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Despite the fact that the additive manufacturing (AM) technique has been established for almost two decades, its optimisation is still performed by trial and error experimentation. In the present work, a finite element modelling approach was used to study both the temperature distribution and heat flux vector characteristics during multi-layer deposition of a Ti–6Al–4V alloy that take place in the AM process. The results revealed the difference between different powder deposition time intervals on thermal cycles, heat flux vectors and the resulting microstructures. Good agreement between the numerical and experimental results was found. The results obtained can be used for process optimisation. [ABSTRACT FROM AUTHOR]

Abstract Laser direct melting deposited (LDMD) Ti-6Al-4V alloys are mainly used in aerospace fields. It is very important to study their deformation behavior as a function of the application conditions (i.e. temperature and stress). This work compared the dynamic microstructure evolution and mechanical properties of LDMD Ti-6Al-4V alloys at 23 ℃ and 650 ℃. A method based on in-situ scanning electron microscopy (SEM) tensile testing was used to identify the initiation of cracks and propagation mode of slip bands. The deformation mechanisms at low and elevated temperatures were discussed. The results showed that the strength decreased and the elongation increased with increasing temperature. These results were verified by the propagation modes of slip bands and opening of the active deformation systems. [ABSTRACT FROM AUTHOR]

Abstract Laser cladding of Ti-6Al-4V powder on a substrate with the same chemical composition was performed at different laser powers. The effect of laser power on the microstructure and corrosion behavior was then investigated. Electrochemical studies were performed by potentiodynamic polarization tests in different corrosive environments (3.5% NaCl, 2% H 2 SO 4 and 5% HCl solutions). Microstructural investigation together with phase characterization revealed that laser cladded Ti-6Al-4V coatings were composed of needle-like martensite (ɑ/) and coaxial hexagonal compact (ɑ) phases. The coatings were crack-free; however, some cavities were observed in the coatings produced at high laser powers. In all three corrosive environments, the coatings showed a more noble corrosion behavior compared to the untreated substrate. The results showed that corrosion potential increases from −410 (mV) to −130 (mV) in NaCl and from −50 (mV) to −20 (mV) in H 2 SO 4 enviroments but decreases from −60 (mV) to −270 (mV) in HCl solution. Increasing laser power had a positive effect on the corrosion behavior in NaCl and H 2 SO 4 solutions; however, it had a negative effect on the corrosion behavior in HCl solution. Highlights • Laser cladded Ti-6Al-4V powder on Ti-6Al-4V substrate using a Nd:YAG laser. • The effect of the laser cladding process on microstructure was investigated. • The corrosion behavior in different solution after laser cladding on Ti-6Al-4V alloy was evaluated. [ABSTRACT FROM AUTHOR]

Abstract The bead geometry of autogenous bead-on-plate tungsten inert gas (TIG) welding performed on Ti-6Al-4 V alloy inside an argon inert box chamber was measured for different processing conditions. The microstructural evolution of the weldment was evaluated through optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) technique. The development of residual stress and the texture in the weldment were assessed through the XRD techniques. The full penetration melting for bead-on-plate welding was obtained for high current and low scan speed combination that induces maximum heat input within the experimental domain. Owing to intense heat of the TIG arc, a complex microstructural evolution occurred in the Ti-6Al-4 V alloy, which causes transformation of initial β phase to martensitic α' phases. The transformation of initial α + β phase to martensitic α' phase enhances the hardness value of the melt pool upto 365 HV 0.2 , and further at heat affected zone (upto 385 HV 0.2) owing to grain refinement. The residual stress developed in the weld melt pool was recorded tensile type, and for increasing the welding current, due to the enhancement of induced heat, the residual stress increased from 140 to 200 MPa (for 80 A) to 240–270 MPa (for 100 A). [ABSTRACT FROM AUTHOR]

Abstract In general, mechanical properties of most materials under dynamic loading are completely different from those under static/quasi-static loading. In this paper, a comparative study between the selective laser melted Ti-6Al-4V alloy and its heat-treated counterpart was carried out. After heat treatment, the microstructure transformed from full fine acicular α' into basket-weave morphology with coarsened α + β lamella, grain boundaries α tended to globularization, and the volume fractions of β phase and LAGBs increased due to the α′→α + β transformation and increasing of dislocation density respectively. During high strain rate tension, strain was dispersive in the elastic deformation region, then it began to concentrate at the centre of samples and increased until fractured as loading time increased. As expected, evident reduction in the UTS and σ y and increase in the ε were caused by heat treatment, however both of them increased as the strain rate increased due to the twinning deformation occurred in the α/β interface phase, thus contributed to improving the strength and plasticity of SLMed TC4 alloy under high strain rate loading simultaneously. This work provided a relationship between microstructure and dynamic responses of SLMed TC4 alloy, which contributes to exploiting the performance potential of SLMed alloy. [ABSTRACT FROM AUTHOR]

Abstract In the present work, the characteristics of α texture transformed from the strong <100> β fiber texture and their effect on the tensile deformation behavior of Ti–6Al–4V alloy fabricated using electron beam rapid manufacturing (EBRM) have been investigated. The results show a concentrated distribution of transformed α texture along the transverse direction (TD) while a relatively random distribution along the longitudinal direction (LD). This different orientation distribution of α phase leads to anisotropy in tensile strength. Moreover, inhomogeneous deformation is found in the longitudinal sample, which is not observed in the transverse sample. This can also be attributed to the relatively discrete α orientation distribution in the LD. The relationship between the deformation ability of each columnar prior β grain and its corresponding crystallographic orientation was investigated. Both the calculated and experimental results indicate that a relatively low deformation resistance is found when the angle of the [001] β direction of a columnar grain to the LD is relatively small and a higher deformation resistance is found when the angle is about 45°. During the loading process in the LD, deformation may concentrate in some "weak" columnar grains with relatively low deformation resistance, resulting in decreased integral ductility compared to the transverse sample. [ABSTRACT FROM AUTHOR]

