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This study presented an analysis of four failed implants removed from three human patients. The implants were in situ for 3 to 13 months and were removed due to pain, mobility, or infection, and fixed by immersion in 10% formalin. The specimens were embedded in PMMA, sectioned, and stained with basic fuchsin and toluidine blue. The specimens disclosed a coronal/apical variation of tissue responses. Apical sections of those implants with attached bone showed acceptable bone adaptation to the implant with little or no intervening connective tissue. As these sections progressed coronally, the intervening connective tissue widened, became loosely arranged, and aligned parallel to the implant surface. The most coronal aspect of the bone core showed necrosis, ulceration, and hemorrhage. It is speculated that trauma from insertion and failure of vascular regeneration may be the causes of failure. [ABSTRACT FROM AUTHOR]

Metallurgical characteristics in the machined surface layer can be modified due to suffering the localized thermo-mechanical stresses during high-speed machining. Plastic deformation is generated by the localized thermo-mechanical stresses. The depth of plastic deformation will then influence the functional performances and service life of the machined components. However, the available tool life is diminished due to rapid tool wear in machining titanium alloy. The tool wear induces additional thermo-mechanical stresses on the tool-workpiece interface, which results in deeper plastic deformation. This article proposed a prediction model of the plastic deformation depth induced by the coupled thermo-mechanical stress considering tool flank wear. The proposed model can effectively predict the depth of plastic deformation at different tool flank wear stages. This prediction model is verified with the high-speed turning experiments of Ti-6Al-4V. It is demonstrated that there is a better consistency between the measured and predicted results with the error interval of 11.2% to 15.4%. The results indicated that the tool flank wear should be limited in an appropriate value from the perspective of the depth of plastic deformation. This work can be used to guarantee the machined surface integrity during machining Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

Introduction: In this study, the super-long deep-hole drilling of a titanium alloy was investigated. Methods: According to material properties of the titanium alloy, an experimental approach was designed to study three issues discovered during the drilling process: the hole-axis deflection, chip morphology, and tool wear. Results: Based on the results of drilling experiments, crucial parameters for the super-long deep-hole drilling of titanium alloys were obtained, and the influences of these parameters on quality of the alloy’s machining were also evaluated. Conclusions: Our results suggest that the developed drilling process is an effective method to overcome the challenge of super-long deep-hole drilling on difficult-to-cut materials. [ABSTRACT FROM AUTHOR]

The research presented in this paper investigated the effects of spindle speed and feed rate on the resultant cutting forces (thrust force and torque) and temperatures while drilling SawBones ® biomechanical test materials and cadaveric cortical bone (bovine and porcine femur) specimens. It also investigated cortical bone anisotropy on the cutting forces, when drilling in axial and radial directions. The cutting forces are only affected by the feed rate, whereas the cutting temperature in contrast is affected by both spindle speed and feed rate. The temperature distribution indicates friction as the primary heat source, which is caused by the rubbing of the tool margins and the already cut chips over the borehole wall. Cutting forces were considerably higher when drilling animal cortical bone, in comparison to cortical test material. Drilling direction, and therewith anisotropy, appears to have a negligible effect on the cutting forces. The results suggest that this can be attributed to the osteons being cut at an angle rather than in purely axial or radial direction, as a result of a twist drill's point angle. [ABSTRACT FROM AUTHOR]

Titanium alloy has gained acceptance in the aerospace, marine, chemical, and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-BC composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epitaxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432 ± 27, while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360 ± 18. From the hardness results obtained, ceramic BC has improved the mechanical properties of the primary alloy. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloys are difficult-to-cut materials that have extensive applications in the automotive and aerospace industry. A great deal of effort has been made to develop and improve the machining operations of Ti6Al4V alloys. This paper presents an experimental study that systematically analyzes the effects of the machining conditions (ultrasonic power, feed rate, spindle speed, and tool diameter) on the performance parameters (cutting force, tool wear, overcut error, and cylindricity error), while drilling high precision holes on the workpiece made of Ti6Al4V alloys using rotary ultrasonic machining (RUM). Numerical results were obtained by conducting experiments following the design of an experiment procedure. The effects of the machining conditions on each performance parameter have been determined by constructing a set of possibility distributions (i.e., trapezoidal fuzzy numbers) from the experimental data. A possibility distribution is a probability-distribution-neural representation of uncertainty, and is effective in quantifying the uncertainty underlying physical quantities when there is a limited number of data points which is the case here. Lastly, the optimal machining conditions have been identified using these possibility distributions. [ABSTRACT FROM AUTHOR]

