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In this study, a combined experimental and simulation method was proposed to determine the friction coefficient involved in wire drawing processes. Subsequently, the hot drawing experiments and finite element analysis (FEA) of Ti–6Al–4V alloy wire were conducted. The influence of drawing parameters, such as drawing temperature (650 °C, 700 °C, 750 °C), speed (1 m/min, 3 m/min, 5 m/min) and deformation (12.9%, 13.7%, 14.8%) on temperature rise, equivalent plastic strain and residual stress were predicted. The temperature rise exhibits a notable decline with the elevation of the initial temperature, the acceleration of the drawing speed, or the reduction of the deformation amount. Additionally, the equivalent plastic strain increases with increasing initial temperature, speed and deformation. The residual compressive stress in the core decreases from −476 MPa to −279 MPa as the initial temperature increases, increases from −312 MPa to −403 MPa with the acceleration of drawing speed, and decreases from −357 MPa to −290 MPa with the reduction of deformation. Furthermore, the experimental results demonstrated that as the initial temperature increased and the drawing speed increased, the tensile strength decreased by 5.09% and 5.31%, respectively. In contrast, as deformation increased, the tensile strength increased by 5.13%. Meanwhile, the relationship between drawing force and tensile strength was corrected. The obtained equation can accurately predict the drawing force of Ti–6Al–4V alloy.

In this study, we present a microstructural and mechanical analysis of Ti–6Al–4V alloys processed by low-temperature multi-directional forging at 900 °C, achieving near-theoretical density (99.9%), with a tensile strength of 1070 MPa and elongation of 14.9%. The microstructure is defined by both continuous and discontinuous dynamic recrystallization occurring simultaneously, related to an increase in dislocation density. Significantly, this study reveals the interaction between crystallographic orientation and spheroidization during the forging process. Specifically, changes in crystallographic orientation include the asynchronous formation of new subgrains/grains, the disruption of the Burgers orientation relationship, and rotation around the axis, which not only increases the orientation differences between α lamellae but also enhances the spheroidization process. Moreover, our findings demonstrate that during deformation, the activation of basal and pyramidal slip systems is favored over prismatic slip, indicating that the forging process has enhanced slip activity. The average misorientation angle and the fraction of high-angle grain boundaries are quantified, providing a detailed characterization of the evolved microstructure. This study adopts a new perspective to examine the microstructural evolution during the multidirectional forging process in powder metallurgy, presenting findings that elucidate how multidirectional forging effectively controls.

Fatigue indicator parameters (FIPs) can serve as a measure of fatigue crack initiation (FCI) in metals and alloys. FIPs are volume averaged over grains, bands, and sub bands in crystal plasticity (CP) simulation to investigate the influence of texture on FCI under low cycle fatigue. The equiaxed microstructure of Ti–6Al–4V was generated with three different textures: basal, basal/transverse and transverse. FIPs analysis shows that basal texture has the highest FCI resistance, basal/transverse texture has intermediate resistance, and transverse texture has the lowest resistance when tested along plate direction. All textures exhibit a lower FIP when deformed along rolling direction (RD) than that along transverse direction (TD). The interior of the alloys has a larger FCI resistance than the free surface. Further analysis shows a strong relationship between FIP distribution features and damage nucleation characteristics, with basal texture exhibiting the lowest and wider FIP distributions as a result of high resistance to damage and fatigue cracking; in contrast, the transverse texture exhibits intense and narrow FIP and damage nucleation along the grain boundaries (GBs), basal/transverse texture exhibits FIP and damage nucleation with mixed characteristics. The results can be used as a theatrical reference for the fatigue performance design of Ti alloy.

Achieving excellent strength-ductility balance in commercial titanium alloys has been recognized as a challenging task. In this study, we designed a heterogeneous equiaxed structure in Ti-6Al-4V alloy via cryogenic pre-stretching at liquid nitrogen temperature. The results show that 7.1% cryogenic pre-stretching of the alloy induces an increased yield/tensile strength of 952 MPa/1005 MPa and maintains a high elongation of 16.1% compared with the as-received alloy (840 MPa/930 MPa and 16.3%, respectively). Compared with ambient deformation, cryogenic deformation can promote the basal slip system activation, dislocation accumulation, and α grain fragmentation. For the heterogeneous equiaxed structure, the grain boundaries between large equiaxed and small fragmented α grains act as barriers for dislocation motion and cause the significant strain gradient and back stress strengthening effect, thus leading to an enhanced strength. On the other hand, the lamellar α fragmentation release the large local stress concentration during cryogenic pre-stretching, which maintains the high work hardening capacity of the alloy. Besides, the parallel lamellar α grains with similar crystal orientation (i.e., macrozone) are destroyed after cryogenic pre-stretching, which is beneficial to hindering the crack propagation during deformation. This study provides an insight into further conquering the strength-ductility paradox of titanium alloys.

This study investigates the optimization of cutting conditions for machining titanium alloy (Ti-6Al-4V) using Response Surface Methodology (RSM), with the goal of minimizing tool-chip interface temperature and surface roughness. The research focuses on key cutting parameters to investigate the most effective combinations for enhancing surface finish and reducing thermal impact during machining. The present study deals with the dry turning of Ti-6Al-4V alloy with carbide alloy inserts in a way to utilize the Analysis of Variance (ANOVA) to develop predictive models for minimum surface roughness and optimum temperature. The findings reveal that both cutting speed and depth of cut are critical in determining machining outcomes. Specifically, a low cutting speed of 88 m/min coupled with a high depth of cut of 0.20 mm was found to elevate the cutting temperature to approximately 835 °C, resulting a surface roughness of 0.59 μm. Conversely, increasing the cutting speed to 120 m/min while reducing the depth of cut to 0.10 mm significantly lowered the temperature to around 607 °C, resulting a surface roughness of 0.19 μm; thus, thereby improving surface finish and reducing thermal stress on the tool. Additionally, a 27 % reduction in cutting temperature and a minimum surface roughness of 0.19 μm were achieved with optimal settings of 120 m/min cutting speed, 0.08 mm/rev feed rate, and 0.10 mm depth of cut. The study demonstrates the effectiveness of RSM in optimizing machining parameters for optimum temperature and better surface finish in the titanium alloy machining.

One of the biggest advantages in metal additive manufacturing using laser powder bed fusion is low powder usage compared to traditional manufacturing methods. The process can be made more efficient by enabling metal powder to be reused. Recycling promotes environmental sustainability by minimizing material wastage and decreasing the demand for raw materials, making the metal additive manufacturing process more resource efficient.In this study, Ti6Al4V powder was recycled and reused up to 50 times. In order to understand the effects of reusing powder, the study included a detailed examination of both the powder and the processing method. The microstructure and characteristics of the recycled powder were examined in extensive detail.