Abstract The gradient nanostructure evolution and the mechanism governing this evolution of α phase in Ti-6Al-4V alloy induced by ultrasonic surface rolling process were investigated. A gradient nanostructure consisting of a roughly equiaxed nanograin layer, an elongated nano-lamellar layer, an elongated ultrafine lamellar layer, a refined grain layer, and a low-strain coarse-grained layer was formed with a thickness of more than 400 µm. The formation of gradient nanostructure of α phase was dominated by complex dislocation activities in hcp grains without twins occurring, supplemented by hexagonal close-packed (hcp) titanium (Ti) to face-centered cubic (fcc) Ti phase transformation. During the microstructural evolution, the coarse hcp-Ti grains were first elongated into lamellae. Then, these sub-micron lamellae were gradually transformed into roughly equiaxed nanograins via two deformation modes of longitudinal splitting and transverse breakdown, accompanied by dynamic recovery. The fcc-Ti grains were deformed mainly via twin-twin intersections and twin-dislocation interactions, accompanied by longitudinal splitting and transverse breakdown, resulted in refinement of the micron-scale fcc-Ti grains to roughly equiaxed nanograins. The interaction of hcp and fcc phases influenced and synergistically promoted the microstructural evolution process. In addition, the microhardness improvement in the surface layer of Ti-6Al-4V alloy was attributed to the increase of dislocation density, grain refinement and the occurrence of deformation twinning in fcc-Ti grains. [ABSTRACT FROM AUTHOR]

Abstract Hot deformation behavior of the Ti-6Al-4V alloy is studied through hot torsion tests. Cylindrical samples are twisted at different strain rates and temperatures in the β phase domain. The recorded torque vs twisting angle data are converted to strain vs stress data using the appropriate methods. All the flow curves obtained are characteristic of continuous dynamic recrystallization. The flow stresses exhibit rapid growth to reach a single maximum followed by a decrease and a steady-state regime. The influence of strain rate and temperature is taken into account. An analytical model is proposed, which gives accurate flow curves for the Ti-6Al-4V alloy for processing temperatures between 1000 °C and 1100 °C and strain rates between 0.01/s and 1/s. The model is validated by further experimental tests. Graphical abstract Unlabelled Image Highlights • Hot deformation behavior of the Ti-6Al-4V alloy is studied through hot torsion tests. • Analytical modeling of hot behavior of Ti-6Al-4V alloy at large strain is proposed. • The model gives flow curves for processing temperatures between 1000°C and 1100°C and strain rates between 0.01/s and 1/s. • The model is validated by further experimental tests. • The model takes into account the continuous dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Titanium alloy (Ti-6Al-4V) has been mostly used for medical implants due to its good chemical and mechanical properties. However, this alloy has tendency to emanate toxic V and Al due to its low corrosion resistance in body conditions. In this work, an experimental study of laser cladding Ti-Al2O3 coatings with different Al2O3 fractions (5 wt.% Al2O3, 8 wt.% Al2O3, and 10 wt.% Al2O3) was carried out to establish a coating which could improve the hardness and corrosion resistance of Ti-6Al-4V alloy. Laser parameters of 900 W power, 0.6 m/min laser scan speed, and 2 l/min powder feed were used in this research. The microstructure, phase constituents, microhardness, and corrosion of the resultant coatings were characterized by scanning electron microscope (SEM), optical microscope (OPM), X-Ray Diffractometer (XRD), Vicker hardness tester, and potentiostat respectively. Results showed that a defect free coating was achieved at a coating with less Al2O3 content. Increase in Al2O3 addition resulted in increment of hardness with Ti-10 wt.% Al2O3 coating achieving an optimum hardness of about 2.2 times greater than that of the substrate. Moreover, considerable increment in corrosion resistance of Ti-6Al-4V alloy was achieved after laser deposition of various Ti-Al2O3 admixed coatings. An optimal corrosion rate reduction of about 81% and polarization resistance increment of 709% over the substrate were achieved at Ti-5 wt.% Al2O3 due to low porosity within the coating layer. It has been established that fabricating Ti-Al2O3 on Ti6Al4V through laser could be used in improving the surface hardness values and corrosion resistance. [ABSTRACT FROM AUTHOR]

Abstract In this study, four straight walls of Ti-6Al-4V titanium alloy were fabricated by wire and arc additive manufacturing (WAAM) to investigate the effect of deposition parameters on grain morphology evolution and texture characterization in the building direction. A certain volume fraction of equiaxed β grain appeared at the bottom of the wall and can be controlled by deposition parameters, while the columnar β grain zone was on the equiaxed β grain zone. It is indicated that the formation of equiaxed β grains at the bottom of the wall initiated from the recrystallization. There were the large residual stress, strain, and high heating rate when depositing the first several layers near the substrate, which can induce the recrystallization of the already-deposited layers. However, the preferred crystallographic orientations along the building direction formed gradually during the deposition process, then the β grains began to grow epitaxially from the already-deposited layers, and changed to columnar β grains, which lead to a strong 〈001〉 fiber texture in the building direction. In addition, there are also some equiaxed β grains at the top surface of the wall due to the occurrence of the columnar to equiaxed grain transition (CET) in the molten pool. Graphical abstract Image 1 Highlights • A large volume fraction of equiaxed β grains can be obtained in WAAMed Ti-6Al-4V. • Alternative growth between equiaxed and columnar grains can be obtained. • Recrystallization is observed during the WAAMed Ti-6Al-4V process. • The formation of equiaxed β grains is due to various factors. • The texture of equiaxed β grains is much weaker than that of columnar β grains. [ABSTRACT FROM AUTHOR]

Abstract Ti-6Al-4V alloy with local anisotropic characteristics is produced by electropulsing treatment (EPT) and used in ultraprecision rotary diamond cutting to explore the deformation mechanism of the alloy. Two different orientations of lamellar martensite α give rise to the local anisotropic behaviour. Critical resolved shear stress (CRSS) is introduced in this paper to investigate the slip modes of the hexagonal closest packing martensite. A geometrical and physical model is also proposed for calculation of resolved shear stresses on various slipping systems. The results show that glide occurs in some certain directions on the condition that resolved shear stress equals or exceeds the CRSS. The cutting force varies with martensitic orientations, which is supposedly due to the combined effects of lamellar α phase sizes and the coordination or competition of diverse slipping directions. Highlights • Anisotropic Ti-6Al-4V alloy is produced by electropulsing treatment. • Ultraprecision rotary diamond cutting is conducted on samples. • A model is proposed for calculation of resolved shear stresses. • Cutting force varies with martensitic orientations. • Different slip systems could be activated with the forward of diamond tools. [ABSTRACT FROM AUTHOR]

