed that the SLMed composite registered super-high tensile strength (1526 MPa) and high Young’s modulus (145 GPa), which were 73% and 26% lager than those of spark plasma sintered composites fabricated from the same powder mixture, respectively. It was found that the locally reacted GNSs and in-situ formed ultrafine TiC particles mainly contributed to the outstanding mechanical properties of SLMed GNSs/Ti composites. The underlying mechanism was thoroughly discussed based on microstructures and strengthening models. The results pave up the way towards the fabrication of super-strong Ti matrix composites.

Diffusion bonding of TiC or TiB reinforced Ti–6Al–4V matrix composites to conventional Ti–6Al–4V alloy

ABSTRACT The diffusion bonding of conventional alloy Ti–6Al–4V (Ti-64) and composites of this alloy with 10% of TiC or TiB fabricated using blended elemental powder metallurgy was successfully carried out at 850–1000°C, with a holding time of 60 min under 0.7–1.5 MPa pressure. The metallographic and electron backscattered diffraction studies as well as the bending and microhardness tests across the bonds are presented as the evidence of joint integrity. The selected experimental parameters do not cause undesirable structural changes (degradation) in the base metals adjacent to the bond interface. Particle reinforcement at ∼10% did not appear to modify bonding parameters when compared to the unreinforced Ti-64 alloy.

Oxidation behavior of in situ synthesized (TiB + TiC)/Ti–6Al–4V composites from Ti–B4C–C and Ti–TiB2–TiC systems

Abstract

Production and mechanical properties of nano SiC particle reinforced Ti–6Al–4V matrix composite

Different mass fractions (0, 5%, 10%, and 15%) of the synthesized nano SiC particles reinforced Ti–6Al–4V (Ti64) alloy metal matrix composites (MMCs) were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density (93.33%) was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic (SEM) observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.

Microstructural aspects of in-situ TiB reinforced Ti–6Al–4V composite processed by spark plasma sintering

Titanium-matrix composites have important and wide applications in the transport and aerospace industries. The current research was focused on powder metallurgy processing of in-situ reinforced titanium-matrix composite with TiB whiskers. The Ti–6Al–4V alloy and B4C additive powders were used as raw materials. Two different consolidation techniques, namely press-and-sintering and spark plasma sintering, were selected. It was observed that in-situ TiB whiskers were formed during sintering in both methods. The changes in size, aspect ratio and distribution of in-situ whiskers in different composite samples were monitored. The effect of spark plasma sintering temperature on the synthesis of in-situ whiskers was also investigated. Based on the microstructural observations (optical microscopy and scanning electron microscopy) and the energy dispersive spectroscopy analysis, it was concluded that increasing the spark plasma sintering temperature from 900 to 1100 °C would lead to the complete formation of in-situ TiB whiskers and reduced porosity content.

Fatigue properties and fracture analysis of a SiC fiber-reinforced titanium matrix composite

Tension–tension fatigue properties of SiC fiber reinforced Ti–6Al–4V matrix composite (SiCf/Ti–6Al–4V) at room temperature were investigated. Fatigue tests were conducted under a load-controlled mode with a stress ratio 0.1 and a frequency 10Hz under a maximum applied stress ranging from 600 to 1200MPa. The relationship between the applied stress and fatigue life was determined and fracture surfaces were examined to study the fatigue damage and fracture failure mechanisms using SEM. The results show that, the fatigue life of the SiCf/Ti–6Al–4V composite decreases substantially in proportion to the increase in maximum applied stress. Moreover, in the medium and high life range, the relationship between the maximum applied stress and cycles to failure in the semi-logarithmic system could be fitted as a linear equation: Smax/μ=1.381−0.152×lgNf. Fractographic analysis revealed that fatigue fracture surfaces consist of a fatigued region and a fast fracture region. The fraction of the fatigued region with respect to the total fracture surface decreases with the increase of the applied maximum stresses.

Effect of in situ synthesized TiB whisker on microstructure and mechanical properties of carbon–carbon composite and TiB w/Ti–6Al–4V composite joint

Carbon–carbon composite (C–C composite) and TiB whiskers reinforced Ti–6Al–4V composite (TiB w /Ti–6Al–4V composite) were brazed by Cu–Ni + TiB 2 composite filler. TiB 2 powders have reacted with Ti which diffused from TiB w /Ti–6Al–4V composite, leading to formation of TiB whiskers in the brazing layer. The effects of TiB 2 addition, brazing temperature, and holding time on microstructure and shear strength of the brazed joints were investigated. The results indicate that in situ synthesized TiB whiskers uniformly distributed in the joints, which not only provided reinforcing effects, but also lowered residual thermal stress of the joints. As for each brazing temperature or holding time, the joint shear strength brazed with Cu–Ni alloy was lower than that of the joints brazed with Cu–Ni + TiB 2 alloy powder. The maximum shear strengths of the joints brazed with Cu–Ni + TiB 2 alloy powder was 18.5 MPa with the brazing temperature of 1223 K for 10 min, which was 56% higher than that of the joints brazed with Cu–Ni alloy powder.

