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The poor high‐temperature oxidation properties of Ti‐6Al‐4 V (titanium‐aluminum‐vanadium) alloy limit its applications under high‐temperature components of aero‐engines. In this study, the aluminum‐silicon coatings with different silicon content were fabricated on titanium‐aluminum‐vanadium alloy via the hot dipping route. A metallurgical bond was established at the interface between aluminum‐silicon coatings and substrates following the hot dipping. The results showed that three different coatings were formed: titanium(aluminum, silicon)3+ liquid‐(aluminum, silicon), titanium(aluminum, silicon)3+ τ2+ liquid‐(aluminum, silicon) and τ1+ τ2+ liquid‐(aluminum, silicon). Furthermore, the formation of aluminum‐silicon coatings was analyzed by diffusion path theory. The coated alloy was subjected to a high‐temperature oxidation test at 850 °C, and the weight gains were only 5.1 % to 22.4 % of the bare alloy. The coatings improved the high‐temperature oxidation resistance of titanium‐aluminum‐vanadium alloy. The most favorable oxidation behavior was noticed for the titanium(aluminum, silicon)3+liquid‐(aluminum, silicon) coatings. The higher the silicon content in titanium(aluminum, silicon)3+liquid‐(aluminum, silicon) coatings, the more excellent high‐temperature oxidation resistance was achieved. [ABSTRACT FROM AUTHOR]

One of the main problems that exists when working with Finite Element Methods (FEM) applied to machining processes is the lack of adequate experimental data for simulating the material properties. Moreover, for damage models based on fracture energy, the correct selection of the energy value is critical for the chip formation process. It is usually difficult to obtain the fracture energy values and requires complex tests. In this work, an analysis of the influence of this fracture energy on the cutting force and the chip generation process has been carried out for different sets of cutting parameters. The aim is to present an empirical relationship, that allows selecting the fracture energy based on the cutting force and cutting parameters. The work is based on a FEM model of an orthogonal turning process for Ti6Al4V alloy using Abaqus/Explicit and the fracture energy empirical relation. This work shows that it is necessary to adjust the fracture energy for each combination of cutting conditions, to be able to fit the experimental results. The cutting force and the chip geometry are analyzed, showing how the developed model adapts to the experimental results. It shows that as the cutting speed and the feed increase, the fracture energy value that best adapts to the model decreases. The evolution shows a more pronounced decrease related to the feed increment and high cutting speed. [ABSTRACT FROM AUTHOR]

Rapid absorption of impulses using light-weight, small, reusable systems is a challenging problem. An axially aligned set of progressively shrinking elastic spheres, a “tapered chain,” has been shown to be a versatile and scalable shock absorber in earlier simulational, theoretical, and experimental works by several authors. We have recently shown (see R. L. Doney and S. Sen, Phys. Rev. Lett. 97, 155502 (2006)) that the shock absorption ability of a tapered chain can be dramatically enhanced by placing small interstitial grains between the regular grains in the tapered chain systems. Here we focus on a detailed study of the problem introduced in the above mentioned letter, present extensive dynamical simulations using parameters for a titanium-aluminum-vanadium alloy Ti6Al4V, derive attendant hard-sphere analyses based formulae to describe energy dispersion, and finally discuss some preliminary experimental results using systems with chrome spheres and small Nitinol interstitial grains to present the underlying nonlinear dynamics of this so-called decorated tapered granular alignment. We are specifically interested in small systems, comprised of several grains. This is because in real applications, mass and volume occupied must inevitably be minimized. Our conclusion is that the decorated tapered chain offers enhanced energy dispersion by locking in much of the input energy in the grains of the tapered chain rather than in the small interstitial grains. Thus, the present study offers insights into how the shock absorption capabilities of these systems can be pushed even further by improving energy absorption capabilities of the larger grains in the tapered chains. We envision that these scalable, decorated tapered chains may be used as shock absorbing components in body armor, armored vehicles, building applications and in perhaps even in applications in rehabilitation science. [ABSTRACT FROM AUTHOR]

The effect of 3d transition elements (such as V, Cr, Mn, Fe, Co, and Ni additions) on material properties in L10 TiAl has been studied using the first-principles DMol and discrete variational method within the framework of the density-functional theory. The transfer energy calculation indicates that all these 3d elements show a tendency to substitute for Al sites in the stoichiometric TiAl alloy, with the increasing order V