A cold-rolled Ti-6Al-4V alloy was subjected to consecutive heat treatments at 1283 K for 1 h and at 823 K for 3 h in order to produce a fully lamellar microstructure. Thereafter, the material was processed by high-pressure torsion (HPT) through various numbers of turns up to a maximum of 30. It is shown that the HPT processing leads to exceptional grain refinement with average grain sizes of ~ 70 and ~ 50 nm after 20 and 30 turns, respectively. Tensile testing was conducted at 873 and 923 K with different initial strain rates using the material processed through 20 turns of HPT and this gave a maximum superplastic elongation of 820% at the relatively low temperature of 923 K when testing with an initial strain rate of 5.0 × 10 −4 s −1 . The associated strain rate sensitivity for this low temperature superplasticity was estimated as m  ≈ 0.5 which is consistent with flow by grain boundary sliding. [ABSTRACT FROM AUTHOR]

The marine, aerospace, and power machinery industries show progression in the application of titanium alloy components due to their good properties. However, the alloy exhibits poor thermal stability, low hardness, and poor tribological properties; as a result, the use of Ti6Al4V in various industries is restricted. Consequently, a search for surface improvement of Ti6Al4V alloy arose with the intention of enhancing its endurance. The use of laser metal deposition method by integrating chemical barrier coatings is considered as advantageous; therefore, an investigation aimed at surface improvement of Ti6Al4V by incorporation of Ti-Co coatings developed. To fabricate the coatings, a 3-kW continuous wave ytterbium laser system (YLS) was used, and to control the movement of the cladding process, a KUKA robot was attached to the system. The microstructure, corrosion, and mechanical properties of the titanium alloy-cladded surfaces were studied at different laser process parameters. To analyze the microstructure of the cross section, optical and scanning electron microscopy were employed. A laser power of 750 W and scanning rate of 1.2 m/min were found to be the optimum process conditions for a 60Ti-40Co alloy. When comparing the mechanical properties of the alloy and bare substrate, the alloy exhibited a significant increase in terms of the hardness. It was found to have 719 HV as compared to 301 HV which is that of the substrate, this indicates to an increase of 58.14% in the hardness. Lower laser scanning rates result in a larger fraction of hard-intermetallic phases which in turn lead to coatings with enhanced hardness levels. Furthermore, the yield strength and tensile strength of the coatings increased to maxima of 2.30 and1.66 GPa, respectively in comparison to the substrate, due to the addition of Co. Additionally, the corrosion rates of all the coated specimens were reduced as a result of the oxide films formed on the laser-coated Ti6Al4V alloy samples. [ABSTRACT FROM AUTHOR]

Titanium alloys are the primary candidates in several applications due to its promising characteristics, such as high strength to weight ratio, high yield strength, and high wear resistance. Despite its superior performance, some inherent properties, such as low thermal conductivity and high chemical reactivity lead to poor machinability and result in premature tool failure. In order to overcome the heat dissipation challenge during machining of titanium alloys, nano-cutting fluids are utilized as they offer higher observed thermal conductivity values compared to the base oil. The objective of this work is to investigate the effects of multi-walled-carbon nanotubes (MWCNTs) cutting fluid during cutting of Ti-6Al-4V. The investigations are carried out to study the induced surface quality under different cutting design variables including cutting speed, feed rate, and added nano-additive percentage (wt%). The novelty here lies on enhancing the MQL heat capacity using nanotubes-based fluid in order to improve Ti-6Al-4V machinability. Analysis of variance (ANOVA) has been implemented to study the effects of the studied design variables on the machining performance. It was found that 4 wt% MWCNTs nano-fluid decreases the surface roughness by 38% compared to the tests performed without nano-additives, while 2 wt% MWCNTs nano-fluids improve the surface quality by 50%. [ABSTRACT FROM AUTHOR]

Simulated multipass deformation experiments were carried out via torsion testing on a Ti-6Al-4V alloy in the two-phase region under both isothermal and continuous cooling conditions. Flow softening was observed during the isothermal multipass deformation tests as indicated by the evolution of the mean flow stress (MFS). The MFS values increased with interpass time from 2 s to 32 s. Using BSE-SEM characterization techniques, dynamic phase transformation (alpha to beta) and coarsening of the alpha phase took place. The quantitative results indicate that the alpha phase transforms into beta during straining, but it retransforms statically into alpha by amounts that increase with interpass time. The flow softening observed is the net result of softening by dynamic transformation and hardening by reverse transformation. [ABSTRACT FROM AUTHOR]

An ultrafine microstructure consisting of α grains (~ 0.51 µm) and a small amount of β phase was successfully achieved in a friction stir-processed (FSPed) Ti-6Al-4V alloy. The fraction of high angle grain boundaries (HAGBs) with random crystallographic orientations reached 89.3% revealed that dynamic recrystallization was responsible for the ultra-grain refinement mechanism during friction stir processing (FSP). Low-temperature superplasticity (LTSP) of such an ultrafine microstructure was demonstrated in the temperature range of 550–650 °C and strain rates of 1 × 10 −4 –3 × 10 −3 s −1 . Specifically, an extremely superior LTSP of 1130% was achieved at 600 °C and 3 × 10 −4 s −1 , which was explained by means of the ultrafine equiaxed grains, a large proportion of HAGBs with random orientations as well as the presence of β phase. The predominant superplastic deformation mechanism was considered as grain boundary sliding associated with grain boundary diffusion. [ABSTRACT FROM AUTHOR]

This study investigates the relationships between corrosion resistances, microstructure and phase composition of Ti-6Al-4V components that have been fabricated with the gas tungsten wire arc additive manufacturing (GT-WAAM) process, through the use of electrochemical corrosion testing, optical microscopy, X-ray diffraction and hardness testing. The corrosion behaviour is anisotropic due to corresponding anisotropy in microstructure, phase structure, grain size and orientation within the WAAM-processed Ti-6Al-4V alloy. Compared to ASTM standard wrought Ti-6Al-4V, the WAAM-processed alloy has a slightly inferior corrosion resistance owing to the formation of asymmetrical structures with lamellar α and acicular α’ phases, that display preferred orientation. [ABSTRACT FROM AUTHOR]