The near-β titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) fabricated by laser additive manufacturing was further annealed by multiple low temperature aging heat treatments. Microstructures and fracture surfaces were observed by optical and electron microscopes. Brittle tensile fracture behaviors were analyzed and cleavage fracture and quasi-cleavage fracture were distinguished. Results show that athermal ω phases in Ti-55511 have negligible strengthening effect because of their very small sizes and low content. With the aid of age hardening heat treatment, nano-scaled α phases precipitate, leading to higher microhardness. But the tensile properties of Ti-55511 did not effectively improve because brittle fracture happens due to the precipitation of nano-scaled α phases, which have similar sizes with brittle ω phases. The brittle fracture behavior is more relevant to α phase sizes instead of their volume fractions. With aging temperature increasing, the sizes of nano-scaled α phases increase and the alloy brittleness slightly decreases. [ABSTRACT FROM AUTHOR]

A study based on uniaxial tension tests were conducted in this paper to understand the hot deformation behaviors of TA32 alloy during superplastic deformation at a deformation temperature of 915 °C and an initial strain rate of 6.64×10 −3 s −1 . In the test, the maximum fracture elongation reached 1065%, exhibiting good superplastic deformation ability. Electron back-scattered diffraction (EBSD) was used to analyze and study evolution of microstructures and textures in the process of deformation with the following findings: During tensile deformation, the fraction of low-angle grain boundaries (<15 °, LAGBs) decreased drastically, while that of high-angle grain boundaries (≥15 °, HAGBs) increased from 45% to 96.2%. As the further straining, the role of continuous dynamic recrystallization (CDRX) was weakened, while that of discontinuous dynamic recrystallization (DDRX) was strengthened. Dynamic recrystallization helped refine coarse grains in the initial structures and reduced deformation defects in grains. The superplastic deformation mechanism of TA32 alloy was dominated by boundary sliding of high-angle grains, coordinated by dislocation motion at the softening stage and by grain rotation at the steady deformation stage respectively. In addition, the drawing force contributed to both dynamic recrystallization and rotation of grains. [ABSTRACT FROM AUTHOR]

MANY TITANIUM ALLOYS AND EVEN MATERIALS such as concrete exhibit a nonlinear relationship between strain and stress, when the strain is small enough that the square of the norm of the displacement gradient can be ignored in comparison to the norm of the displacement gradient. Such response cannot be described within the classical theory of Cauchy elasticity wherein a linearization of the nonlinear strain leads to the classical linearized elastic response. A new framework for elasticity has been put into place in which one can justify rigorously a nonlinear relationship between the linearized strain and stress. Here, we consider one such model based on a power-law relationship. Previous attempts at describing such response have been either limited to the response of one particular material, e.g. Gum Metal, or involved a model with more material moduli, than the model considered in this work. For the uniaxial response of several metallic alloys, the model that is being considered fits experimental data exceedingly well. [ABSTRACT FROM AUTHOR]

Most current analysis of nano-indentation test data assumes the sample to behave as an isotropic, homogeneous body. In practice, engineering materials such as structural steels, titanium alloys and high strength aluminium alloys are multi-phase metals with microstructural length scales that can be the same order of magnitude as the maximum achievable nano-indentation depth. This heterogeneity results in considerable scatter in the indentation load-displacement traces and complicates inverse analysis of this data. To address this problem, an improved and optimised inverse analysis procedure to estimate bulk tensile properties of heterogeneous materials using a new ‘multi-objective’ function has been developed which considers nano-indentation data obtained from several indentation sites. The technique was applied to S355 structural steel bulk samples as well as an autogenously electron beam welded sample where there is a local variation of material properties. Using the new inverse analysis approach on the S355 bulk material resulted in an error within 3% of the experimental yield strength and strain hardening exponent data, which compares to an approximate 9% error in the yield strength and an 8% error in the strain hardening exponent using a more conventional approach to the inverse analysis method. Applying the new method to indentation data from different regions of an S355 steel weld and using this data as an input into an FE model of the cross-weld, tensile data from the FE model resulted matching the experimentally measured properties to within 5%, confirming the efficacy of the new inverse analysis approach. [ABSTRACT FROM AUTHOR]