Texture is inevitably generated during the rolling process of titanium alloys, which has a significant impact on mechanical properties. The relationship between microstructure, texture and mechanical properties of the rolled Ti–6Al–4V alloy plate with large thickness was systematically investigated in this study. The texture type varied with the thickness of the plate. The basal pole concentrated in the transverse direction (TD) at the surface of the plate and tilted from TD towards the rolling direction (RD) at the quarter thickness of the plate. For the center of the plate, the basal pole had peaks concentrated close to both TD and RD. Tensile tests indicated that TD samples not only have high strength but also maintain good plasticity compared with RD and the normal direction (ND) samples. The yield anisotropy could be explained by the difficulty of prismatic and basal dislocation slip. The cold creep behavior of the thick plate depended on both Schmid factor of dislocation slip and grain size. Moreover, the strain hardening exponent was positively correlated with cold creep strain. Abundant prismatic and pyramidal dislocations were activated, and slip transfer and cross-slip made the dislocation slip distance longer, which contributed to creep strain and thus reduced the creep resistance of ND sample.

The ultra-precision Ti–6Al–4V alloy parts are growing used in medical and aerospace industries, and which always work in the extreme working conditions such as high temperature, high pressure, and variable load. Thus, the requirements for machining accuracy and surface quality of parts are getting higher and higher. The ultrasonic elliptical vibration assisted cutting (UEVC) technology has been proved to be an effective method for the ultra-precision machining of Ti–6Al–4V alloy. However, in the UEVC process, the evolution mechanism of microstructure and microhardness, which directly affect the service performance and life, is unrevealed. In this paper, the comprehensive investigations of microstructural plastic deformation, grain refinement, phase transformation and microhardness of machined surface layer under conventional cutting (CC) and UEVC processes are carried out. The experimental results indicated that, due to the effects of UEVC technology, the plastic deformation area show obvious compression deformation, the depth of plastic deformation is less than 10 μm, there is no obvious phase transformation on the machined surface layer material, and the hardening rate of machined surface is more than 20%. These findings show the UEVC technology has a unique influence on the microstructure and microhardness of Ti–6Al–4V alloy, which have important implications for the cutting parameter design of ultra-precision Ti–6Al–4V alloy parts.

The ultra-fine grain Ti–6Al–4V alloy sheet was successfully achieved by friction stir processing (FSP). The low-temperature superplastic deformation mechanism of Ti–6Al–4V alloy under the strain rate of 3 × 10−4 s−1 at 600 °C was studied by scanning electron microscope, electron backscatter diffraction and superplastic tensile test. It is found that the grain size of Ti–6Al–4V alloy by FSP is refined from 7.48 μm to 0.82 μm, and there is no preferential crystallographic orientation of the uniform grain. After FSP, the β phase of the base material (BM) in the grain boundary is refined and homogenized. During the superplastic tensile processing, with the increase of strain, the grain is refined continuously, and the α→β phase transition is induced by the dislocations pile-up at the β grain boundary, and the content of β phase increases. The grain near the fracture was refined to 0.35 μm, and the stress concentration led to the formation of cavities near the β phase, which eventually caused the fracture. The dynamic recrystallization in superplastic tensile processing is mainly geometric dynamic recrystallization and discontinuous dynamic recrystallization. The elongation of superplastic tensile (1033%) is 19.7 times higher than that of BM (50%). The order of superplastic deformation mechanism in the low-temperature superplastic deformation of the ultra-fine grain Ti–6Al–4V alloy sheet is as follows: intragranular dislocation slip and diffusion, grain boundary sliding, and phase boundary sliding. Phase boundary sliding is the main deformation mechanism for low-temperature superplastic deformation.

Powder metallurgy (PM) technology is expected to provide a promising strategy for the cost-effective and highly efficient utilization of spherical Ti–6Al–4V powders with particles size of large than 150 μm to reduce material waste. However, how to overcome the problem of low sinterability and poor ductility of coarse lamellar microstructures of large-diameter spherical powders are still remains a significant challenge. In this study, Ti–6Al–4V alloys were prepared by spark plasma sintering (SPS) at different sintering temperatures with plasma rotating electrode process (PREP) large-diameter spherical powders (∼156 μm). The microstructure evolution, grain structure, mechanical properties and fracture mechanisms were systematically investigated. Results demonstrate that the acicular martensite structure inside the unmelted particles changed to a uniform and fine α/β lamellar microstructure with the increased sintering temperature. Consequently, the Ti–6Al–4V alloys exhibit excellent strength-ductility at 925 °C. (ultimate tensile strength of 881 MPa and elongation up to 14.8 %). Fundamentally, the excellent strength-ductility was attributed to the uniform and dense fine α/β lamellar structure that enhanced the effective bearing area during deformation. The stacked dislocations at the α/β phase interface provided high strength. In addition, the high-density α/β phase interface in the matrix reduced the mean free path of the dislocation, which resulted in a high strain hardening rate of the high-density geometrically necessary dislocations (GNDs) and delayed the premature fracture. The intergranular brittle fracture mode of the alloys changed to the ductile fracture mode. These findings have important implications for recycling super-large diameter spherical powders.

The high-temperature wear resistance plays an important role for Ti–6Al–4V alloy components working in extreme environments, especially vital for avoiding unexpected failure. However, the reasonable method of surface modification should meet the requirement of improving in wear resistance and less decreasing in mechanical properties simultaneously, which brings a great challenge. In the present research, the laser shock peening (LSP) technique was applied to optimize the superficial layer of Ti–6Al–4V alloy by different processing. The microstructure, elastic modulus, nano-hardness and high-temperature tribology properties of the LSP processed Ti–6Al–4V were investigated to reveal the improving effect. The results demonstrate the LSP processing transforms the dual-size grain structure to relative homogeneous grain structure and forms the gradient nano-structure in superficial layer. With the increasing of LSP processing numbers, the density of geometrically necessary dislocation (GND) decreases obviously, but the density of statistically stored dislocation (SSD) rises significantly, which promotes the increase of total dislocation density compared with the as-received (AR) alloy. Due to the crystal evolution, the Ti–6Al–4V alloy with three-times LSP processing has the lowest wear rate which is less than half of the as-received state. The observations on worn surface and adjacent cross-sectional microstructure reveal the severe scratching and many inner microcracks in the AR sample but the slight scraping and few inner microcracks in the three-times LSP processed sample. Considering the elevated nano-hardness and elastic modulus, the improved tribological properties should be mainly attributed to the optimized microstructure and dislocation state by LSP processing. The present research provides a more reasonable method to improve the high-temperature wear properties of Ti–6Al–4V alloy.