The effect of electropulsing-assisted ultrasonic nanocrystalline surface modification (EP-UNSM) on surface mechanical properties and microstructure of Ti-6Al-4V alloy is investigated. Compared to conventional ultrasonic nanocrystalline surface modification (UNSM), EP-UNSM can effectively facilitate surface roughness and morphology, leading to excellent surface roughness (reduced from Ra 0.918 to Ra 0.028 μm by UNSM and Ra 0.019 μm by EP-UNSM) and smoother morphology with less cracks and defects. Surface friction coefficients are enhanced, resulting in lower and smoother friction coefficients. In addition, the surface-strengthened layer and ultra-refined grains are significantly enhanced with more severe plastic deformation and a greater surface hardness (a maximum hardness value of 407 HV and an effective depth of 550 μm, in comparison with the maximum hardness value of 364 HV and effective depth of 300 μm obtained by conventional UNSM). Remarkable enhancement of surface mechanical properties can be attributed to the refined gradient microstructure and the enhanced severe plastic deformation layer induced by coupling the effects of UNSM and electropulsing. The accelerated dislocation mobility and atom diffusion caused by the thermal and athermal effects of electropulsing treatment may be the primary intrinsic reasons for these improvements. [ABSTRACT FROM AUTHOR]

The plasma immersion ion implantation treatment (PIII) acts to increase mechanical resistance with solid solution formation, new phases and defects inclusion, besides chemical and residual stress profile modification. Ti-6Al-4V alloy presents poor tribological properties and high affinity with interstitial elements, such as nitrogen and oxygen, this makes it more reactive at high temperatures. This paper aims to study Ti-6Al-4V alloy fatigue behavior subjected to nitrogen addition by plasma immersion ion implantation. It was investigated the frequency parameter influence on fatigue resistance. Ti-6Al-4V alloy was PIII treated with voltage equal to 9.5 kV, frequencies varying between 1000 and 1500 Hz and submitted to axial fatigue tests. Axial fatigue tests were performed, at room temperature and R = 0.1. Ti-6Al-4V alloy fatigue results were supported by Weibull statistics analysis. Ti-6Al-4V alloy microstructural analysis showed equiaxed α + β grains. Weibull analysis at untreated condition presented m values greater than 1, indicating reliability and uniformity. For a lifetime of 10 7 cycles, fatigue resistance was equal to 829 MPa for untreated condition, 644, 767 and 417 MPa, for f  = 1000, 1200 and 1500 Hz, respectively. The nitrogen-based compounds were detected only at the condition where f  = 1200 Hz. Thus, the combination of PIII treatment parameters, when f  = 1200 Hz, hindered crack nucleation and increasing fatigue resistance of treated Ti-6Al-4V alloy when compared with the other two treatment conditions. [ABSTRACT FROM AUTHOR]

The tribocorrosion behavior of Ti-6Al-4V alloy as produced using different manufacturing/processing methods is experimentally investigated. Various Ti-6Al-4V specimens sourced from either casting, hot pressing (HP) or Laser Engineered Net Shaping (LENS) processes were analyzed via reciprocating sliding alumina contact tests under open circuit potential (OCP). Results indicate that the tribocorrosion behavior of Ti-6Al-4V parts depends on its manufacturing method. The additive manufactured, LENS Ti-6Al-4V samples showed better wear and corrosion resistance as compared to the Ti-6Al-4V samples produced by either casting or HP. This unique characteristic is attributed to the very high, localized cooling rates experienced during LENS resulting in the Ti-6Al-4V material having higher hardness and slight chemistry variation. [ABSTRACT FROM AUTHOR]

The mechanical properties of the Ti-6Al-4V alloy are significantly determined by the process used for manufacture. In this study, the mechanical properties of the Ti-6Al-4V alloy manufactured using cold rolling, asymmetric rolling and asymmetric cryorolling were characterized by subjecting it to the tensile test and the microhardness test. The evolution in the microstructure was studied using scanning electron microscopy, transmission electron microscopy as well as energy dispersive X-ray spectrometry. Results show that the Ti-6Al-4V alloy sheets subjected to asymmetrical cryorolling with low rolling speed ratio between the upper and lower rolls have the highest tensile strength and microhardness. The tensile stress of the alloy samples after cold rolling was found to be 1008 MPa, 1046 MPa after asymmetric rolling, and 1113 MPa after asymmetric cryorolling. The highest Vickers hardness (HV395) is achieved by asymmetric cryorolling. We discuss the mechanical behavior using the criteria of grain size, size of second phase as well as dislocation density. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V alloy having a heterogeneous microstructure composed of ultrafine‐equiaxed‐α‐grains and fine‐lamellar‐α‐grains is investigated for microstructural changes during superplastic deformation at temperature of 700 °C. The Ti–6Al–4V alloy having an optimum fraction of fine‐lamellar‐α‐grains exhibits an excellent superplastic property and the highest elongation of 583% (tested at 700 °C 10−3 s−1). This is mainly due to the optimized activation of grain‐boundary‐sliding and additional accommodation mechanism associated with frequent occurrences of dynamic recrystallization and β precipitation at boundaries during deformation of the heterogeneous starting microstructure. The present result suggests the possibility that optimizing the starting microstructure so as to have an optimum heterogeneous‐microstructure serves as an additional stress accommodation mechanism and leads to a large superplastic elongation. [ABSTRACT FROM AUTHOR]

Titanium alloys stand out primarily due to their high specific strength and excellent corrosion resistance, they have higher mechanical strength to weight ratio but are 40% lighter than steel. It is widely used in aero-engines, gas turbines and aero-space structures and titanium products increased during the last decade. However, it is well known that titanium alloy is difficult to be formed at room temperature. Therefore, hot stretch bending (HSB) process was developed to create bent parts of extruded Ti-6Al-4V titanium alloy profile, thus reducing the cost impact of raw material and finished machining. In the present paper, a new force-controlled electric heating rotary stretch bending (HRSB) process was developed. In order to obtain the precise bending of titanium alloys extrusion, experimental investigations for extruded Ti-6Al-4V Alloy profile with T-section are carried out. Firstly, experimental method of HRSB and electric heating tension are proposed. Secondly, the HRSB process of Ti-6Al-4V Alloy extrusion at different forming temperatures and tension forces was investigated. Lastly, microstructures of Ti-6Al-4V Alloy formed in different conditions are investigated using SEM, TEM and EBSD method. The results show that: (1) When initial temperature of Ti-6Al-4V titanium alloy profile ranges from 700 to 750 ° C, and temperature of die surface ranges from 100 to 200 ° C, the forming quality and precision are higher. (2) Increasing post-stretching force can reduce the angle springback of Ti-6Al-4V titanium alloy profile. The results may help to provide the basis for the determination and optimization of hot stretch bending of Ti-6Al-4V titanium alloy profile. [ABSTRACT FROM AUTHOR]