In this paper, a new model based on the Johnson-Cook fracture criterion is proposed to predict the ductility of Ti6Al4V titanium alloy sheets deformed at wide range of temperatures (25–900 °C) and stress states. Experiments were carried out and strain at fracture recorded on samples of different shapes to cover various loading conditions: uniaxial tensile, shear and equi-biaxial plane stress tension. The stress triaxiality and the deviatoric effect were evaluated through numerical simulations of these experiments. The original Johnson-Cook (J-C) fracture strain criterion was modified to incorporate a quadratic function of the stress triaxiality and a deviatoric parameter to represent different stress states. In the new formulation of the J-C criterion, a quadratic function of the temperature was also introduced to represent the transformation related ductility inherent in the two phase ( α / β phases) titanium alloy Ti6Al4V at elevated temperatures. The model was calibrated using as reference state the strain rate of 1 s −1 and temperature of 600 °C. The choice of 600 °C as reference was based on the rapid increase in the β phase and ductility above this temperature. The new ductile fracture criterion for elevated temperature sheet forming was finally validated using testing conditions different from those used in its derivation. [ABSTRACT FROM AUTHOR]

In the present study, uniaxial compression tests were employed between 1000 and 1100 °C under the strain rates of 10 −3 , 10 −2 and 10 −1 s −1 to investigate the hot deformation behavior of BT9 titanium alloy. Work hardening behavior interpretation and analytical investigations including calculation of deformation activation energy, and developing process maps were used to establish a numerical correlation between microstructural evolution and the flow behavior of the alloy. The results showed that dynamic recrystallization takes place at severe condition (T = 1000 °C and ε ˙ = 0.1 s −1 ), while dynamic recovery is the major microstructural mechanism at other condition. According to dynamic material model and Prasad's instability criterion, the maximum power dissipation of 52% and 46% occur at 1000 °C/0.1s −1 and 1150 °C/0.001 s −1 , respectively. Electron backscattered diffraction images and high resolution optical images also revealed that continuous dynamic recrystallization is the governing mechanism at these deformation conditions resulting in a significant grain refinement. Considering the calculated deformation activation energies, power efficiency domains and the microstructural observations, 1000 °C/0.1 s −1 was determined as the optimum deformation condition. [ABSTRACT FROM AUTHOR]

To develop microwave absorbing materials over X and Ku-band, M-type hexaferrites: BaCoxTixFe(12−2x)O19, with x varying from 0.0 to 1.0 in step size of 0.2, were prepared by solid state reaction route. Characterization techniques like x-ray diffraction, scanning electron micrograph and vibration sample magnetometer were used to analyze the crystalline phases, morphologies, and magnetic properties of the samples. Vector network analyzer was utilized to scrutinize the electromagnetic properties like complex permittivity, complex permeability, and microwave absorption. Results indicate the enhancement of imaginary permittivity and permeability with substitution. Absorption analysis concludes that the composition with x = 0.8 is the best single-layer microwave absorber out of all the prepared compositions with minimum reflection loss −33 dB at thickness of 3.1 mm. At the same time, the compositions x = 0.2, 0.4, 0.6, and 1.0 are combined to form double-layer absorber with absorption more than 99% in X and Ku-band. [ABSTRACT FROM PUBLISHER]

The special features inherent in the development of high-temperature deformation and structural evolution in materials are investigated, using a VT22 titanium alloy of the transition class (Ti - 4.74 mass% Al - 5.57 mass% Mo - 5.04 mass% V) subjected to helical rolling + aging as an example. This treatment is found to give rise to an intragrain fine acicular martensite structure with fine inclusions of α-phase particles of size ~1 μm. It is shown that in the alloy undergoing plastic deformation at temperatures approaching the polymorphic transformation temperature, the elongation to failure is in excess of 300%. The high plasticity of the alloy in the conditions considered is likely to be due to vigorous development of phase transformations and intensification of diffusion-controlled processes, including the effects of the evolution of the dislocation structure, growth of subgrains, and formation of new grains in the bulk of the pre-existing ones during plastic deformation. [ABSTRACT FROM AUTHOR]