In situ spatially resolved x-ray diffraction (SRXRD) experiments were used to directly observe the heat-affected zone phases present during gas tungsten arc welding of a Ti-6Al-4V alloy. The experiments were performed at the Stanford Synchrotron Radiation Laboratory using a 250 µm diam x-ray beam to gather real-time experimental information about the α-Ti→β-Ti phase transition during weld heating. Six different welding conditions were investigated using SRXRD to experimentally determine the extent of the single phase β-Ti region surrounding the liquid weld pool. These data were compared to predicted locations of the β-Ti phase boundary determined by calculated weld thermal profiles and equilibrium thermodynamic relationships. The comparison shows differences between the experimentally measured and the calculated locations of the β-Ti boundary. The differences are attributed to kinetics of the α-Ti→[sub -]Ti phase transition, which requires superheating above the β-Ti transus temperature to take place during nonisothermal weld heating. Analysis of the results reveal that the transition to β-Ti requires an additional 3.96 s (± 0.29 s) of time and 169 °C (± 25.7 °C) of superheat above the β-Ti transus temperature to go to completion under an average weld heating rate of 42.7 °C/s. [ABSTRACT FROM AUTHOR]

Abstract Due to the high specific strength of titanium, materials on its base are contemplated as a viable alternative in low-weight armor production. However, when the armor parts are fabricated using traditional and costly ingot and wrought technology, the feasibility of implementation is questionable. Proposed cost-efficient process of fabrication uses blended elemental powder metallurgy (BEPM). Multi-layered structures based on Ti-6Al-4 V alloy and its metal-matrix composites (MMC) with 5–10% (vol.) of TiC and TiB were fabricated and tested. Relatively large multi-layered plates and bars with TiC composite were successfully sintered due to very close shrinkage values of the alloy and composite. Shrinkage values of TiB composites were substantially lower than those for alloy, what led to delamination of layered structures, cracking and distortion of the plates. The difference in shrinkage behavior between the ML plates with TiC vs. TiB MMCs was explained by the difference in the ways those two types of reinforcement particles evolve within the structures. We have shown that by the optimization of the powder size and hydrogen content in BEPM process the shrinkage mismatch of the layered structures could be effectively nullified. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The effect of brazing parameters on the interfacial microstructure and mechanical properties of Ti6Al4V titanium alloy/316 L stainless steel brazed joint was investigated. The joint presented sectionalized interfacial microstructure by forming four reaction zones. The diffusion of Cu and Fe into Ti6Al4V titanium alloy substrate caused β-Ti transformation and its dissolution. Raising the brazing temperature promoted the dissolved blocky β-Ti to migrate to 316 L stainless steel side. Compared to the brazing temperature, the brazing time had relatively less impact on the microstructure of joint. The diffusion of Ti into steel substrate led to the formation of the transition zone which contained three different reaction layers-Fe 2 Ti, τ + α-(Fe, Cr), and γ-(Fe, Ni) + σ. With the increase of brazing temperature, the transition zone gradually thickened. The optimized joint shear strength was 65 MPa obtained at 960 °C/5 min. Contraction difference between two base metals generated stress concentration at Ti-Cu-Fe/Fe 2 Ti interface, which was a liquid/solid interface upon solidification. During shear test, cracks initiated at the Ti-Cu-Fe/Fe 2 Ti interface, and then mainly propagated within the reaction layers of Fe 2 Ti and τ + α-(Fe, Cr). [ABSTRACT FROM AUTHOR]

Abstract In the paper, the effects of porosities and average particle sizes of powder layer on light absorption during SLM process were investigated, in which closed-packing models based on Horsfieled's filling method were established and light absorption was simulated using ray tracing based on laser-material interaction mechanism. Corresponding to closed-packing models, the powder materials were prepared for absorption measurement using integrating sphere. The experimental results of light absorption verify the feasibility of the establishment of closed-packing models, the accuracy in calculation in the light absorption. The results show the absorption of powder layer of Ti6Al4V alloy is higher than 70%. The decrease of porosity of powder layer benefits to improve the absorption, while the absorption tends to decrease if porosity decreases to a certain value due to the reflection. The decrease of average particle size of powder particles benefits also to improve the absorption. If the light irradiates at positions with different particle arrangements, the absorption behavior changes with irradiation condition whether there occurs the multi-reflection. The above research provides theoretical basis for preparation of new powder materials, their parameter developing for SLM technology and even the properties regulation of SLM fabricated component. [ABSTRACT FROM AUTHOR]