Microstructure evolution of single crystal WC p reinforced Ti–6Al–4V metal matrix composites produced at different cooling rates

Laser melt injection (LMI) and vacuum arc melting (VAM) were explored to prepare single crystal WC particles (WC p) reinforced Ti–6Al–4V metal matrix composites (MMCs). The microstructure evolution of the produced WC p/Ti–6Al–4V MMCs and the interfacial reaction between WC p and liquid Ti at different cooling conditions were investigated. The interfacial reaction of WC p with Ti was sensitive to the cooling rate of the melt pool. The formation of the compact TiC layer during the rapid cooling rate in LMI intercepted the dissolution of WC p and inhibited the interfacial reaction and consequently resulted in the formation of thin reaction layers around WC p. Under the condition of slow cooling rate in VAM, the reaction between WC p and Ti melt was rather intensive and thick reaction layers consisting of W 2C and TiC were formed.

Three-dimensional microstructural characterization of discontinuously reinforced Ti64–TiB composites produced via blended elemental powder metallurgy

Three-dimensional (3D) microstructures of TiB reinforcement in two discontinuously reinforced Ti–6Al–4V (Ti64) alloy composites produced via blended elemental (BE) powder metallurgy are reconstructed from large-area high-resolution optical montage serial sections. The TiB phase in both composites shows whisker morphology with roughly hexagonal cross-sections, a unimodal size distribution, and uniform random morphological orientations. The TiB whiskers in these composites are significantly coarser compared to similar materials produced via pre-alloyed powder metallurgy but did not contain coarse primary TiB particles.

Effects of the coating system and interfacial region thickness on the thermal residual stresses in SiC f/Ti–6Al–4V composites

A three-dimensional finite element model was developed to study effects of the coating system and interfacial region thickness on the distributions of the thermal residual stresses in continuous SiC fiber reinforced Ti–6Al–4V composite. Three coating systems were applied in this study, that is, C coating, C/TiB 2 coating and without coating. The influence of the interfacial region thickness on the thermal residual stresses in the composite was analyzed with concerning the simple case of without coating. Some proposal was given for the interface structure design of the composites. With regard to the thermal residual stresses, the C coating is an advisable choice for the interface structure design of the continuous SiC fiber reinforced Ti–6Al–4V composites. And for the region of the interfacial region thickness from 1 μm to 3 μm, the thicker interfacial region can reduce most of the thermal residual stresses in composites and improve the axial tensile strength of the composite.

WC p/Ti–6Al–4V graded metal matrix composites layer produced by laser melt injection

The laser melt injection (LMI) process was explored to produce WC particles (WC p) reinforced Ti–6Al–4V metal matrix composites (MMC). In particular monocrystalline WC powder was used as injection particles to avoid the intercrystalline cracking often observed in granular or cast WC p reinforced MMC. WC p were injected into the extended part of the melt pool just behind the laser beam. The process allowed for the minimization of the WC p dissolution caused by the direct irradiation of the laser beam, and the decomposition reaction between WC p and Ti melt. Different parameters were applied, and a processing window of LMI was obtained. WC p exhibit a graded distribution along the depth direction of the MMC layer. New phases such as TiC and W 2C are observed in the MMC layer, in which TiC is the predominant phase. TiC grains present a continuous decrease in both amount and size with the distance from the surface to the bottom of the MMC layer. Two types of reaction layers around WC p can be distinguished, namely an irregular reaction layer and a cellular reaction layer. The growth and final morphology of reaction layers are most likely being dominated by the composition of the neighbouring melt pool. A gradual hardness distribution in the depth direction of the composites layer is observed. Moreover, the transition from the MMC layer to the substrate also exhibits a gradual change in the hardness.

Effect of the interfacial reaction layer thickness on the thermal residual stresses in SiCf/Ti–6Al–4V composites

A three-dimensional finite element model was developed to study the effects of the interfacial reaction layer thickness on the distribution of the thermal residual stresses near the interfacial reaction layer in continuous SiC fiber reinforced Ti–6Al–4V composite. The interfacial reaction layer thicknesses in real composites were adopted in the present analysis. The hoop, radial and axial stresses at the fiber and interfacial reaction layer (f/i interface), middle of the interfacial reaction layer and interfacial reaction layer and matrix (i/m interface) were studied for each thickness. The results show the interfacial reaction layer thickness has a significant influence on the distribution of the thermal residual stresses near the interfacial reaction layer. X-ray stress measurements indicate that the prediction data have a good agreement with the experimental results. The interfacial radial cracks appear not only in the as-processed sample but also in the heat-treated samples. Experimental observations suggest that the f/i interfacial debonding is not significant during the transverse tensile loading.

Surface nanodeformation of discontinuously reinforced Ti composite by in situ atomic force microscope observation

The surface nanodeformation of a discontinuously reinforced Ti–6Al–4V composite during tensile loading was investigated by in situ atomic force microscope (AFM) observation. The material used was a TiB whisker and TiC particle reinforced Ti–6Al–4V composite. The evolution of surface roughness and slip band spacing was quantified as a function of applied strain. The microstructural damage during tensile loading was also studied. The formation of slip bands within a grain of the Ti–6Al–4V matrix was clearly observed when the applied strain above was 1.3%. The amount of slip bands and surface roughness increase with increasing applied strain. The rupture of TiC particle and multiple cracking of TiB whiskers were also observed at the applied strain above 1.3%. The interaction of slip bands with the reinforcements and mechanisms of deformation and fracture of the composite were elucidated.