This study investigates equilibrium-to-nonequilibrium solid phase transitions induced by MeV-scale electron irradiation in B2-CoTi and L12-Co3Ti intermetallic compounds by means of high-voltage electron microscopy. Under MeV-scale electron irradiation, B2-CoTi transforms into a body-centered cubic solid solution through chemical disordering and eventually transforms into an amorphous phase. The critical temperature for amorphisation is found to be 110 K. L12-Co3Ti also exhibits chemical disordering at temperatures below 700 K. However, its amorphisation does not occur even at a low temperature of 20 K. The dominant factor in these solid phase transitions is discussed in terms of the Gibbs free energy. [ABSTRACT FROM PUBLISHER]

Selective laser melting is an advanced manufacturing process which can control the microstructure evolution and mechanical properties of as-manufactured products via various processing parameters. In this study, the porosity/relative density, surface quality, microstructure and mechanical properties were investigated on the selective laser melted Ti-6Al-4V alloy specimens fabricated with a wide range of laser energy inputs. It was found that the microstructure of selected laser melted Ti-6Al-4V alloys is typical of acicular martensitesα′. Quantitative analysis reveals that the relative density, martensitic lath size and microhardness increase with the laser energy input. The surface quality is also substantially affected by the energy input. [ABSTRACT FROM PUBLISHER]

In titanium alloys, variant selection (VS) of grain boundary α (GB α ) at prior β grain boundaries (GBs) during α precipitation has a significant influence on the subsequent transformation pathway and transformation texture development of the α phase, and thus on the final mechanical properties. In this paper, we assess systematically the applicability of all current empirical rules for VS of GB α at prior β GBs using experimental characterization of GB misorientation, boundary plane inclination, and orientation relationships between the GB α and adjacent β grains in Ti-5553. We find that all these VS rules may be violated for a given β grain boundary. Based on the experimental observations, the frequencies of each of these empirical rules being either violated or followed have been assessed, and from this assessment, we analyze theoretically whether the arguments underlying each of these rules are physically sound and why rules are violated, and then discuss when a sound prediction may be made using these empirical VS rules. [ABSTRACT FROM AUTHOR]

The influence of cold plastic deformation on passivity of Ti-6Al-4V alloy (UNS R56400) was investigated by means of potentiodynamic polarization, Mott-Schottky analysis, atomic force microscopy, and scanning Kelvin probe force microscopy. The results showed that the cold working increased the passive current density. Mott-Schottky analysis revealed the n-type semiconducting behavior of the passive film. The donor density of the passive film was declined by increasing the film formation potential. On the other hand, work hardening increased the density of defects within the passive film, regardless of the applied potential. The Volta potential maps showed that a phase possesses lower surface potential compared to the β, i.e., 38.6 mV. The plastic deformation decreased the surface potential of both phases; however, the relative nobility of the constituent phases had been slightly affected by cold working, i.e., 5 mV. The topographic results after immersion of the alloy in an aggressive acidic environment revealed that the Volta potential difference between a and β was sufficient to make a more vulnerable to corrosion attacks. [ABSTRACT FROM AUTHOR]

Fatigue crack growth at room temperature and its relation to the local microstructure is studied for four different γ-TiAl-alloys with microstructures ranging from coarse and fully lamellar to fine and partly lamellar. It is shown that the number of cycles to failure depends strongly on the efficiency of the first barrier to crack extension, as crack growth rates may increase rapidly once this barrier has been breached by a specific crack. The crack extension behaviour for two typical barriers (colony boundary and twin boundary) is studied using high-resolution optical and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti–6Al–4V), CaO–SiO 2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO 2 and Y 2 O 3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular–dendrite structure to compact cellular crystal. The addition of CeO 2 or Y 2 O 3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO 3 , CaO, α-Ca 2 (SiO 4 ), SiO 2 and TiO 2 . Y 2 O 3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris–HCl solution, the samples doped with CeO 2 or Y 2 O 3 present a lower weight loss, indicating the addition of CeO 2 or Y 2 O 3 improves the degradability of laser cladding sample. [ABSTRACT FROM AUTHOR]