Abstract The quest to achieve uniform dispersion of multiwalled carbon nanotubes (MWCNT) in metal matrices without compromising the structural integrity of the nanotubes during the production of metal matrix composites have been a lingering challenge across materials science community. The problem has compelled researchers to explore various techniques of dispersing MWCNT in metal matrices. In this study, 1.0 wt% MWCNT was dispersed in Ti6Al4V powders using shift speed ball milling technique to achieve uniform dispersion, good interfacial bonding and minimal structural strain to the MWCNT after dispersion. Two batches of dispersion techniques were adopted to disperse the nanotubes in the Ti6Al4V matrix. Batch 1 (6 h of low-speed ball milling + 1 h high-speed ball milling) and Batch 2 (8 h of low-speed ball milling + 1 h high-speed ball milling). After dispersion, various advanced characterisation techniques such as high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy and X-Ray diffraction (XRD) were utilised to evaluate the dispersion characteristics, interfacial bonding and micro and nanostructural evolution of the MWCNT in Ti6Al4V powders. The results indicated that batch 2 sample showed the best dispersion characteristics of MWCNT, good interfacial bonding with minimal strain to the walls of the MWCNT in the Ti6Al4V powders and this is ascribed to the adequate impact energy exerted on the powders during prolong milling time of low-speed ball milling and the supplementary 1 h of high-speed ball milling. Graphical abstract Image 1 Highlights • Shift speed ball milling is a novel method for effective dispersion of MWCNT in MMC. • Uniform dispersion with minimal strain on MWCNT in Ti6Al4V powders was achieved. • High impact energy of milling balls aids the dispersion of MWCNT in Ti6Al4V powders. • Structural evolution of MWCNT was confirmed by SAED, HRTEM, FFT and Raman analysis. [ABSTRACT FROM AUTHOR]

Abstract The dislocation structures of B2 phase in Ti-42Al-6V-1Cr alloy deformed at room temperature (RT), 700 °C and 800 °C were investigated in detail. At RT and 700 °C, the 〈110〉 type dislocations were active in B2 grains. The {111}〈110〉 slip systems satisfy the von Mises criterion and this is a contributor to the ductility. At 800 °C, three different types of dislocations were observed, containing 〈111>, <110〉 and 〈100〉-type dislocations. Based on microstructural evidence, recovery process occurs by a combination of rearrangement of dislocations and subgrain structures. The more slip modes are activated and this would lead to softening. Highlights • Deformation structures of B2 phase in Ti-42Al-6V-1Cr alloy were studied in detail. • The slip system is {111} 〈110〉 when B2 phase deformed at RT and 700 °C. • More slip modes are activated at 800 °C and this would lead to softening. [ABSTRACT FROM AUTHOR]

Highlights • In this study, Ti-Ni/TiN/TiS composite coatings on Ti6Al4V were fabricated by laser cladding. • The microstructures of Ti-Ni/TiN/TiS coatings were composed of dendrites, acicular phases and particles. • The coating (50%NiCrBSi-20%TiN-30%WS 2) with 842 HV 0.2 microhardness has excellent wear resistance property. • The Ti-Ni intermetallic, TiN and TiS play a critical role for reducing friction coefficient to 0.36. Abstract TiN reinforced Ni matrix composite coating with in-situ synthesized TiS lubricant phase were fabricated on Ti-6Al-4V alloy by laser cladding with NiCrBSi, TiN and WS 2 powder mixtures. The phase compositions, microstructure, microhardness and tribological behaviors are investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) as well as a multi-functional Tribometer. Effect of WS 2 contents on the microstructure, microhardness and tribological properties were studied. And the corresponding wear mechanism was discussed. Results indicate that the hardness of the coating (about 900HV 0.2) is significantly improved compared with substrate (370HV 0.2). Coefficients of friction and wear rates of these coatings have been significantly reduced. Besides, laser-clad coating using the mixed powders of 50%Ni-30%TiN-20%WS 2 has good anti-wearing and friction reducing effects, and the main wear mechanisms of that are abrasive wear and micro-plowing. [ABSTRACT FROM AUTHOR]