The mechanical properties are impacted by the surface condition of metals. Titanium alloy is oxidized and diffused oxygen into substrate, leading to phase transition in an atmosphere with oxygen. The alpha-case kinetics and tensile behavior of Ti-6Al-4V alloy by high temperature oxidized in different phase regions were investigated by static oxidation test over the temperature range of 850-1100 °C and tensile tests over the temperature range of 830-950 °C. The relationship between high temperature plasticity, oxidation and microstructural transformation of titanium alloy was analyzed by metallographic method, hardness measurements and scanning electron microscopy. The results showed that the inward diffusion of oxygen was the reason of alpha-case generation, which modified the different effects at the surfaces of titanium in different phase regions. The cracks were observed at the surface of the specimens whose depths were greater at higher temperatures. The thickness of this alpha-case was increasing with elevated temperature. Under the high strain rate, the lower stress value of the thermally oxidized Ti-6Al-4V alloy in the vicinity of yielding point was observed compared with that unoxidized. The fractographic appearances of specimens oxidized were brittle and sharp type, while the fracture mode of specimens was ductile fracture without alpha-case. The higher amount of oxygen in α phase both stabilized α phase forming a microstructure and strengthened the α phase via solid solution strengthening. The existence of alpha-case led to easier surface crack initiation and propagation under the tension stress state. [ABSTRACT FROM AUTHOR]

Generally, torsion deformation has been recognized as a method of severe plastic deformation (SPD) to obtain a higher shear strain. The effect of strain reversal on the microstructure and mechanical properties was investigated using commercially Ti-6Al-4V alloy by twisting the rods with different effective strain amplitude, such as 180#x00B0;, 270#x00B0;, 360#x00B0; and 450#x00B0; per half cycle. In this work, the microstructure evolution and fracture morphology were carried out by a scanning electron microscope (SEM) and transmission electron microscope (TEM). An Instron 3382 was used for determining ultimate compression strength (UCS). The results show that UCS is very sensitive to cyclic forward-reverse torsion (CFRT) processing and increase distinctly after pre-CFRT. And the value of UCS reaches maximum at 180#x00B0; per half cycle. Besides, monotonic torsion (MT) by twisting the rods in one direction until the fracture occurs was also compared with CFRT. It is found that the ability of work hardening and accumulation of plastic strain is higher for CFRT as compared to MT, which is due to the latticed dislocation in the interior of the grains under CFRT deformation. Grain refinement and fracture feature were discussed to reveal the deformation mechanism of CFRT and MT. The discussion of microstructure evolution and strengthening mechanisms will provide a view to extrapolation to larger strains, finer structures and larger stresses. [ABSTRACT FROM AUTHOR]

The evolution of structure and strength properties of the Ti-6Al-4V alloy is investigated after helical rolling and subsequent groove rolling and annealing. It is shown that most significant structure refinement occurs in a material after sequential rolling treatments. In the rolled state the material achieves its maximum strength properties comparable to those of the alloy in an ultrafine-grained state. The structure and strength properties are observed to be stable up to the annealing temperature 873 K, which is 40 K higher than those in the ultrafine-grained alloy. The applicability of helical rolling and subsequent groove rolling followed by annealing is discussed in terms of improvement of the Ti-6Al-4V alloy properties. [ABSTRACT FROM AUTHOR]

This study reported the effect of the high-energy pulse current on the mechanical properties and microstructure evolution of Ti-6Al-4V alloy in the compression deformation process. The electroplastic compression (EC) of Ti-6Al-4V alloy was performed with discharge voltages of 50 and 70 V and strain rates of 0.01 and 0.03 s, respectively. The results show that the mechanical properties of Ti-6Al-4V alloy greatly change under the influence of the high-energy pulse current. Metallographic examination and x-ray diffraction are performed to observe the microstructural evolution of the alloy. An obvious dynamic globularization occurs at the later stage of the EC process even though the temperature of the samples is relatively low. An α- β phase change also occurs during the EC process. The microstructural evolution of Ti-6Al-4V alloy during the EC process is mainly attributed to the thermal and athermal effects of electropulsing, which promotes the dislocation motion and nucleation rate of dynamic globularization. [ABSTRACT FROM AUTHOR]

A Ti-6Al-4V alloy was used to examine the effect of martensitic (αʹ) or lamellar (α + β) microstructures on grain refinement and the hcp to fcc phase transformation during HPT processing. There was significant grain refinement with grain sizes of ~ 30 and ~ 40 nm in the αʹ and α + β microstructures, respectively, and with the occurrence of an allotropic hcp to fcc phase transformation in the αʹ sample after HPT. A high volume fraction of boundaries, together with a substructure containing initial defects of the martensitic sample, promotes the formation of the fcc phase during the HPT processing. [ABSTRACT FROM AUTHOR]

This study was conducted to examine the influence of the scanning speed of an electron beam on the fundamental properties of Ti-6Al-4V alloy produced by EBM (electron beam melting) method. We further investigated the effect of short-time heat treatment on those properties. By increasing the scanning speed, the desired outer shape was more closely achieved. However, molding defects became larger and the density reduced. On balance, the appropriate range of scanning speed was between 1 and 2 m/s. EBM materials had columnar microstructures elongated in the building direction. Although these characteristic microstructures were mainly composed of the stable α and β phases, the α' phase was partially generated at high scanning speed. By increasing the scanning speed, the amount of the α' phase increased and the hardness rose. The short-time heat treatment generated the fine α' and α phases in the prior β phase. This microstructural change markedly increased the hardness of EBM material. [ABSTRACT FROM AUTHOR]