The phase equilibria in the Co–Ti–V ternary system have been investigated by means of optical microscopy (OM), electron probe microanalyzer (EPMA), differential scanning calorimetry (DSC), field emission scanning electron microscope (SEM) and X-ray diffraction (XRD). The mechanical properties were measured by compressive tests. Four isothermal sections of the Co–Ti–V ternary system at 800 °C, 1000 °C, 1100 °C and 1200 °C were experimentally established. The results show that: (1) there is no ternary compound in this system; (2) the CoTi2 phase and Co3Ti phase stabilized by the V addition; (3) a large solubility of Ti in the σ-Co2V3 phase was observed at all isothermal sections of 800 °C, 1000 °C, 1100 °C and 1200 °C; (4) The alloy with the distribution of fine cuboidal Co3Ti (L12) in (αCo) phase was observed. (5) The compressive strength of Co77.29Ti5.83V16.88 (at.%) alloy at room temperature was measured to be about 1985 MPa. The newly determined phase equilibria in this system will provide useful information for the development of Co-based and Ti-based materials. [ABSTRACT FROM AUTHOR]

Static coarsening is an important physical phenomenon that influences microstructural evolution and mechanical properties. How to simulate this process effectively has become an important topic which needs to be dealt with. In this paper, a new cellular automaton (CA) model, which considers the effect of solute drag and anisotropic mobility of grain boundaries, was developed to simulate static grain coarsening of titanium alloys in the beta-phase field. To describe the effect of the drag caused by different solute atoms on coarsening, their diffusion velocities in beta titanium were estimated relative to that of titanium atoms (Ti). A formula was proposed to quantitatively describe the relationship of the diffusion velocity of Ti to that of solute atoms; factors influencing the diffusion velocity such as solute atom radius, mass, and lattice type were considered. The anisotropic mobility of grain boundaries was represented by the parameter c, which was set to 1 for a fully anisotropic effect. These equations were then implemented into the CA scheme to model the static coarsening of titanium alloys Ti-6Al-4V, Ti17 (Ti-5Al-4Mo-4Cr-2Sn-2Zr, wt%), TG6 (Ti-5.8Al-4.0Sn-4.0Zr-0.7Nb-1.5Ta-0.4Si-0.06C, wt%) and TA15 (Ti-6Al-2Zr-1Mo-1V, wt%) in the beta field. The predicted results, including coarsening kinetics and microstructural evolution, were in good agreement with experimental results. Finally, the effects of time, temperature, and chemical composition on grain coarsening and the limitations of the model were discussed. [ABSTRACT FROM AUTHOR]

Abstract: The effect of treatment by high intensity pulse ion beam (HPIB) and compression plasma flow (CPF) with energy density greater than 10J/cm2 on the phase and element composition, microstructure, hardness and depth of modified layer of WC–TiC–Co hard alloy was investigated. It was found that the increase of short-pulse (9⁎10−2 µs) HPIB energy density (due to the increase of pulses number from 3 to 300) led to the fusion of tungsten and titanium carbides particles following to formation of (W1−x Ti x )C solid solution oversaturated by tungsten. The formation of great number of cracks inside of fused layer and inside of carbide particles allocated below fused layer takes place as a result of impact of power shock waves generated by HPIB at great number of pulses (100, 300). The higher duration (~100µs) of CPF pulse with the energy density of 13–40J/cm2 provides convective mixing of melt''s components and forms fused layer, the thickness of which reaches 8–10µm (40J/cm2). The hardness of the surface layer containing oversaturated (W1−x Ti x )C solid solution with the thickness of several microns exceeds the hardness of untreated hard alloy in 2 times. [Copyright &y& Elsevier]

In contrast to their exceptional mechanical properties, titanium and its alloys possess poor friction and wear characteristics. Nanocrystalline diamond (NCD) films appear to be a promising solution for their tribological problem due to their smooth surfaces and small grain size. However, the synthesis of a well adherent NCD film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work NCD thin films have been deposited on pure Ti substrates in a microwave plasma chemical vapor deposition (MWPCVD) reactor under fixed pressure and methane concentration in hydrogen but over a wide temperature range. The effects of depositing temperatures on the adhesion of films are evaluated using Rockwell indentation tests. It is found that by increasing the deposition temperature the films bonding deteriorates. The films synthesized are characterized by field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and X-ray diffraction. [ABSTRACT FROM AUTHOR]