Sub-atmospheric pressure environment and oscillation laser are both excellent ways to improve welded joint quality. However, the differences in their effects and mechanisms are unclear. Therefore, the differences between sub-atmospheric pressure and oscillating laser in weld formation, porosity suppression and grain size refinement were analyzed in this study. The results revealed that penetration depth of welded joint was increased to 6.09 mm under sub-atmospheric pressure environment while it was decreased to 3.3 mm under oscillation laser. Furthermore, reducing fluctuating vapor pressure and suppressing vortex formation were the main means to improve the keyhole stability and promote the escape of bubbles in a sub-atmospheric pressure environment. The improvement of the oscillating laser in these two aspects was attributed to enlarging keyhole area, shortening escape path and oscillation keyhole absorption. Additionally, the average grain size in the upper weld was reduced from 134.6 μm to 118.6 μm and 114.1 μm under the sub-atmospheric pressure environment and laser oscillation, respectively. The reduction of the temperature gradient led to former grain refinement while the increase of heterogeneous nucleation rate was responsible for latter grain refinement. Correspondingly, the mechanical properties of welded joints were improved. The study offered valuable insights for the application of laser welding with oscillation laser and sub-atmospheric pressure in industrial production.

In this study, active interpass cooling using various compressed CO2 gas strategies was applied to wire-arc additively manufactured Ti–6Al–4V alloy, and as-manufactured microstructure characteristics, including phase composition, grain growth and microhardness, were fully explored by using Electron Backscattered Diffraction and hardness tester. Results show that rapid interpass cooling brings obvious martensite phase transformation, primarily from lamellar α grains to acicular α grains, to the deposited component. The microstructure tends to be fine-grained, disordered and displays reduced texture strength and increased dislocation density through visible coloration. This feature also exhibits high hardness values that brings an improvement in mechanical strength to deposited metal. Moreover, it is found cooling time variation could obtain better grain refinement than altering cooling gas flow rate during deposit, which is probably related to effective heat dissipation. The research findings can provide significant insight into microstructural evolution mechanism in wire-arc directed energy deposition process, and benefits to properties control.

Additive manufactured titanium alloys are generally characterized by columnar grain structures along the vertical direction (VD), thereby causing a relative lower plasticity in the horizontal direction (HD) than that in the VD direction. However, herein we report that such columnar grain structures in the Ti–6Al–4V alloy produced by electron beam direct energy deposition (EB DED) can induce a superior uniform elongation in the HD direction than that in the other loading directions (22.5°,45°, 67.5° and VD directions). Besides the orientation of α laths with a favorable soft and hard match when the loading direction is along the HD, such anisotropic plasticity also can be attributed to the columnar grain structures which can also effectively prevent dislocation slip and suppress the necking of the HD sample, thereby triggering a greater work-hardening rate and strain hardening exponent in the stage of uniform deformation, and increasing the uniform elongation in the HD. The greater total elongation in the VD is mainly reflected in its higher non-uniform elongation, rather than uniform elongation, which is mainly caused by the α laths possessing easily activated basal slip system inducing strain softening. As for the 22.5° and 45° samples, most of the α laths under such loading directions present hard orientation, thereby leading to both lower non-uniform elongation and total elongation. The above information offers a deeper understanding about anisotropic plasticity in additive manufactured titanium alloys, thereby providing a theoretical basis for optimizing the consistency of mechanical properties.

The room temperature deformation behaviors of Ti–6Al–4V were investigated using crystal plasticity (CP) simulations to analyze the influence of texture on the mechanical and micromechanical properties of the alloy. The equiaxed microstructure with four different textures, namely random, basal, basal/transverse, and transverse, were generated using Dream 3D software. The alloy with random texture was used to study the influence of basal and prism critical resolved shear stress (CRSS) on the alloy properties. The findings revealed that the strength of the alloy is more sensitive to an increase in basal CRSS, whereas an increase in prism CRSS significantly affects plasticity. The analysis of microstructural stress and strain showed that the hard α grains accommodate the majority of the stress in the microstructure, while the soft α and β grains accommodate plastic strain. The simulations indicated that the basal texture exhibits the lowest strength and twin fractions, the basal/transverse texture displays intermediate strength, and the transverse texture has the highest strength along both the rolling direction (RD) and transverse direction (TD), accompanied by the highest twin fractions along TD. The alloy showed the highest strength when loaded along TD, parallel to the c-axes of the most frequently occurring grains, while the lowest strength was observed when loaded along RD, perpendicular to the c-axes of the most frequent grains. Under both tension and compression, the highest twin fractions were observed along TD, followed by RD, and then the through-thickness (TT). This research provides valuable insights into the mechanical and deformation mechanisms of titanium alloys under common textures.

Ti–6Al–4V alloy was pack carburized at temperatures of 950–1100 °C within a holding time range of 1–10 h. The structures and constituent phases of carburized layers were analyzed by optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD). The structure of carburized layer was strongly influenced by carburizing temperature, it mainly consisted of a transition zone sub-layer of α-Ti (C) solid solution at 950 °C, and a compound (Ti-carbides + Ti-intermetallics) sub-layer as well as a transition zone sub-layer at temperatures of 1000–1100 °C. The growth of compound sub-layer was controlled by the growth of Ti–Al intermetallics and chemical reaction between C and Ti–Al intermetallics, and the growth of compound sub-layer required a gestation period depending on carburizing temperature. The growth kinetics of compound sub-layers followed a parabolic law beyond gestation period, from which the diffusion activation energy was calculated to be 192.597 kJ/mol. Carburizing of Ti6Al–4V alloy leads to a reduction of over 96.16 % in wear rate, and the wear resistance is enhanced with increasing carburizing temperature.

The laser powder bed fusion manufactured Ti-6Al-4V alloy predominantly consists of α' martensite, resulting in excellent strength but limited ductility, hinders widespread application. Therefore, it is crucial to achieve the decomposition of α' martensite and improve the ductility. However, the reverse transformation behavior and its mechanism of the β phase, as well as its stability remain unclear. Our findings demonstrate that the reverse transformation behavior of the β phase follows a diffusion-controlled process. The decomposition of α' martensite into α + β initiates at approximately 550 ℃, while the transformation from α to β phase occurs around 870 ℃. Increasing temperature leads to an increase in reverse-transformed β phase. The retention of these reverse-transformed β phases at room temperature also depends on their stability, which exhibits a significant correlation with V element partitioning. Additionally, this study reveals a critical temperature (840 ℃) at which the maximum volume fraction (18.6 %) of retained β phase is obtained, exhibiting exceptional mechanical properties, particularly the uniform elongation surpassing those observed in an as-printed microstructure of LPBF-ed Ti-6Al-4V alloy.