In the present study, sub β-transus static annealing was carried out on a (α+β)-warm-rolled (700 °C, 90% thickness reduction) Ti-6Al-4V alloy at 900 °C for various durations (15, 30, 45, 60, 75 and 90 min). The key observation was that the spheroidization response of the constituent α-colonies from the starting warm-rolled material differs significantly during subsequent (α+β)-annealing treatment. While some of the α-colonies underwent an early morphological conversion from lamellar to equiaxed, some others stayed stable for prolonged durations. This unique phenomenon has been examined, for the first time, from an orientation perspective by coupling slip activation, boundary formation, and interfacial energy anisotropy of individual α-colonies with their response to static spheroidization. Orientation of the α-colonies in reference to the loading directions dictate the nature of slip activation (single versus multiple slip; basal or prism slip plus pyramidal 〈c+a〉 slip) during prior (α+β)-rolling. During subsequent static (α+β)-annealing, this factor translates into the relative ease of boundary splitting and thermal grooving for them. Formation of longitudinal boundaries, then set the order of spheroidization for diffusion based coarsening processes during long term annealing. Anisotropy in interfacial energy, owing to the loss of coherency during prior deformation (warm-rolling), creates further orientation dependency in the spheroidization sequence. An immediate consequence of this orientation dependent spheroidization response is realized in the formation of the macro-zones for two-phase Titanium alloys after secondary thermomechanical processing. Some remedial processing strategies are highlighted therein. [ABSTRACT FROM AUTHOR]

In the present study, experimental investigations of fiber-laser-beam-welding of 5 mm thick Ti-6Al-4V alloy are carried out based on statistical design of experiments. The relationship between the process parameters such as welding power, welding speed, and defocused position of the laser beam with the output responses such as width of the fusion zone, size of the heat affected zone, and fusion zone area are established in terms of regression models. Also, the most significant process parameters and their optimum ranges are identified and their percentage contributions on output responses are calculated. It is observed that welding power and speed plays the major role for full penetration welding. Also, welding power shows direct effect whereas welding speed shows the inverse effect on the output responses. The bead geometry is influenced by the defocused position of the laser beam due to the change in power density on the workpiece surface. However, overall fusion zone area is unaffected. Mechanical characterization of the welded samples such as microstructural analysis, hardness, and tensile tests are conducted. It is noticed that the hardness value of the FZ is higher than the HAZ and BM zone due to the difference in cooling rate during welding which promotes the formation of α′ martensitic phase in the FZ. Also, an average hardness value in the FZ is compared for two different defocusing positions (i.e. 1 and 2 mm). It is found that hardness value is higher for 1 mm defocused position than 2 mm due the decrement in grain size below a critical range at 2 mm defocused position. The ultimate tensile strength and % elongation of the welded samples are degraded as compared to BM which can be further improved by post heat treatment. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V alloy was subjected to heat treatment with (w/) and without (w/o) ultrasonic nanocrystalline surface modification (UNSM) treatment. The diffraction peaks of heat treatment w/o UNSM treatment samples were shifted to higher angles due to the tensile stress, while the heat treatment w/ UNSM treatment samples led to the intensity reduction and broadening, and the shift to lower angles, which may be attributed to the compressive residual stress, which increased with increasing the temperature. However, the peaks of heat treatment w/ UNSM treatment sample at 400 °C were shifted to higher angles. This unusual behavior of the alloy is associated with a high tensile stress of α phase. [ABSTRACT FROM AUTHOR]

Due to the nature of the near-net-shape formed of Ti-6Al-4V alloy produced by vacuum plasma spray forming (VPSF), post-deposition heat treatment is necessary to achieve to the superior mechanical and physical properties. In this study, transient liquid phase (TLP) bonding of VPSF and forging Ti-6Al-4V alloy were investigated. Simultaneous joining process under equi-axed α phase heat treatment cycle was performed to achieve to a suitable microstructure and mechanical properties of both bonding area and parent metal. Different thicknesses of 2, 5, 10, and 25 μm copper interlayer were used and the effect of the interlayer thickness was evaluated. Results showed that the joint region was wider in the TLP bonded VPSF alloy compared to the forged alloy under the same bonding conditions because of the higher diffusion rates in the VPSF alloy. The highest bonding shear strength was achieved for 2 μm interlayer thickness. It was 452 and 492 MPa for the TLP bonded VPSF and forged alloy, respectively. Increasing the interlayer thickness resulted in decreasing the bonding strength and increasing the hardness of the joint area due to the existence of Ti 2 Cu intermetallic compounds. The fracture analysis showed the brittle behavior due to the existence of the intermetallic compounds. [ABSTRACT FROM AUTHOR]

Fluorine doped diamond-like carbon (F-DLC) coatings were deposited on Ti-6Al-4V alloy using a hollow cathode plasma immersion ion implantation deposition system. The aim of this work is to investigate the influence of F content on the surface morphology, structure, mechanical and tribological properties (under air and stroke-physiological saline solution) of the F-DLC coatings. The results reveal that the ratio of H/fE instead of H/E can be well predicting the anti-wear results when the F-DLC coatings have enough adhesion strength, where H is hardness, E is Young's modulus and f is friction coefficient. The F-DLC coatings with high F content exhibit excellent tribological property under air. The low F content F-DLC coatings present super-low friction coefficient and wear rate in stroke-physiological saline solution. Reasons for the tribological property are proposed in combination with the films' morphology and mechanical property. [ABSTRACT FROM AUTHOR]