We report the formation of self-organized Ti–Al–Zr alloy oxide nanotube arrays at different fluoride concentrations in formamide and glycerol electrolytes. The nanotube morphology is strongly influenced by the fluoride concentration, applied potential and reaction time. Titanium alloy (Ti–Al–Zr) oxide nanotube arrays with a length of about 6.13 μm, a pore diameter of 116 nm and wall thickness of 55 nm were prepared at 50 V for 24 h in formamide and glycerol mixtures (volume ratio 1:1) with addition of 1.0 wt% NH4F. The as-prepared nanotubes were amorphous and alloy oxide crystals appeared after annealing in air at 400 and 600 °C for 3 h. [ABSTRACT FROM AUTHOR]

Abstract: The quasi-static assemblies used in industrial applications are subjected to microsliding due to vibrations of variable amplitudes related to mechanical or aerodynamic instabilities. The titanium alloys used in such structures present extensive wear and must be protected by coatings. This article is devoted to the fretting behaviour of a coated Ti–6Al–4V alloy under free (un-imposed) displacement. The coating is made of a cupronickel alloy (CuNiIn or CuNiSi) topped by a polymer bonded solid lubricant MoS2. A fretting map was established to highlight the boundary between wear and seizure. An energetic coefficient of wear considering the global wear volume of the contact and the tribological parameters such as sliding distance and dissipated energy was established. Various morphologies of the third body observed in the contact were analyzed in terms of cohesion, ductility and adhesion. They were correlated to the tribological behaviour of the studied materials. [Copyright &y& Elsevier]

Abstract: Titanium and its alloys are currently in use as implant materials for orthopaedic surgery. These materials possess outstanding corrosion resistance due to a dense and passive oxide film on the surface. When these alloys are implanted in a living body, removal of surface material takes place because of mechanical wear and corrosion. Simultaneous chemical and mechanical effects also limit long-term use of such materials. The aim of the present study is to clarify the damage accumulation mechanism of Ti–6Al–4V alloys under the simultaneous reaction of corrosion and wear. For this purpose, we developed a new tribocorrosion system and then evaluated corrosion wear characteristics of the alloys with special attention focused on the effects of scratching rate on repassivation behavior. Two types of corrosion wear tests were carried out: one was the free corrosion potential measurement and the other was the potentiostatic polarization test both with simultaneous application of wear damage. In corrosion wear environment, a transition of wear type from abrasive to adhesive was observed with increase of the scratching rates. Higher scratching rate prevented regeneration of passive films on worn surfaces, resulting in generation of relatively large corrosion pits and a change in the wear mechanism. These results suggested that the scratching rate was an important factor affecting the damage accumulation process. [Copyright &y& Elsevier]

Abstract: Material superplasticity is a state in which solid crystalline material is deformed well beyond its usual breaking point, usually with the elongation greater than 200% in tensile test. Such a state is generally achieved under specific microstructure and deformation conditions. In superplastic deformation (SPD) process, strain-rate sensitivity exponent (m) is a critical parameter, which represents, articulates and quantifies the superplasticity level. The higher the m value, the better the superplasticity of the materials. In this paper, a totally novel concept of maximum m superplasticity deformation (MaxmSPD) is proposed and realized through simultaneous measurment of m value and concurrent control of deformation strain rate in such a way that the maximum m is always maintained in the deformation process, through dynamic control and adjustment of deformation strain rate. To prove and realize this concept, the MaxmSPD of Ti–6Al–4V titanium alloy is conducted. The experimental results show that without grain refinement processing, the superplasticity of Ti–6Al–4V alloy is significantly enhanced compared to conventional SPD process in which the deformation strain rate is kept constant. In details, the elongation for Ti–6Al–4V in MaxmSPD is increased from 421 to 523%. Furthermore, the elongation of Ti–6Al–4V at 900°C is 641%, which is almost double the value in conventional SPD process. Therefore, these interesting findings and the development of MaxmSPD not only simplify the requirements on grain refinement processing for SPD process, it also pioneers a totally new approach for realization of superplastic deformation and extends the application scenarios of SPD process. [Copyright &y& Elsevier]