Abstract In-situ synthesized titanium borides reinforced Ti-6Al-4V composites with a tailored reinforcement architecture were successfully prepared by hot isostatic pressing (HIP) starting from a TiB 2 /Ti-6Al-4V powder system. The microstructure of the composite samples was investigated using X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), and the mechanical properties were evaluated through room and high temperature tensile testing. It is found that during HIP the additive particles TiB 2 have totally transformed into TiB needles, which tend to decorate at prior particle boundaries of the consolidated powder particles to form a network structure. With increasing TiB 2 addition from 3 wt.% to 8 wt.%, the microstructural feature of the TiB network structure experiences the variations of discontinuous TiB reinforcement → quasi-continuous TiB reinforcement → continuous TiB reinforcement. The room temperature tensile properties of the composites are improved with increasing addition of TiB 2 from 3 wt.% to 5 wt.%, but the tensile strength of the sample with 8 wt.% TiB 2 drastically decreases. As to the high temperature properties, the titanium boride reinforced Ti-6Al-4V alloy composites can be an increased maximum service temperature by over 200 °C while retaining the same tensile strength accompanied with a suitable elongation. The strengthening mechanism is mainly attributed to the load-bearing transformation, grain refinement and dispersion strengthening. [ABSTRACT FROM AUTHOR]

Abstract Additive manufacturing (3D printing) is emerging as a key manufacturing technique in medical devices. Selective laser melted (SLM) Ti-6Al-4V implants with interconnected porosity have become widespread in orthopedic applications where porous structures encourage bony ingrowth and the stiffness of the implant can be tuned to reduce stress shielding. The SLM technique allows high resolution control over design, including the ability to introduce porosity with spatial variations in pore size, shape, and connectivity. This study investigates the effect of construct design and surface treatment on tensile fatigue behavior of 3D printed Ti-6Al-4V. Samples were designed as solid, solid with an additional surface porous layer, or fully porous, while surface treatments included commercially available rotopolishing and SILC cleaning. All groups were evaluated for surface roughness and tested in tension to failure under monotonic and cyclic loading profiles. Surface treatments were shown to reduce surface roughness for all sample geometries. However, only fatigue behavior of solid samples was improved for treated as compared to non-treated surfaces Irrespective of surface treatment and resulting surface roughness, the fatigue strength of 3D printed samples containing bulk or surface porosity was approximately 10% of the ultimate tensile strength of identical 3D printed porous material. This study highlights the relative effect of surface treatment in solid and porous printed samples and the inherent decrease in fatigue properties of 3D printed porous samples designed for osseointegration. [ABSTRACT FROM AUTHOR]

Abstract Load-bearing implants success is strongly dependent on several physical and chemical properties that are known to drive cellular response. In this work, multi-material β-TCP-Ti6Al4V cellular structures were designed to combine Ti6Al4V mechanical properties and β-Tricalcium Phosphate bioactivity, in order to promote bone ingrowth as the bioactive material is being absorbed and replaced by newly formed bone. In this sense, the produced structures were characterized regarding roughness, wettability, β-TCP quantity and quality inside the structures after fabrication and the pH measured during cell culture (as consequence of β-TCP dissolution) and those aspects were correlated with cellular viability, distribution, morphology and proliferation. These structures displayed a hydrophilic behavior and results showed that the addition of β-TCP to these cellular structures led to an alkalization of the medium, aspect that significantly influences the cellular response. Higher impregnation ratios were found more adequate for lowering the media pH and toxicity, and thus enhance cell adhesion and proliferation. Highlights • β-TCP-Ti6Al4V cellular structures were designed and manufactured by combining AM technique (SLM) with Press and Sintering. • This structure design will allow bone ingrowth while the bioactive material is being absorbed and replaced by new bone. • Structures physical and chemical aspects were assessed and correlated with cell viability, adhesion and proliferation. • β-TCP amount inside these cellular structures has a significant impact on medium pH and thus on the cellular response. [ABSTRACT FROM AUTHOR]