Additive manufacturing of Ti-6Al-4V alloy via laser powder-bed fusion leads to non-equilibrium α′ martensitic microstructures, with high strength but poor ductility and toughness. These properties may be modified by heat treatments, whereby the α′ phase decomposes into equilibrium α+β structures, while possibly conserving microstructural features and length scales of the α′ lath structure. Here, we combine experimental and computational methods to explore the kinetics of martensite decomposition. Experiments rely on in-situ characterisation (electron microscopy and diffraction) during multi-step heat treatment from 400∘C up to the alloy β-transus temperature (995∘C). Computational simulations rely on an experimentally-informed computationally-efficient phase-field model. Experiments confirmed that as-built microstructures were fully composed of martensitic α′ laths. During martensite decomposition, nucleation of the β phase occurs primarily along α′ lath boundaries, with traces of β nucleation along crystalline defects. Phase-field results, using electron backscatter diffraction maps of as-built microstructures as initial conditions, are compared directly with in-situ characterisation data. Experiments and simulations confirmed that, while full decomposition into stable α+β phases may be complete at 650∘C provided sufficient annealing time, visible morphological evolution of the microstructure was only observed for T≥700∘C, without modification of the prior-β grain structure.

Overload failure under coupling conditions of elevated temperature and combined tension-bending (CTB) is one of the typical failure modes of aero-engine low-pressure compressor blade materials, which is commonly occurring in fighter engines performing low-altitude high-speed penetration missions. In this study, the elasto-plastic deformation behavior and fracture mechanism of Ti–6Al–4V titanium alloy under coupling conditions of elevated temperature and CTB were investigated by experiments and finite element analysis (FEA). CTB tests were conducted on Ti–6Al–4V alloy in the pre-tension ratio range of 0.60–0.90 and in the temperature range of 298 K–573 K. The results show that the maximum bending load, effective bending modulus, and total energy dissipated for the Ti–6Al–4V alloy at room temperature increase with the increase of the pre-tension ratio. The maximum bending load and the energy dissipated are significantly higher at elevated temperatures compared to that of room temperature, due to the elevated temperature induced deformation mode change from bending-dominated to tensile-dominated. The FEA results are in good agreement with the experimental results. SEM fractography indicated that the Ti–6Al–4V alloy fracture at elevated temperature showed only equiaxed dimples, which exhibited a tensile fracture mode. This study is valuable for the in-depth understanding of the deformation behavior and fracture mechanism of blade materials under elevated temperature and complex loads.

Titanium alloys fabricated by wire and arc additive manufacturing (WAAM) are prone to produce defects with coarse intracrystalline α lamellae, continuous grain boundary of α phase (GB-α), and chemical segregation. The synergistic combination of the factors leads to high strength at the expense of plasticity. Adding activating flux of CaF2 during WAAM can provide an effective way to achieve a remarkable strength-ductility combination of Ti–6Al–4V alloy. Adding CaF2 produced refined intragranular α lamellae, discontinuous GB-α with dowel-like α lamellae (DL-α, primary α phase penetrated through the GB-α and embedded within adjacent β grains), as well as achieved concentration modulations. The tailored microstructure induced multistage strain hardening behavior (sequentially activated multiple strain hardening) during tensile plastic deformation, which allows WAAM-fabricated Ti–6Al–4V alloy a high tensile strength with good plasticity. The good strength-ductility balance is mainly attributed to the utilization of multiple strengthening mechanisms in titanium alloys. This study provides a novel method to improve the mechanical properties of WAAM-fabricated titanium alloys.

Gradient nanograin (GNG) metals possess outstanding resistance to sliding friction and wear. The tribolayer plays a major role in the wear performance of metals. However, the current understanding of the tribolayer in GNG metals is still limited. In particular, some GNG metals show low wear resistance under high contact stress. Here, we investigate the wear behavior of coarse grain (CG) and GNG Ti–6Al–4V alloys and its impact on the wear resistance by sliding contact experiments in combination with finite element modeling. We have found wear-induced the oxidation tribolayer with amorphous structures in GNG Ti–6Al–4V alloy for the first and its impact on wear behavior. It is found that the wear damage mainly occurs in the oxidation tribolayer with amorphous structures, which can generate micro-cracks in Ti–6Al–4V alloy. The wear behavior, including wear resistance, wear micro-cracks, and subsurface structural transformations, is stress-dependent, which can be divided into two distinct regimes-elastic and plastic. Coarse grains (CGs) can form the oxidation tribolayer with amorphous structures in elastic and plastic regimes. Compared to CGs, gradient nanograins (GNGs) can suppress the formation of the oxidation tribolayer with amorphous structures and have higher wear resistance in elastic regime, while GNGs form the oxidation tribolayer with amorphous structures more quickly and have lower wear resistance in plastic regime. This work forges the links between stress-dependent subsurface structural transformations and wear resistance for GNGs, and may provide guidance for the wear application of GNG metals.

Welding processing is an important method to connect precision component, but the internal stress and crystal anisotropy reduce its performance, which are difficult to solve due to the specific demand on regional post-treatment. In the present research, the asynchronized laser shock peening (ALSP) and synchronized laser shock peening (SLSP) processing technologies were applied to treat the laser joined Ti–6Al–4V thin plates. The microstructure and mechanical properties of the as-welded joint, ALSP and SLSP processed joint were investigated. The results revealed that the as-welded joint presents obvious anisotropic characteristics, and high strain level exists on the prior β grain boundary, which causes stress concentration. The ultimate tensile strength (UTS) and elongation (EL) values of as-welded joint just reach the 92.18% and 72.33% of as-received plate, respectively. ALSP processing could result in the deformation with the depth more than ten microns and introduce compress stress in the top layer, but has little effect on decreasing the anisotropy. The grain boundary becomes obscure and the strain distribution is relatively uniform, accompanying with some dynamic recrystallized laths exist along the grain boundary. Its values of UTS and EL are 5.23% and 5.59% higher than as-welded joint, respectively. With the SLSP processing, the deformation depth exceeds twenty microns, and the crystal isotropy could be greatly promoted. Moreover, higher compressive stress is introduced from top layer to center area of joint. The grain boundary becomes obviously obscure, which is completely replaced by recrystallized lath structures. The residual strain in the top layer is partly eliminated, and the stress concentration phenomenon along grain boundary is dramatically decreased. The UTS and EL values are 6.16% and 20.58% higher than as-welded joint, and reach 97.86% and 87.22% of as-received plate, respectively.

Ti–6Al–4V alloy, as a typical difficult-to-machine material, is prone to problems such as large cutting forces, high cutting temperatures, and serious tool wear during the cutting process. Ti1-xAlxN coated tools are widely used in machining Ti–6Al–4V alloys. The main wear forms of Ti1-xAlxN coated tools are coating cracking and delamination. After the coating has been delaminated, the tool substrate is in direct contact with the workpiece material, aggravating tool wear and shortening the tool life. Therefore, the milling process of Ti1-xAlxN coated tool cutting Ti–6Al–4V alloy was performed using FEM. The effects of Al contents (Ti0·48Al0·52N, Ti0·38Al0·62N), coating thickness (2, 3, 4 μm), and tool substrate (Cemented Carbide Grade K, M, P) of Ti1-xAlxN coated tools on the cutting performance (cutting force, cutting temperature, maximum principal stress, the temperature and stress of coating-substrate interface) and tool wear were discussed. The influence of the maximum principal stress, the temperature and stress of coating-substrate interface on tool wear were analyzed. This paper can provide a reference for the design and optimization of Ti1-xAlxN coated tools by investigating the wear of Ti1-xAlxN coated tools cutting titanium alloys, which can be used to slow tool wear and prolong tool life.