Titanium alloys are increasingly used for structural applications in transportation engineering (aerospace, automotive, railway, marine industry) because of their interesting properties (high mechanical properties to weight ratios, excellent corrosion resistance). In the present research work, the very high cycle fatigue behaviour of Ti–6Al–4V alloy of both bimodal and basketweave microstructures were investigated and compared. Fatigue tests at a very high number of cycles with R = −1 were carried out on titanium alloy - grade 5 specimens, cut from a forged flange used on a commercial aircraft. The experimental tests showed that this alloy has an always decreasing S-N curve, even for a number of cycles greater than 10 9 . It is the typical behavior of some alloys used in the aircraft industry, such as aluminum, titanium, nickel and high-strength steels. Moreover the very high cycle fatigue tests demonstrated that the Ti–6Al–4V alloy with bimodal microstructure has fatigue strength higher than the Ti–6Al–4V alloy with basketweave microstructure. The effect of microstructure on fatigue mechanism focused on internal crack initiation has been discussed through SEM observation of sub-cracks underneath the fracture surface. The temperature evolution during the tests was detected by means of IR cameras to study the temperature effect on the material response. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V alloy and commercially pure aluminum, which are commonly used in aerospace, medical, and automotive industries, are bonded by diffusion welding. Different welding parameters (560, 600, and 640 °C--0, 45, and 60 min--under argon shielding) are used in this process to make the materials more applicable in the industry. Here, the effects of parameters on the strength of joints were studied. The bonded samples were subjected to microhardness and tensile tests in order to determine their interfacial strength. The hardness values were found to decrease with increasing distance from the interface on the titanium side while it remained constant on the aluminum side. Maximum tensile strength was taken from the maximum bonding temperatures of 600 and 640 °C. A morphology examination of the diffusion interfaces was carried out with scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti-6Al-4V samples were bonded together using Cu coatings and Sn interlayers. The bonding of titanium samples was successful at various temperatures (700-950 °C) which are below the β-transus temperature of Ti-6Al-4V alloy. An applied uniaxial pressure of 1 MPa and a short bonding time of 15 min were selected as bonding parameters. Scanning electron microscope and energy-dispersive spectroscopy showed that the dissolution of Ti in the joint region increases with the increase in bonding temperature. X-ray diffraction analysis of the fractured surfaces revealed that SnTi, SnTi and SnTi intermetallic compounds (IMCs) were formed and dominated the joint structure. The shear strengths of the bonds increase with the increase in bonding temperature and reaches a maximum of 478 MPa for bond made at 950 °C. The microhardness analysis of the fractured surfaces compared to the base alloy confirmed the presence of the IMCs. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Ti at the top surface of the fractured bonds made at 700 °C which confirmed a successful joint evolution even at the lowest bonding temperature used. Atomic force microscopy observations for bonds made at 700 and 950 °C coincide with the XRD and XPS analysis and were able to reveal the remaining Cu particles on the substrates. [ABSTRACT FROM AUTHOR]

The main purpose of this paper was to investigate the effects of the different frequencies and loads of multi-pass ultrasonic surface rolling (MUSR) on surface layer mechanical properties, microstructure and fretting friction and wear characteristics of HIP (hot isostatic pressing) Ti–6Al–4 V alloy. Some microscopic analysis methods (SEM, TEM and EDS) were used to characterize the modified surface layer of material after MUSR treatment. The results indicated that the material in sample surface layer experienced a certain extent plastic deformation, and accompanied by some dense dislocations and twins generation. Moreover surface microhardness and residual stress of samples treated by MUSR were also greatly improved compared with the untreated. The fretting friction and wear properties of samples treated by MUSR in different conditions are tested at 10 and 15 N in dry friction conditions. It could be found that friction coefficient and wear volume loss were significantly declined in the optimal result. The main wear mechanism of MUSR-treated samples included abrasive wear, adhesion and spalling. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V alloy is widely used in many industries due to its outstanding properties. However, it has poor machinability using conventional mechanical cutting process. Electrical discharge machining is an alternative competitive process to machine titanium alloy by electrical erosion. This article studies the machining characteristics of Ti–6Al–4V with Cu–SiC composite electrode. Surface topography, subsurface microstructure, energy dispersive spectroscopy analysis, and micro-hardness have been analyzed. The machined surfaces show irregular compound structures, droplets of debris, shallow craters, and micro-pores. The surfaces processed by Cu–SiC electrode have fewer number of microcracks compared with that by Cu electrode. Continuous and uniform hardened layer can be achieved by Cu–SiC electrode. The hardened layer has significantly higher hardness than the bulk material because the new phases of TiC and TiSi 2 were created on the surface. [ABSTRACT FROM AUTHOR]

Recent advances in hip replacements are focused towards producing reliable bearing surfaces to enhance their longevity. In this perspective, progressive attempts have been made to improve the wear resistance of polyethylene to eliminate osteolysis and mechanical reliability of brittle alumina ceramics, but in vain. It is proposed that both high wear resistance and mechanical reliability can be retained if a thin layer of dense alumina is formed onto high toughness Ti-6Al-4V alloy. For this purpose, we devised a unique methodology in which a layer of Al metal was deposited onto the Ti alloy substrate by cold spraying (CS), followed by a heat treatment to form Al 3 Ti reaction layer at their interface to improve adhesion and subsequent micro-arc oxidation (MAO) treatment to transform Al to alumina layer. An optimal MAO treatment of cold sprayed Al formed an adherent and dense α-alumina layer with high Vickers hardness matching with that of sintered alumina used as a femoral head. Structure-phase-property relationships in dense α-alumina layer have been revealed and discussed in the light of our research findings. The designed alumina/Ti alloy hybrid might be a potential candidate for reliable bearing surfaces of artificial hip joint. [ABSTRACT FROM AUTHOR]

Medical-grade alloys, such as Ti-6Al-4V, have been used for fixation of fractured bone and for the total replacement of defective bone. Their bioactivity could be improved by applying a bone-like apatite layer onto their surfaces. This, in turn, enhances their integration with the surrounding tissues upon implantation. In addition, the presence of a bioactive bone-like coating minimizes the likelihood of corrosion. Various methods are known for the formation of apatite coating onto Ti-6Al-4V, among which sputtering has shown its promise as a simple direct method. In the current work, a sputtering technique was used to develop a 300 nm-thick bone-like apatite layer onto Ti-6Al-4V. Structural composition, integrity and morphology of the as-coated and thermally treated coatings were investigated. Coated substrates were further evaluated after soaking them in a simulated body fluid (SBF) for up to 14 days. Results showed the formation of an amorphous apatite layer onto the alloy, that was further shown to partially crystallize upon heat treatment. As a result of SBF treatment, the apatite layer was found to remodel through a dissolution-precipitation mechanism due to its amorphous and non-stoichiometric nature, forming a smooth layer with better homogeneity and decreased surface roughness. Electrochemical analysis of the coated alloys showed the enhanced corrosion protection of the alloy surfaces by coating them with apatite. In addition, pre-grinding of the alloy surfaces before the formation of the coating was also found to improve the corrosion inhibition of the alloy surfaces in aqueous media. [ABSTRACT FROM AUTHOR]

There is studied the technology of processing Ti-6Al-4V powder material with various initial densities using the method of equal channel angular pressing. The device with the 90, 120 and 135 degree angled joint channels was used for the study. The deformation was carried out at the room temperature. It was found that the most favorable stressed-and-strained state was formed in the instrument where the angle of channel joints was equal to 135 degrees. The maximum compression in the instrument is reached at 90 degree angle of the channel joints, but it needs a larger deformation force. To obtain pressed material it is recommended to use a high ECAP cycle for any configuration. [ABSTRACT FROM AUTHOR]