Highlights • The evolution of the melt pool under a moving laser has been studied numerically. • The Marangoni force enhances the wetting phenomenon to the lateral powder. • The surface tension force causes the sloshing and periodic motion of the melt pool. • This study provides the morphology of the melt pool from a microscopic viewpoint. Abstract The complex evolution of a melt pool of Ti-6Al-4V powder particles under a moving selective laser was studied numerically. A laser power of 175 W and scanning speeds of 850, 1250, and 1650 mm/s were used. An effective laser source term with a time-varying maximum intensity was applied to a representative cross section to simplify the three-dimensional problem into a two-dimensional computational domain. The numerical results were validated using experimental observations. The effects of surface tension, Marangoni, and recoil forces on the interfacial morphology were investigated numerically. For a scanning speed of 1250 mm/s, the Marangoni effect initially begins to pull the interfacial melting flow from the laser focus region to the lateral powder. Meanwhile, the accumulated laser energy leads to evaporation, producing a corresponding recoil force. The transport phenomena caused by the Marangoni effect and the inward recoil force contribute to the local suppression of the melt pool. The Marangoni flow conveys the laser energy to the lateral powder, which significantly enhances the wetting phenomenon. In the next stage, the surface tension force gradually becomes dominant, eliminating the local suppression and concave curvature. The interfacial curvatures in this stage overshoot when they change signs. This tendency results in a periodic sloshing motion and oscillation of the melt pool. This study provides a thorough understanding of the wetting and morphology of the melt pool from a microscopic viewpoint, which could result in detailed design guidelines. [ABSTRACT FROM AUTHOR]

Abstract In the study, an innovative carbonitriding process was implemented to increase hardness and hardening depth of Ti-6Al-4V alloy via laser irradiation of pure graphite powder in a nitrogen environment. The formation of the carbonitrided layer on the surface depends on the diffusion of carbon and nitrogen atoms and the kinetics of carbonitriding reaction. Dendritic phase transformations within the hardened layer help in determining the overall depth and hardness of the hardened layer. To characterize the proposed carbonitriding process more fundamentally, samples of an Ti-6Al-4V alloy were self-quenched (SQ), laser-carburized (LC), laser-nitrided (LN), and laser‑carbonitrided (LCN) at the same laser irradiation conditions. This was followed by comparing the microstructural evolutions and mechanical properties of the respective samples after laser surface treatments. The hardening characteristics of the respective laser surface treatments were significantly influenced by the reaction compounds and laser energy density. The LCN Ti-6Al-4V alloy was dominated by compounds with mixed structure of carbonitrides and exhibited excellent hardness with increase in hardening depth. The results confirmed that the proposed laser carbonitriding is a feasible and effective process to increase the hardness and hardening depth of Ti-6Al-4V alloy without process-induced cracks. Highlights • Carbonitriding of Ti6Al4V via laser irradiation of graphite powder in N 2 environment • Tailored hardening by controlling the reaction compounds and laser energy density • Enhanced hardening efficiency in laser carbonitriding with pure graphite powder [ABSTRACT FROM AUTHOR]

Abstract Two layers of Ti-36Nb-2Ta-3Zr-0.3O (wt%, gum metal) were deposited on the Ti6Al4V substrate by direct laser deposition. The microstructures, mechanical properties and corrosion resistance of the cladding layer were investigated. The results show that the single β phase columnar with different orientation was obtained in the second cladding layer, and a large amount of α″ martensites exist in the first cladding layer. The absence of the toxic elements of Al and V in the second cladding layer indicates gum metal coating can promote the long-time performance of Ti6Al4V. Nanoindentation tests show that the elastic modulus is about 75GPa at the surface of gum metal coating, decreased by about 40% compared with the Ti6Al4V substrate. The corrosion resistance of Ti6Al4V is improved by the formation of β phase on the coating. Ti6Al4V coated with gum metal by direct laser deposition can be regarded as a potential candidate to integrate the advantages of the two Ti-base alloys for application in the biomedical field. Highlights • Two layers TNTZO alloy were deposited on Ti6Al4V by direct laser deposition. • The toxic elements of Al and V in Ti6Al4V are absent in outermost layer. • The corrosion resistance of Ti6Al4V is improved in 3.5 wt% NaCl solution. [ABSTRACT FROM AUTHOR]