Dry machining of Titanium alloy Grade 5 (Ti–6Al–4V) with cryogenic treated, double-tempered KC5010 cutting inserts was examined. The impact of cryogenic treatment followed by tempering of the carbide inserts was investigated using microstructure analyses. The effects of constant depth of cut, cutting speed, and feed rate on machining variables (torque, force, surface roughness, temperature, and tool wear) were investigated. According to the experimental results, the cutting speed is the most important parameter that has a direct influence on the machining characteristics. Increased cutting speed and feed rate generate larger tangential pressures, allowing for a reduction in chip contact length; a shorter contact length results in reduced surface roughness and flank wear rate, respectively. The effects of cutting speed and feed rate on chip thickness were studied. Image analysis of the segmented chip was used to investigate the form and size of the saw-tooth profile of serrated chips. It was discovered that raising the cutting speed from 73 m/min to 160 m/min enhanced the free surface lamella of the chips and improved the visibility of the saw tooth segment. As cutting speed increases, all response parameters (torque, temperature, force, tool wear, and surface roughness) increase at the same time, by nearly 300%. Deep cryogenic treatment enhanced micro-hardness, resistance to wear, and toughness. As a result, there was reduced flank wear with tiny abrasion lines. Lower cutting speeds and feed rates resulted in less rake surface wear. Finally, the current study's convergence with earlier research was presented, indicating strong agreement between the two examinations.

To address the challenges associated with preparing thin strips of difficult-to-deform materials – such as low processing efficiency and yield, poor shape, and subpar performance – our research team developed an on-line warm rolling experimental machine featuring hydraulic tension. We used the Ti–6Al–4V alloy as our experimental material and conducted warm rolling experiments at various temperatures, thoroughly examining the intricate relationship between microstructure evolution and mechanical properties. Our findings indicate that warm rolling causes a clear refinement of the α phase and β phase microstructures, while intensifying dislocation entanglement. These changes significantly enhance the strength of the Ti–6Al–4V alloy, though Total Elongation Limit (TEL) decreases. After evaluating mechanical properties, surface quality, and energy consumption associated with warm rolling, we determined the optimal warm rolling temperature for the Ti–6Al–4V alloy to be 650 °C. At this temperature, the Ultimate Tensile Strength (UTS), Yield Strength (YS), and TEL were 1325 MPa, 1164 MPa, and 8.0%, respectively, maintaining good ductility. The impressive performance of the Ti–6Al–4V alloy sheet is mainly attributed to the strengthening effects of fine grain and dislocation, while the introduction of some fine recrystallization enhances ductility. High-performance Ti–6Al–4V alloy thin strip was successfully prepared by on-line warm rolling with hydraulic tension, which provided a new idea for the preparation of thin strip of difficult-to-deform materials.

Titanium alloys have been used extensively as implants. However, they generally suffer from low biocompatibility as well as antibacterial activity. To date, several strategies have been proposed to address these issues. It is of practical interest to synergistically increase both cellular adhesion and antimicrobial activity in titanium-based implants. Here, Ti–6Al–4V alloys were surface-modified by Nd:YAG laser with different scanning speeds ranging from 1 to 5 mm s−1 and subsequently coated by drug-loaded polymer nanofibers for prolonged drug release. The laser-modified samples were both physically and metallurgically characterized through XRD, OM, AFM, FESEM, hardness, and wettability tests to find the optimum laser processing conditions. Results showed that the surface characteristics of the alloys are sensitive to the scanning speed; the higher the scan velocity, the lower surface roughness and wettability were obtained. The enhanced formation of TiO and Ti6O oxides on the surfaces of laser-modified alloys was delineated. Then, a model polymer/drug system of polyvinyl alcohol/vancomycin was directly electrospun onto the optimized samples surfaces. The laser-modified, drug-loaded samples present an improved biocompatibility as the cellular adhesion and viability were increased in contact with these samples. Up to 39% increase in cell viability was obtained for the laser-modified samples by 5 mm s−1 scan speed in comparison with unmodified, uncoated samples. The increased biocompatibility was attributed to the formation of oxide layers which reduce the toxicity of vanadium and aluminum elements. Also, the drug release rate was extended from 4 h to 25 h for modified samples. So, the modified implants could present a sustained release of antibiotics as well.

This work proposes an oscillating wire laser additive manufacturing (O-WLAM), which is based on the wire laser additive manufacturing technology (WLAM) and combined with the laser oscillating welding technology. For different laser oscillation patterns, it shows a trend that metallurgical defects such as porosity, microstructural and columnar grain size decrease with the increase of oscillation frequency and oscillation amplitude. In solidified grains formed under laser oscillation, a complex oscillation of melt pool agitation could lead to a refining effect on the β grains size. The corresponding tendency of epitaxial growth of the prior β grains is weakened as well. The process experiments in this work provide a new idea of laser oscillation for wire laser additive manufacturing. The use of laser oscillation to achieve improvement of metallurgical defects and optimization of microstructure has some guiding significance for wire laser additive manufacturing.

Ti-based alloys fabricated by wire and arc additive manufacturing (WAAM) exhibit continuous grain boundaries of α phase (GB-α), which easily initiate cracks and provide a continuous crack propagation path. Herein, an activating flux of CaF2 particles was introduced into WAAM-fabricated Ti–6Al–4V alloy to tailor the microstructure for crack buffering (i.e., inhibit smooth propagation of cracks). The results showed that the addition of CaF2 particles disrupted the continuous GB-α through the dowel-like lamellar α phase (DL-α), which was primary α lamella deeply embedded in the adjacent prior-β grains. This microstructure imparted an optimal combination of strain and strength even in the presence of pores in the WAAM-fabricated Ti–6Al–4V alloy. The enhanced mechanical properties can be attributed to uniform plastic deformations and tendency to transgranular fracture of tensile specimens. DL-α relieved stress concentration at the grain boundary and guided cracks into the prior-β grain interior (i.e., avoided inter-crystalline fracture), thereby promoting the crack buffering effect. The study can provide theory guidance and data support for improving the mechanical performance of WAAM-fabricated Ti–6Al–4V alloy.

The solution and aging treatment were carried out with the hot rolled sheet Ti–6Al–4V alloy sheet, and the effects of solution treatments on the microstructure and mechanical properties were mainly studied. In the solution treatment process, α→β→βt transformation occurred. With the increase of solution treatment temperature and time, the α phase gradually changed from long strip to equiaxed morphology, and the fraction of equiaxed α and β phases gradually increased. The bimodal microstructure of αp and βt was obtained during the solution treatments. Among them, βt is mainly composed of high-density nano-needle αs with different orientations, which has a significant contribution to the strength of Ti–6Al–4V alloy. The strength of bimodal microstructure increases with the increase of βt content, but its influence on ductility is complicated. When βt content exceeds a certain amount, it is easy to lead to brittleness. It is found that when the specimens are treated at 930 °C for 60min or 960 °C for 30min, the best strength-ductility matching can be obtained. In this case, the volume fractions of αp and βt are almost equal, and the PSE of Ti–6Al–4V alloy reaches more than 14500 MPa⋅%.