Abstract: Fretting wear and fretting fatigue are two commonly observed material damages when two contacting bodies with a clamping load are under the oscillatory motion. In this study, fretting wear damage of Cu–Al coating on titanium alloy, Ti–6Al–4V substrate was investigated using the dissipated energy approach. Fretting tests were conducted with either no fatigue load or the maximum fatigue load of 300MPa and stress ratio of 0.1 on the substrate (specimen). In order to investigate the effect of contact load and contact size, different pad sizes and contact loads were used in the tests. Accumulated dissipated energy versus wear volume data showed a linear relationship regardless of fatigue loading condition on specimen with the smaller pad size. However, two separate linear relationships were observed based on the fatigue loading condition with the larger pad size, such that a relatively more dissipated energy was required for a certain amount of wear with fatigue load on the specimen. The linear relationship between the accumulated dissipated energy and wear volume for both pad sizes extended from partial to gross slip regimes and was not affected by the applied contact load. Further, fretting tests with and without fatigue load resulted in different shapes of fretting loops when the larger pad size was used. [Copyright &y& Elsevier]

Abstract: In this work, a Ti–48Al alloy was induction melted and allowed to cool and solidify in a ZrO2 based crucible with an inner layer of Y2O3, and the effect of superheating parameters (time and temperature) on the metal–crucible interface, alloy chemical composition, microstructure and microhardness is evaluated. Microhardness variation and segregation profiles of residual elements, namely yttrium and oxygen, from the surface to the inside of samples are presented and compared, in order to establish a relationship between the processing parameters, alloy contamination and the “alpha-case” extent. The alloy microstructure at the metal–crucible interface is characterized for each superheating time and temperature. The Y2O3 crucible layer was found to suffer some erosion and be slightly dissolved by the molten alloy and the extent of that dissolution, and consequent metal contamination with yttrium and oxygen, depend on both superheating temperature and holding time. A relationship was found between oxygen concentration profiles and microhardness profiles of the α2 +γ microconstituent, from the surface to the inside of samples, which depends on the superheating temperature, but is not affected by the holding time. [Copyright &y& Elsevier]

Abstract: The effect of Sn substitution for Cu on the glass-forming ability was investigated in Ti41.5Zr2.5Hf5Cu42.5−x Ni7.5Si1Sn x (x =0, 1, 3, 5, 7) alloys by using differential scanning calorimetry (DSC) and X-ray diffractometry. The alloy containing 5% Sn shows the highest glass-forming ability (GFA) among the Ti–Zr–Hf–Cu–Ni–Si–Sn system. Fully amorphous rod sample with diameters up to 6mm could be successfully fabricated by the copper mold casting Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy. The activation energies for glass transition and crystallization for Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 amorphous alloy are both larger than those values for the Sn-free alloy. The enhancement in GFA and thermal stability after the partial replacement of Cu by Sn may be contributed to the strong atomic bonding nature between Ti and Sn and the increasing of atomic packing density. The amorphous Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy also possesses superior mechanical properties. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the temperature reached during drilling of the titanium alloy Ti6Al4V, employing class K10 carbide drills with and without hard coating (TiAlN, CrCN or TiCN). The main object of this study was to evaluate the temperature for different coated tools under the condition of application of minimal quantity of lubricant (MQL). The drilling process was chosen to evaluate the effect of the lubrication obtained with MQL, where the lubricant was applied either with an external nozzle or internally through the drill. The results show potential for drilling with MQL applied internally through the tool. For drilling with MQL applied with an external nozzle, the process was restricted to small depths and limited with reference to the requirements of the surface quality of the hole. [Copyright &y& Elsevier]

Abstract: A titanium nitride (TiN) coating was deposited by magnetron sputter ion plating onto steel and titanium alloy polished substrates. The adhesion of the coating on each substrate material was investigated using a newly developed multimode scratch tester. Progressive loading scratch tests, constant load scratch tests, multiple scratch tests in the same track and indentation tests were all performed. It was shown that the modified scratch tester can be used to identify not only coating detachment during progressive load scratch tests, but also other failure events such as cracking and cohesive damage to the coatings. By using the additional modes of operation, it was possible to study the fracture mechanisms in more detail i.e. chipping in the scratch track was cohesive for the TiN coated steel and adhesive for the TiN coated Ti alloy. [Copyright &y& Elsevier]