Abstract In machining of hard metals, surface roughness, tool vibration and tool wear are used as performance characteristics to estimate overall performance of process. This work is aimed to maximize overall performance in micromachining of Ti-6Al-4V and investigate effect of process parameters on performance characteristics. As per orthogonal array of L27, twenty seven experiments are carried out on the proposed metal with cemented carbide tools at three levels of cutting speed, feed and depth of cuts. According to user's preference rating, graph theory and matrix approach is used to estimate weights and preference scales for the performance characteristics. Utility concept is used to calculate overall performance of the process using weights and preference scales. Responses surface methodology is used to optimize process parameters to maximize overall performance of the process. In this study, maximum performance of the process is found at cutting speed of 19.78 m/min, feed of 75 μm/tooth and depth of cut of 50 μm. In addition to that, metal recovery in machining due to elastic recovery is also estimated theoretically and measured practically for different uncut chip thicknesses. Highlights • Effect of process parameters on individual performance characteristics and overall performance of the process was studied. • Weights for the performance characteristics were estimated according to user's preference rating. • Utility concept was used to calculate overall performance of the process. • Process parameters were optimized to maximize overall performance of the milling. • Metal recovery in machining due to elastic recovery was calculated and measured. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Volumetric heat source has been used in modeling of SLM of Ti6Al4V. • Simulation of moving single scan and multi-scan. • Porosity is estimated and compared with the experiment. • Porosity forms due to improper melting in the powder bed. • The solidification parameters are calculated to estimate solidified grain structure. Abstract A volumetric heat source is used in numerical modeling of selective laser melting (SLM) of Ti6Al4V powder. Single track and multi-track SLM simulations are performed by varying the two key process parameters-laser power and scan speed. The model is validated with the published experimental results for melt pool shape, size and temperature. The predictions are in good agreement with the experiments at low to medium energy density. The validated model is used for investigating the thermo-fluidic transport during SLM of Ti6Al4V and examining the dependence of the melt pool characteristics on the process parameters. As-solidified porosity is calculated numerically for the multi-track simulations and its formation is delineated with the transport phenomena. The predicted porosity compares reasonably well with the experimental values. Solidification parameters, such as temperature gradients and cooling rate are calculated at the instantaneous location of the solidification front and analyzed. This analysis suggests the formation of fully columnar grains of different sizes along the width and depth of the melt pool. Overall, the model provides a good description of thermo-fluidic transport in SLM of Ti6Al4V powder and the resulting temperature field, melt pool characteristics, as-solidified porosity and the expected grain structure. Based on the current analysis, an optimum processing window of 50–70 J mm−3 energy density is suggested for SLM of Ti6Al4V powder. [ABSTRACT FROM AUTHOR]

Highlights • SLM-fabricated Ti-6Al-4V alloy was characterised in detail using μ-XRD. • Distinct changes in constituent phases occurred in SLM-fabricated Ti-6Al-4V. • Lattice parameter contour maps were produced for α, α′ and β across entire specimen section. • α′-martensite showed much lower elastic modulus than α-β in Ti-6Al-4V. • μ-XRD 2D patterns provide an improved approach to identifying the β-phase in Ti-6Al-4V. Abstract Additively manufactured Ti-6Al-4V implants represent a premier application of metal additive manufacturing (AM) since 2007. Microstructural inhomogeneity can noticeably affect one or more aspects of their mechanical or biomedical performance. This paper investigates the microstructural inhomogeneity in selective laser melting (SLM)-fabricated Ti-6Al-4V using micro X-ray diffraction (μ-XRD) and the consequent changes in elastic modulus (concerns are trivial with other mechanical properties of SLM Ti-6Al-4V implants). Cylindrical specimens of ϕ12 mm × 20 mm (few Ti-6Al-4V implants are thicker than 20 mm) were manufactured by SLM for detailed charaterization. μ-XRD (beam size: 500 μm) was applied to 40 uniformly spaced regions at different build heights, assisted with microscopic examination. The distribution of lattice parameters for each phase was mapped out based on a detailed analysis of the μ-XRD two-dimensional (2D) diffraction data (ring patterns). The bottom half of the cylindrical specimen consisted of essentially α and β while α′-martensite was prominent above the mid-height, with the top 3.5-mm thick region being fully martensitic. In relation to this, the elastic modulus was found to decrease almost linearly from the mid-build height to the top. It is further shown that the μ-XRD 2D ring patterns offered an improved approach to characterising the β-phase in SLM Ti-6Al-4V. The implications of these findings are discussed explicitly. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Ti6Al4V is one of the most widely used ternary alloys in additive manufacturing. Its mechanical properties are highly determined by the prior β phase. However, simulation of the ternary alloy solidified microstructure is limited for the lack of available methods. In this study, we carried out two-dimensional (2D) and three-dimensional (3D) simulations based on a new multi-component (MC) phase-field (PF) model by extending Karma's binary PF theory. The correctness and accuracy of the MC model are validated by the Gibbs-Thomson relation at dendrite tip. With the equipment multiple GPUs, the highest speedup ratio more than 150 is obtained compared with serial programming running on one of the top CPUs and simulations with billion nodes can be completed within acceptable time. Using this model as benchmark, previous Ti6Al4V dendrite evolution using pseudo-binary PF model is investigated and found magnifying the driving force and growth artificially. 3D large-scale directional solidification simulations also shed light on dendrite merging which leads coarse primary dendrites. We believe that the GPU-accelerated MC PF framework provides an accurate and efficient insight in understanding the solidifying evolution for Ti6Al4V. [ABSTRACT FROM AUTHOR]