Micro-voids defects associated with materials formed by diffusion bonding and super-plastic connection limit their usage in the aerospace industry. A crystal plasticity finite element (CPFE) model was established in the current work to investigate the relationship between local stress concentration and the micro-void defects, and predict the fatigue crack initiation lifetime. Based on the concept of the curvature of the crack tip, the shape and size of the voids are strictly separated, so that the influence of the single parameter of voids on the microplasticity deformation behavior is better obtained. It's found that the micro-voids lead to the stress concentration phenomenon in the material, the effect of the curvature of the void tip surface is greater than that of the void size. Stress concentration tends to occur in the hard grains. When L/d is greater than 2.0, stress concentration factor reaches a constant small value. The simulated results based on the Manson-Collin law and Fatemi-Socie parameter show that when the void tip curvature is greater than 0.4 μm−1 or L/d is less than 2.0, the fatigue crack initiation lifetime is less than 106 cycles, indicating that the influence of such micro-voids on fatigue crack initiation is small. This work has a good guiding significance for properties and lifetime prediction of the material with defects.

The aim of this study was to reduce the number of defects, refine the grain size, and improve the mechanical properties of Ti–6Al–4V. We investigated the effect of interpass micro-rolling on the microstructures and mechanical properties of Ti–6Al–4V alloys produced via plasma arc additive manufacturing (PAAM). The non-rolled plasma-arc additively manufactured (PAAMed) sample exhibited coarse columnar crystals, basket-weave microstructures, and Widmanstätten structures, while the interpass-micro-rolled PAAMed sample exhibited fine equiaxed crystals and basket-weave microstructures. Interpass micro-rolling could significantly reduce the number density and size of defects during PAAM, and the rolled samples exhibited lower mechanical property anisotropy than the non-rolled samples. Moreover, the rolled sample exhibited a higher yield strength (∼797.66 and 793.45 MPa), tensile strength (∼939.73 and 935.71 MPa), and elongation (∼12.83% and 14.73%) in the X- and Z-directions than the unrolled sample. These enhanced mechanical properties can be attributed to αGB fragmentation, grain boundary strengthening, dislocation strengthening, and a low crack density. The micro-cracks preferentially nucleated around defects in the non-rolled sample, resulting in high crack and defect densities.

An effective cooling mode with appropriate process parameters can enhance the machinability as well as productivity. In this regard, this study focuses on evaluating the machinability of widely used Ti–6Al–4V alloy with the use of high-pressure coolant jets compared to dry milling. A novel rotary applicator was designed and developed to feed high-pressure coolant jets without any drastic change of solid end mill cutter. Four flutes solid HSS end mill cutter was selected for machining because of its some intensive properties. Biodegradable VG-68 cutting oil was chosen as cutting fluid due to its better thermo-physical properties with higher flash points. Machinability was assessed at 16–32 m/min cutting speeds and feed rates of 0.08–0.16 mm/tooth with a constant depth of cut of 1.0 mm, taking into account the average cutting temperature, resultant cutting force, mean surface roughness, and tool wear. Dry milling produced the worst results for all of the investigated responses, with excessive tool wear due to the lack of cooling and lubrication. Compared to dry milling, high-pressure cooling (HPC) lowered average cutting temperature, resultant cutting force, and mean surface roughness by 11.21–21.57%, 8.63–13.12%, and 6.09–29.6%, respectively, whereas rotary high-pressure cooling (RHPC) reduced these parameters by 15.39–27.27%, 14.05–21.18%, 16.48–41.04%. RHPC's efficient cooling and lubrication increased the machinability of the Ti–6Al–4V alloy. Dry milling showed severe flank wear with increased built-up edge (BUE) development, abrasion, and adhesion, whereas HPC and RHPC dramatically reduced the severity of tool wear. In HPC and RHPC, the tool life was consequently increased by 6.8 and 9 min, respectively.

The flow behavior of a Ti–6Al–4V alloy during warm forming was characterized, and the results were analyzed to reveal the causes of fracture during warm forging of a small Ti–6Al–4V alloy bolt. The experimental flow curves obtained by compression test of cylindrical specimens at the warm forming conditions were fitted by a general extended C–m model after post-processed by a high-accuracy temperature correction scheme. Finite element analyses of the compression tests were conducted at various sample temperatures and strain rates using the flow model, revealing that the predicted compression loads were consistent with the experimental results. Flow behavior was also analyzed to reveal the metallurgical and macroscopic instabilities of the Ti–6Al–4V alloy. The flow behavior, macroscopic instability indices, and predicted forming load-stroke curves of Ti–6Al–4V alloy and SCr420H alloy steel were compared. The results study revealed that fracturing of the material in the capping stage during the automatic multi-stage warm forging of the small Ti–6Al–4V alloy bolt was caused by the sharp decrease in the forming load in an unpredictably early stroke from macroscopic instability, as indicated quantitatively by its macroscopic instability index.

The most popular additive manufacturing (AM) technologies to produce titanium alloy parts are electron beam melting (EBM), selective laser melting (SLM) and directed energy deposition (DED). This investigation explores mainly these three techniques and compares these three methods comprehensively in terms of microstructure, tensile properties, porosity, surface roughness and residual stress based on the information available in the literature. It was found that the microstructure is affected by the highest temperature generated and the cooling rate which can be tailored by the input variables of the AM processes. The parts produced from EBM have strength comparable to that of conventionally fabricated counterparts. SLM and DED yield superior strength, which can be up to 25% higher than traditionally manufactured products. Due to the presence of larger tensile residual stress, surface roughness and porosity, AM fabricated parts have lower fatigue life compared to those of from traditional methods. EBM parts have slightly lower fracture toughness (i.e., lower fatigue life) than conventionally produced parts while SLM and DED have significantly lower fracture toughness. Annealing, hot isostatic pressing, stress relief and additional machining processes improve the characteristics of parts produced from AM. Ti–6Al–4V alloy parts fabricated via AM may have limited applications despite the high demands in aerospace or biomedical engineering. Since rapid product development using 3D printers leads to significant cost reductions more recently, it is expected that more opportunities may soon be available for the AM of titanium alloys with newer AM processes such as cold spray additive manufacturing (CSAM) and additive friction stir deposition (AFSD).