Pulsed plasma arc additive manufacturing (PPAM) is a novel additive manufacturing (AM) technology due to its big potential in efficiency, convenience and cost-savings comparing with other AM process. In this research, several Ti-6Al-4V thin walls were deposited by an optimized weld wire-feed PPAM process, in which the heat input was gradually decreased layer by layer. The deposited thin wall consisted of various morphologies with different microstructure, such as epitaxial growth of prior β-grains, martensite and horizontal layer bands of Widmanstätten, which depend on the heat input, multiple thermal cycles and gradual cooling rate in the deposition process. Reducing heat input of each bead and using pulsed current in the PPAM process, the microstructure of thin wall was refined. Meanwhile, the thin wall was strengthening and toughening. The average yield strength (YS) and ultimate tensile strength (UTS) reach 909 MPa and 988 MPa, respectively, and elongation reaches about 7.5%. The thin wall exhibited excellent performance in the aeronautical applications owing to the high values of mechanical properties in the room temperature. [ABSTRACT FROM AUTHOR]

This study investigated the effects of wet peening treatment on the fretting fatigue behavior and crack propagation in Ti–6Al–4V alloy. Wet peening induced a compressive residual stress at 0–160 μm depth and enhanced the hardness at 0–80 μm depth. Results of the fretting fatigue tests show that the fretting damage could efficiently reduce the fatigue life of both the un-peened and wet peened samples. Moreover, wet peening could effectively increase the fretting fatigue resistance. Investigation on crack propagation mechanism revealed that the increased resistance is due to the synergistic effect of the enhanced hardness and the induced compressive residual stress in the wet peening modified layer. The enhanced hardness could resist the local fatigue in the fretting cracking stage and the compressive residual stress could retard crack growth. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V alloy is widely used in superplastic forming process. The conventional conditions require high forming temperatures ( T ≥ 900 ° C ) and low strain rates ( ε ̇ ≤ 10 − 3 s − 1 ). In order to reduce the costs of the industrial process, recent investigations focus on the micro-structural refinement of the material. It allows an improvement of the forming conditions which makes lower forming temperatures and higher strain rates eligible whereas low strain rates ( ε ̇ ≤ 10 − 3 s − 1 ) and high temperatures ( T ≥ 800 ° C ) are particularly suitable for conventional superplastic forming conditions. However, the mechanical response of the Titanium alloy strongly depends on the starting micro-structure considered and on its evolution with the temperature and the deformation. The objective of the present investigation is to observe the micro-structural evolutions of Ti–6Al–4V alloy under thermal and mechanical loadings from different starting micro-structures. Hence, an internal grain growth variable is identified by the use of these observations. Then, it is introduced into the behavior model and its influence on the mechanical response of the material is analyzed. The final constitutive equations are able to take into account viscosity, strain hardening and grain size evolution for a wide range of strain rates and forming temperatures ( 10 − 4 s − 1 ≤ ε ̇ ≤ 10 − 2 s − 1 ; 650 ° C ≤ T ≤ 870 ° C ). Moreover, the model is able to consider several starting microstructures (different initial grain sizes) and to predict their influence on the viscous flow and the strain hardening. At last, some model verifications are conducted to check the validity of the non-isothermal model formulation. Some predictions are also performed by considering several starting microstructures. [ABSTRACT FROM AUTHOR]

The microstructure evolution of Ti-6Al-4V alloy induced by wet peening treatment was studied in this work. The results show that the dislocation interaction dominates the grain refinement process. The modified layer could be divided into reconfiguration regime, unstable regime and metastable regime with depth. Corresponding to the characteristic curve of residual stress field, the maximum of compressive residual stress locates in the unstable regime and the dislocation annihilation and rearrangement lead to the decrease of the compressive residual stress in the near surface layer. [ABSTRACT FROM AUTHOR]

The present article evaluates the influence of independent control factors such as percentage of primary alpha phase, impact velocity, impingement angle, and erodent size on solid particle erosion behavior of Ti-6Al-4V alloy using a statistical approach. Microstructural variation in terms of different percentage of primary alpha phase of investigated alloy has been introduced by solution annealing it at different temperatures followed by thermal aging. Solid particle erosion tests have been carried out using a sand blast–type test rig following an experimental schedule based on Taguchi's orthogonal arrays. It is observed that erosion rate and the value of percentage elongation decreased with an increase in the content of primary alpha phase from 10 to 20% and then increased for the value corresponding to the content of 30% primary alpha phase in this alloy. We observed that the solid particle erosion behavior of the investigated alloy consisting of various percentages of primary alpha phase is related to their ductility. Among all four control factors, impact velocity of the erodent has been found to be the most significant control factor influencing the solid particle erosion behavior of this alloy followed by impingement angle, percentage of primary alpha phase, and erodent size. Impact velocity has greatest static influence of 91.35%, impingement angle has an influence of 4.69%, percentage of primary alpha phase has an influence of 2.28%, and erodent size has an influence of 0.42% on solid particle erosion having R2 = 0.99. Material loss during solid particle erosion of this alloy was found to be ductile in nature. Ploughing or pile-up leading to platelet formation is the primary mechanism of material loss during erosion of the alloy. [ABSTRACT FROM AUTHOR]

In many hip replacement surgeries, monolithic alumina is used as a femoral head due to its high wear resistance. However, it is liable to fracture under load bearing operations in artificial joints. We propose a promising way to overcome this limitation by forming a dense alumina layer onto a relatively tough substrate such as Ti–6Al–4V alloy to obtain high wear resistance on a material that can sustain relatively high toughness. For this purpose, Al metal powders were deposited onto Ti–6Al–4V alloy by cold spraying in N 2 atmosphere. Interfacial adhesion between Al and the Ti alloy was improved by the formation of a reaction layer of Al 3 Ti between them by heating at 640 °C for 1 h in air. Subsequently, micro-arc oxidation treatment was performed to oxidize Al. The oxidized layer was composed of an outer porous layer of γ-alumina and inner-most dense layer of α-alumina. The α-alumina layer was almost fully densified and exhibited high Vickers hardness almost equal to that of alumina ceramics used as the femoral head. Thus, the newly developed dense alumina/Ti alloy can be potentially used to produce the reliable bearing surfaces of artificial hip joint. [ABSTRACT FROM AUTHOR]