Abstract Brazing C/SiC composites to Ti6Al4V alloy is associated with the problem of high residual stress inducing low joining strength. To overcome this problem, negative thermal expansion Zr 2 P 2 WO 12 (ZWP) nanoparticles were introduced into AgCu brazing alloy to obtain robust C/SiC-Ti6Al4V joints. Microstructures and mechanical properties of the joints brazed with different ZWP contents were investigated. Results indicated that 3 wt% ZWP nanoparticles dispersed homogeneously among brazing seam and compatible with brazing alloy. The width of reaction layer at C/SiC side was reduced sharply. Meanwhile, the finite element analysis showed that residual stress was reduced by 52.9 MPa and stress concentration among reaction layer was eliminated. The average shear strength of the joints brazed with AgCu + 3 wt% ZWP increased to 146.2 MPa, which was 70.8% higher than that of joints brazed without ZWP. [ABSTRACT FROM AUTHOR]

Abstract In the present work, CrMnFeCoMoW high entropy alloy powder and Al- CrMnFeCoMoW composite coatings were successfully synthesized on Ti-6Al-4V alloy substrate via mechanical alloying method. The final milling products for as-milled CrMnFeCoMoW high entropy alloy powder consist of body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases. The composite coatings exhibit a composite structure consisting of white high entropy alloy particles and Al-rich gray regions. The adhesion of the coating was tested by scratch experiment. The effects of the ratio of Al-CrMnFeCoMoW powder ratio and milling time on the preparation of composite coatings were investigated. The microstructure and element distribution and phase composition of the coating had been studied. The results show that under the optimal parameters, the thickness of the coating is 180 μm, which shows a good bonding with the Ti-6Al-4V alloy substrate. The high temperature cyclic oxidation test was carried out at 850 °C. The oxidation resistance of the coating was compared with that of the traditional oxidation resistant coating. The composite coating obviously exhibits better oxidation resistance than traditional coating. Highlights • A composite coating on high entropy alloy was prepared by mechanical alloying. • The coating is a composite structure composed of white particles and gray areas. • Effects of Al-CrMnFeCoMoW powders ratio and milling time on the fabrication of composite coating were investigated. • The oxidation resistance of the coating was tested and the mechanism of oxidation resistance was analyzed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The vacuum processed µ-patterns exhibited ultrahydrophobic (CA: 180°) surface. • The vacuum processing duration is directly proportional to wetting condition from hydrophobic to ultra-hydrophobic. • The dual geometry structure is extremely water repellent. • The water bounces and rolls off from laser patterned surface to virgin surface. Abstract A novel technique of post-vacuum processing the laser patterned surface was used for high speed fabrication of Ultrahydrophobic Ti6Al4V surface and the basics behind the transformation of surface chemistry is investigated in this paper. The wetting property of the laser patterned dual geometry structures transforms to ultrahydrophobic in 120 min of vacuum process without any chemical treatments to suppress the surface polarity. The surface recorded static contact angle of 180°, sliding angle less than 5, and exhibits bouncing and roll-off characteristic due to the presence of composite interface. The transformation of hydrophobic property establish a clear relationship between the vacuum process period and the improvement in static contact angle. The surface chemical analyses by XPS reveals that the amount of surface carbon content increases 2.3 times higher because of the adsorption of unstable organic molecules by vacuum process. The low partial pressure of the water molecules (120 min.) compared to those occurs at standard atmospheric pressure (days). The transformation of freshly laser processed Ti6Al4V hydrophilic surfaces into ultrahydrophobic surface is due to the development of carbonaceous layer over the laser patterned structures, which helps to sustain the Cassi-Baxter state. [ABSTRACT FROM AUTHOR]