The hot flow behavior, spheroidization, dynamic recrystallization (DRX) and fusing of lamellar ɑ phase for hot isostatic pressed Ti–6Al–4V titanium alloy was investigated at 950°C-900°C–850 °C with the total deformation amount of 70% during multi-pass deformation. The results show that all the flow stress value presented a peak value, followed by different flow softening extent. The flow stress is very susceptible to deformation parameters such as strain, strain rate and deformation temperature, and also the peak value decreased as the increase of temperature and the decrease of strain rate. The main softening mechanisms for different deformation pass are the DRX of β phase for one-pass deformation, spheroidization of lamellar α phase for two-pass deformation and DRX of α phase for three-pass deformation, respectively. The lamellar α spheroidization deformed in two-pass at 900 °C increased with decreased strain rate or the increased strain, and the maximum spheroidization fraction of lamellar α phase was 43% at 0.01s−1. The spheroidized mechanism of lamellar α phase is major give rise to the combined action of kinking deformation and element diffusion. Nevertheless, in the three-pass deformation process, the spheroidization degree did not significantly increase as increased strain, which principal give rise to the fusion of the same orientation of lamellar α phase. The fusion mechanism is the result of the joint action of the orientation of lamellar α phase and dislocation slip. And, the fraction of DRX of α phase is obviously higher than that of spheroidization in three-pass deformation, which is the main softening mechanisms.

Ti–6Al–4V alloys prepared via electron beam powder bed fusion (EB-PBF) generally exhibit a hierarchical microstructure consisting of columnar β-grains, an acicular α-matrix, and nanoscale β-precipitates at α-lath interfaces. In this study, we performed time-of-flight neutron diffraction measurements to investigate the texture and volume fraction of EB-PBF Ti–6Al–4V alloys via Rietveld texture analysis (RTA). The high-intensity neutron source enabled the analysis of the nanosized β-phase precipitates at the α-lath interfaces. The results indicate that the α- and β-textures of the as-built specimen can be ascribed to multiple Burgers orientation relationships among the prior β-phase, α-laths, and nanosized β-phase precipitates, which are not clearly understood. The as-built texture was maintained during post-processing, suggesting that texture manipulation in EB-PBF fabrication is important for controlling the crystallographic orientations of the built components, even after post-processing. RTA allowed a precise quantification of the β-phase fraction, which was found to have increased in post-processed specimens. The results would contribute to a comprehensive understanding of the microstructural evolution of such alloys, which is vital for the modeling and optimization of alloy performance.

A gradient microstructure was successfully fabricated by high-frequency induction quenching treatment (HFIQT) to improve the mechanical behavior of Ti-6Al-4V alloy in this work. Microstructural evolution was systematically characterized by electron backscattered diffraction and transmission electron microscopy. The results showed that the gradient microstructure of the alloy after HFIQT and aging varied from a fine αs lamellae decomposed from α′-martensite at the surface layer to a bimodal microstructure at the center. Moreover, the alloy with gradient microstructure presents an optimal strength-ductility synergy. The tensile test results showed that a best strength plastic product UT of 12433.1 MPa·%, an ultimate strength of 1231 MPa and an elongation of 10.1 % were obtained after HFIQT for 5.2 s and aging at 400 °C for 6 h. The tensile strength of the alloy aged at 400 °C markedly increased with the increase in soaking time from 5.1 to 5.3 s during HFIQT. Meanwhile, the tensile strength of the alloy slightly increased with the decrease in aging temperature from 550 to 400 °C during HFIQT. Surprisingly, the elongation of the alloy also increased with decreasing aging temperature. The effects of the gradient microstructure characteristic on strength and ductility of the Ti-6Al-4V alloy were discussed.

Titanium alloys require a special protecting atmosphere during the fabrication process due to their strong affinity with oxygen and nitrogen elements at high temperatures. In this study, the effects of different protection conditions on microstructure, phase characteristics, interstitial elements absorption and microhardness of additively manufactured Ti–6Al–4V alloy by direct laser deposition method have been investigated. Fabrication of specimens with similar laser parameters was carried out in three different protection conditions consist of air, closed box and argon shower. Characterization of samples was performed by utilization of OM, SEM, XRD, inert gas fusion method, micro-hardness and tensile strength analysis. Results indicated that fabrication of samples in an air atmosphere without proper protection leads to 2.5% spherical porosities, TiO2 and TiN formation in top layers, changing the c/a ratio from 1.59 to 1.61, absorption of 1870 and 500 ppm oxygen and nitrogen and 155 HV increment in micro-hardness value. Also, uncommon semi-globular microstructure in different locations of samples has been observed. The special protective atmosphere provided by argon shower led to 6.3% spherical porosities, negligible lattice parameter variation and martensite microstructure formation. It was found that in the optimal protection condition that was provided by a closed box, the typical basketweave microstructure with less than 1% porosity and 960 and 140 ppm oxygen and nitrogen absorption were achieved, which did not exceed the standard limits. In addition, the mechanical properties of UTS tensile strength, yield strength and elongation, were obtained 1042, 893 MPa and 13.2% respectively.

The ultrasonic shot peening (USP) treatment was adopted to improve the compressive residual stress, microhardness and corrosion resistance of Ti–6Al–4V (TC4) titanium alloy fabricated by selective laser melting (SLM). The optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and hardness test were used to investigate the microstructure evolution. The effect of the USP on electrochemical behaviour of the SLM TC4 alloy in a 3.5 wt. % NaCl solution was studied using potentiodynamic polarization. After USP treatment, compressive residual stress was induced and microhardness significantly increased. Proper USP treatment can effectively improve corrosion resistance of the SLM TC4 alloy, which is manifested by the increase in corrosion potential and decrease in corrosion current density.

In this paper, the effect of hydrogen on the interfacial reaction between Ti-6Al-4V (Ti64) alloy and graphite casting mold was studied by argon and hydrogen plasma arc melting. The experimental results showed that the thickness and the hardness of the interfacial reaction layer decreased with increasing hydrogen partial pressure. The interaction of activated H atoms in the titanium alloy melt and carbon on the interface, [C] + 4[H] = CH4, could be taking place.

Different energy densities in Selective Laser Melting produce different metallurgical properties of the product surface, which include adhered powder particles, waviness, porosity, and microstructure. In this research, the corrosion behavior of these structural properties was investigated and compared with heat-treated samples. The size and arrays of α'-martensitic varied significantly due to the effects of different cooling rates and the number of effective thermal cycles caused by different scanning speeds and energy densities. The surface particles experienced different thermal effects that significantly changed their microstructure with each other and with respect to the main surface, which remarkably affected the corrosion properties. The densities, hardness, and tensile properties of the samples were also presented and interpreted their relations with corrosion. These correlations between the metallurgical and corrosion properties of SLM products support biomedical engineers in the further development of bespoke medical devices, especially implants.