Abstract: The grain size of as-cast Ti–6Al–4V is reduced by about an order of magnitude from 1700 to 200μm with an addition of 0.1wt.% boron. A much weaker dependence of reduction in grain size is obtained for boron additions from >0.1% to 1.0%. Similar trends were observed in boron-modified as-cast Ti–6Al–2Sn–4Zr–2Mo–0.1Si. [Copyright &y& Elsevier]

Abstract: This paper analyses a possibility to decrease the temperature of the industrial forming of the VT6 alloy. Experimental laboratory studies of the mechanical properties of the material show that one can lower the temperature of industrial superplastic forming. A developed mathematical model is proposed and enables to calculate an optimum pressurization taking into account the structural state of the shell material and principles of the shell friction on the die surface. The calculated pressurization enables to obtain the optimum superplastic properties of the material in the maximum area of the deformed shell. The proposed model has been checked up experimentally. In laboratory conditions, the forming of special workpieces with calculated pressurization has been conducted. The experimental researches confirm the made theoretical forecasts about a capability of decreasing the forming temperature of SPF VT6 alloy components. The studies have been made with the support of the international company AIRBUS GIE and the firm KOMMEK Ltd. (Russia). [Copyright &y& Elsevier]

The solid-state direct diffusion bonding of a near α-phase titanium alloy to an austenitic stainless steel by means of the phase transformation superplasticity (PTSP) caused by the cycles of heating and cooling has been carried out. The test results showed that, under the conditions of T max = 890°C, T min = 800°C, cyclic number of heating and cooling N = 10 cycles, specific pressure P = 5 MPa, heating rate V h = 30°C/s and cooling rate V c = 10°C/s, the ultimate tensile strength of the joint reached its maximum value (307 MPa), and the bonding time was only 120 s. In the phase transformation superplastic state, the deformation of titanium alloy has a character of ratcheting effect and it accumulates with the cycles of heating and cooling. The observations of tensile fracture interface showed that both the brittle intermetallic compound (FeTi) and the solid solution based on β-Ti were formed on the interface, and the more in quantity and the smaller in size the solid solutions are, the higher the ultimate tensile strength is. [ABSTRACT FROM AUTHOR]

Abstract: The effect of carbon and heat treatment on microstructural stability of a near-α titanium alloy Ti–5.6Al–4.8Sn–2Zr–1Mo–0.35Si–0.7Nd during high-temperature exposure was investigated. Aging leads to the precipitation of α2 phase from α after both β- and (α+β)-solution treatment. The α2 precipitates are uniformly distributed throughout the α matrix for alloys aged at 700°C and 750°C, but the precipitation is heterogeneous, preferring dislocations or other substructures during aging at 800°C. Carbon has little effect on α2 precipitation for fully lamellar microstructure because there is no partitioning of alloying elements. For bimodal microstructure with ∼15% primary α (αp), however, increasing carbon addition reduces α2 particle size and increases interparticle spacing in αp after exposure at 700–800°C for 168h, reducing and delaying α2-related embrittlement. This effect is attributed to carbon decreasing the Al concentration of the αp and increasing the partitioning of Al and Mo to the transformed β. [Copyright &y& Elsevier]

The “abc” deformation method for production of large-scale billets with submicrocrystalline structure was developed. A large billet of Ti–6Al–4V alloy (150-mm diameter×200-mm length) with a homogeneous submicrocrystalline structure was produced. The refined structure with a grain/subgrain size of about 0.4μm leads to a substantial mechanical properties improvement. [Copyright &y& Elsevier]

Presents information on a study which discussed the cobalt silicon formation processes and the choice for the cobalt/titanium process. Overview of the cobalt silicon formation processes; Description of the titanium and titanium nitrate layer; Conclusions.

Analyzes the use of refracted x-ray fluorescence in determining depth profile of a cobalt/titanium (Co/Ti) bilayer on silicon(100) before and after annealing. Formation of cobalt silicide following annealing; Presence of Ti during silicidation reaction; Observation of the intensity of cobalt radiation.

Presents an abstract of the article `Formation and Cleavage of the Cobalt-carbon Bond of Co-(Salen) Complexes with a Cobalt-to-ligand Carbon Bridge,' by R. Blaauw, J.L. van der Baan, et al from the `4th European Symposium on Vitamin B12 and B12-Proteins' dated September 2-6, 1996.