Abstract Laser melting deposition (LMD) technology enables the use of complex titanium alloy parts in ballistic applications such as lattice armors and warheads. The effect of the α phase of a LMD Ti-6.5Al-1Mo-1V-2Zr titanium alloy during compression at a high strain rate of 3000 s⁻1 was investigated. Various morphologies and textures of the α phase of the LMD alloy were obtained by annealing at different temperatures at the β transus, followed by furnace cooling. It was found that all the α phases of the annealed microstructures exhibit two fiber textures, <21̄1̄0>α and <16 0 16 ¯ 19>α, parallel to the building direction. The reason is that the <100>β directions of the prior-β grains were parallel to the building direction. Due to a high Schmidt factor, {101̄2} twinning occurs in the α phases with the <21̄1̄0>α fiber texture during the high-strain rate deformation. After annealing at 970 °C, the volume fraction of the α phases with the <21̄1̄0>α fiber texture increases significantly to 51.4 vol%, which leads to a significant improvement of 14.3% in the uniform ductility strain. Moreover, with an increase in the annealing temperature from 930 °C to 970 °C, the flow strength of the sample decreases slightly by 2%. [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 Local mechanical properties of Ti-6Al-4V butt joints produced by friction stir welding (FSW) were investigated using the shear punch testing and correlated with the global mechanical properties, microstructure, and microtexture evolution of the joint. The conditions for obtaining defect-free joints, under high heat input conditions were determined for the investigated alloy. The shear punch results revealed important differences in yield and ultimate strength between the base material (BM), the heat affected zone close to the BM (HAZ1), the heat affected zone close to the nugget (HAZ2) and two distinct regions in the stirred zone (SZ1 and SZ2). Electron microscopy examination indicated that the microstructure of the BM was converted from equiaxed and elongated α grains with an average size of about 20 µm and a basal transverse texture to a very fine, less than 1 µm diameter, equiaxed microstructure at the center of the SZ, while bimodal structures with lamellar and equiaxed grains were found elsewhere. The analysis of the local mechanical properties indicated that HAZ1 had the lowest mechanical properties of the joint and the obtained results are interpreted in terms of transition texture evolution from the BM to the HAZ using misorientation analysis of high resolution EBSD maps. [ABSTRACT FROM AUTHOR]

An approach of sintering 3D metal printed lattices and diamond nickel-coated particles is proposed which can be used for the production of tunnel boring machine (TBM) cutters and mining equipment blades. Nickel-coated diamond particles are mixed with titanium powder and incorporated into a lightweight Ti6Al4V (3D printed) lattice with the help of spark plasma sintering (SPS) method. Effect of Ti6Al4V lattices size, diamond particles size, and nickel coating layer thickness on wear resistance of composites is discussed. Functionally graded lattice (FGL) structures were produced by selective laser melting (SLM) method, representing an increasingly growing additive manufacturing engineering area introduced in material engineering. Impact-abrasive tribo-device (IATD), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and optical surface profiler (OSP) were used to characterize samples. An ab initio design of diamond-metal composite is based on the improvement of impact and abrasive wear resistance of Ti6Al4V by adding diamond particles and by applying of gradient lattice structure. The specimen with larger size of the diamond particle and thicker Ni coating has better wear resistance. In addition, ANSYS software simulations were done to analyze the effect of the presence of 3D printed lattice via nonlinear finite element AUTODYN solver under impact test. Diamond-based gradient composite material produced by combined SLM-SPS methods can be applied in applications where resistance against impact-abrasive wear is important. [ABSTRACT FROM AUTHOR]