The present study investigated the sensitivity of material constitutive models on thermomechanical responses in laser powder bed fusion additive manufacturing of Ti-6Al-4V. Uniform scan strategies with scan lengths of 0.5, 1, and 2 mm were applied so that wide ranges of thermal histories could be generated. The Johnson-Cook (JC) and Mechanical Threshold Stress (MTS) material plasticity models were chosen to capture the influence of strain, strain rate, and temperature. The JC model is a phenomenological model which is known for its easy implementation and excellent agreement with material testing results. On the other hand, the MTS model is a more complex physics-based internal state variable plasticity model that is expected to provide more accurate estimation, particularly for cases involving changes in strain rate and temperature. Numerical results revealed that both JC and MTS models provided a similar stress evolution, however, the plastic strain evolution was more realistic using the MTS model. Moreover, it was found that the maximum strain and the strain rate in the LPBF process are high compared to typical quasi-static testing, i.e., ~ 2% and ~ 4 s−1, respectively. Accordingly, the material models should be calibrated with data obtained under similar deformation conditions. The choice of scan length also strongly affects in-plane stress anisotropy. Ultimately, we show both qualitatively and quantitatively the dependency of mechanical behavior prediction in LPBF on the choice of material models.

The formation of the coarse columnar crystal structure of Ti-6Al-4V alloy in the process of additive manufacturing greatly reduces the mechanical performance of the additive manufactured parts, which hinders the applications of additive manufacturing techniques in the engineering fields. In order to refine the microstructure of the materials using the high intensity ultrasonic via the acoustic cavitation and acoustic flow effect in the process of metal solidification, an ultrasonic vibration technique was developed to a synchronous couple in the process of Laser and Wire Additive Manufacturing (LWAM) in this work. It is found that the introduction of high-intensity ultrasound effectively interrupts the epitaxial growth tendency of prior-β crystal and weakens the texture strength of prior-β crystal. The microstructure of Ti-6Al-4V alloy converts to fine columnar crystals from typical coarse columnar crystals. The simulation results confirm that the acoustic cavitation effect applied to the molten pool created by the high-intensity ultrasound is the key factor that affects the crystal characteristics.

The improvement of the density with functional microstructure is still a challenge in the Selective Laser Melting process considering the laser processing parameters. In this study, the pore formation mechanisms and microstructural changes caused by the effects of laser power and track overlap during the manufacturing process in selective laser melting were examined. Laser power played a crucial role in the geometry and quantity of keyhole pore formation and thus in improving density and quality. In contrast, a slightly higher track overlap led to a significant reduction in porosity, resulting in the production of fully dense samples of a Ti-6Al-4V alloy. The gradual variations in the solid-state phase transformation architecture occurred with variations in laser power and track overlap due to the use of different thermal mechanisms. The associated scanning speeds also significantly affected the microstructural architectures in some states. The melt pool dynamics and thermal properties that influenced the metallurgical properties of the samples are analyzed and interpreted. The analysis of the presented consequences can help the engineers to produce high density products together with functionally graded materials.

The CaO–MgO–SiO2-based bioactive glass-ceramic coating (named M2) on Ti–6Al–4V alloy has been proven to behave well in vitro. But how to make full sense of its performances in terms of osteogenesis and osseointegration in vivo matters very much. For this, the M2-coated Ti–6Al–4V cylinders were prepared by atmospheric plasma spraying (APS) and implanted into New Zealand rabbit for 1, 2 and 3 months, respectively, by setting commercial HA-coated Ti–6Al–4V as the control. It is encouraging that, the two groups bonded with the surrounding tissues stably and newly formed bone grew towards or around the implants after 3-month implantation according to radiographic images. From the histological sections, it is obvious that, compared to the control, the M2-coated implant was more favorable for the osteogenesis and neo-vascularisation in the whole experimental process and demonstrated a better osseointegration with the host bone, indicating the former possessed better osteoconductivity, osteoinductivity and osteogenic ability. The study indicated that the M2-coated Ti–6Al–4V implant exerted a great potential to substitute the commercial HA-coated Ti–6Al–4V implant in repairing load-bearing bone defects.

In this paper, inorganic phosphate bonded coatings (IPBCs) via embedding reduced graphene oxide (rGO) modified with heptadecafluoro-1,1,2,2-tetradecyl trimethoxysilane (FAS) were prepared through sol-gel method. Aim of this paper is to research the corrosion resistance of IPBCs with the addition of rGO modified with FAS. Firstly, the Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman) and surface morphology of GO and rGO modified with and without FAS were characterized. Results indicated that the hydrophobic -CF 2 - and -CF 3 groups were successfully introduced into GO and rGO after modification. And IPBCs with rGO-FAS exhibited higher hydrophobicity and corrosion resistance than IPBCs with the addition of GO or GO-FAS. That is because the hydrophobicity and the introduction of low surface energy material is conducive to overcoming the interaction of rGO itself, thus rGO can be better utilized and played, which resulting the excellent corrosion performance of IPBC@rGO-FAS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this paper, Taguchi method was employed to optimize the surfactant and graphite powder concentration in dielectric fluid for the machining of Ti-6Al-4V using Electrical Discharge Machining (EDM). The process parameters such as discharge current, surfactant concentration and powder concentration were changed to explore their effects on Material Removal Rate (MRR), Surface Roughness (SR), Tool wear rate (TWR) and Recast Layer Thickness (RLT). Detailed analysis of structural features of machined surface was carried out using Scanning Electron Microscope (SEM) to observe the influence of surfactant and graphite powder on the machining process. It was observed from the experimental results that the graphite powder and surfactant added dielectric fluid significantly improved the MRR, reduces the SR, TWR and RLT at various conditions. Analysis of Variance (ANOVA) and F-test of experimental data values related to the important process parameters of EDM revealed that discharge current and surfactant concentration has more percentage of contribution on the MRR and TWR whereas the SR, and RLT were found to be affected greatly by the discharge current and graphite powder concentration.

A cold-rolled Ti-6Al-4V sheet was subjected to three different heat treatments prior to processing by high pressure torsion (HPT). Quantitative measurements revealed that the volume fractions were 70% equiaxed α phase and 30% lamellar (α + β) (Ti64-1), 47% equiaxed α phase and 53% lamellar (α + β) (Ti64-2) and 25% equiaxed α phase and 75% lamellar (α + β) (Ti64-3) and the grain sizes of the α phase were 7.0 ± 2 μm, 9.0 ± 1.5 μm and 9.5 ± 1.5 μm, respectively. The processing by HPT was performed at room temperature with a pressure of 6.0 GPa and a rotation speed of 1 rpm. Processing of the three heat treatment batches was conducted through a total number of revolutions, N, of 1/4, 1, 5, 10 and 20. The results show that the microhardness increases with increasing numbers of turns in HPT processing and for all three conditions stable microhardness values are reached after about 20 turns. The grain sizes after 20 turns of HPT were 115 ± 30 nm in Ti64-1, 85 ± 25 nm in Ti64-2 and 75 ± 15 nm in Ti64-3 so that the grain size decreases as the volume fraction of α phase decreases and the lamellar (α + β) increases.