Processing Of Titanium Alloys Research Articles

Nanocrystallization of a Ti40 cladding layer by ultrasonic impact to improve burn resistance

With the wide application of titanium alloys in the aerospace industry, the burn resistance properties and surface strengthening processes of titanium alloys have been received increasing attention. In this study, Ti40 burn-resistant titanium alloy was cladded on the surface of TC4 by electron beam cladding, and the surface layer of the nanostructure was prepared by ultrasonic impact treatment (UIT). The nanostructure layer was examined by pulse laser ablation. The results showed that when the moving speed was 16 mm/s, the maximum thickness of the plastic deformation zone of the UIT Ti40 cladding layer reached 150 μm. The highest hardness value was 531 HV, which was approximately 43.5% higher than the original microstructure of the Ti40 cladding layer without UIT. Moreover, the surface microstructure of the Ti40 burn resistant titanium alloy cladding layer was nanocrystalline with uniform distribution and random orientation, and the average grain size was 50 nm. The UIT process can effectively increase the relative content of burn-resistant alloy elements on the surface of the Ti40 cladding layer and increase the content of dense oxidation protective films after laser ablation, which hinders the diffusion and migration of oxygen elements to the matrix alloy in the process of ablation and then improves the burn resistance of the Ti40 cladding layer.

Multi-objective titanium alloy belt grinding parameters optimization oriented to resources allocation and environment

Belt grinding is a widely adopted method in processing titanium alloy materials. However, its unique grinding mechanism will greatly affect grinding efficiency. Meanwhile, in order to finish processing task, adopting the method of replacing belts frequently will further make processing time, cost, and energy consumption rise, as well as the pollution during the whole processing. Considering the problems above, first, establish a multi-objective optimization model, which takes spindle rotary speed, feed speed of workpiece, grinding depth, and axial feed as the variables and takes processing time, SEC (specific energy consumption), cost, and environmental impact as objective optimization functions. Secondly, multi-objective particle swarm optimization algorithm is applied to solve resources allocation objectives for Pareto optimal solutions. Then, analytic hierarchy process is applied to analyze the degree of environmental impact of each solution among Pareto optimal solutions and finalize the best optimization solution of belt grinding. Finally, an experiment case is performed to verify the effectiveness of the optimization model. The result shows that, compared with experience-guided parameters, the optimized grinding parameters make processing efficiency improve by 17.3% and SEC declines by 13.2% cost decline by 17.0%. The proposed optimization method of grinding parameters is effective and can be applied to engineering practice. Meanwhile, it can provide a reference to the selection of grinding processing parameters.

Recent advances in processing of titanium alloys and titanium aluminides for space applications: A review

The results of untiring efforts by the research community over the past few decades have led to the successful development and processing of a number of advanced titanium alloys with widely varying properties that can cater to niche applications. Advanced titanium alloys on one hand challenge structural steels with their higher specific strength coupled with their low temperature capability down to 4 K and pose serious threat on the other hand to superalloys for long-term applications up to 773 K. An improved understanding of the processing-microstructure-mechanical property correlation led to the realization of large scale as well as performance critical titanium alloy products in space arena. Recent advances in additive manufacturing, wherein the desired components are directly 3D printed from pre-alloyed powders/wires have given a definite advantage for cost-prohibitive titanium alloys. This review article discusses challenges in the processing, mechanical properties and microstructure evolution of various grades of titanium alloys. It also provides useful information for researchers working on titanium alloys with a glimpse in to the recent advances in Ti alloys and transformation of scientific knowledge to technological advancements in products for space applications.

Microstructure Evolution during Multiaxial Processing of TA6V

Subtransus multiaxial hot forging of α+β Ti-6Al-4V (TA6V) titanium alloy with a β-transformed microstructure aims at obtaining an equiaxed microstructure through α phase globularization. The activation of mechanisms involved in microstructural evolution, such as globularization, depends on parameters such as time, temperature, strain and strain rate. It is also sensitive to the crystallographic orientation of α-lamellae. As a result, multiaxial processing of titanium alloys leads to significant microstructural gradients depending on thermomechanical conditions and initial microstructure. In this study, we focused on the effect of complex thermomechanical paths on microstructural evolutions. Thanks to the MaxStrain Gleeble device, we were able to reproduce such thermomechanical treatments to β-transformed TA6V samples. Stress strain fields obtained with finite element modelling of the MaxStrain test were compared to experimental microstructure gradients. This experimental method offers the opportunity to get closer to industrial open die forging conditions.

Cleaner milling on Ti-6Al-4V alloy cooled by liquid nitrogen: external spray and inner injection

In titanium alloy processing, the cutting fluid often expresses the environmentally unfriendly, high-cost, and limited-quality improvement and affects their future application prospects. At present, liquid nitrogen (LN2) cooling could play a green manufacturing role and is being popularized for difficult-to-machine materials. In this paper, an LN2 inner injection transmission device was fabricated. A series of processing tests were carried out by comparing the LN2 external spray method and cutting fluid. And the different effects of the two LN2 cooling methods on the machining accuracy, required liquid nitrogen flow, machinability, and tool wear were investigated. The results show that the cryogenic of LN2 can significantly improve the thermal and force coupling action conditions in titanium alloy processing than cutting liquid cooling. Compared with higher cutting zone temperature of cutting liquid cooling, it is lower than 0° C for LN2 cooling even at 300-m/min cutting speed. When the required cooling temperature is lower, the external spay method needs more than 200% flow than the inner injection. Meanwhile, the diameter of 6-mm spray nozzle should be selected to be the more effective one for the external spray method. Moreover, the tool life can be more than 200% in LN2 cooling, especially the inner injection cooling is 10% longer than that of the external spay one. The milling force of external spay cooling is increased compared with inner injection. Furthermore, the inner injection cooling of LN2 has more efficiency, environment friendliness, and cleaner production for the machinability of difficult-to-machine materials.

Research on the water cavitation peening process and mechanism of TC4 titanium alloy

Cavitation water shot peening is a new processing method of surface strengthening and modification that utilizes the cavitation bubbles in the cavitation water jet to destroy high-energy shock waves, causing the cavitation groups to collapse on the surface of the material. Strengthening research on TC4 titanium alloy cavitation water jet peening is limited. The process of cavitation water shot peening strengthening is small, and the mechanism of residual stress generation is not yet clear. Therefore, five typical shot peening strength tests of TC4 titanium alloy are taken as examples in this paper. Experiments and mechanistic studies are carried out through macro-micromorphology, metallographic structure and XRD analysis, microhardness, and residual stress methods. The research results are as follows: as the shot peening strength increases, the surface roughness Ra and the depth of the plastic deformation layer gradually increase, and the depth of the plastic deformation layer is saturated at 55–60 μm; the depth of the influence of the microhardness and residual stress reaches 130 μm; and the surface grains gradually refine and develop to the nanometre level.

The effect of mass transfer between electrodes in the electrospark alloying process of titanium alloys with hard materials

The effect of mass transfer between electrodes in the electrospark alloying process of titanium alloys with hard materials

Evaluation of the tool wear in the turning process of INCONEL 718 using PCD tools

The use of nickel-based alloys (superalloys) has an ever-growing demand because of the combination of mechanical properties and corrosion resistance even at relatively high temperatures. Those same properties, however, increase the challenge to increase the cost-benefit of the machining operations. Nickel superalloys are usually machined using coated cemented carbide inserts at relatively lower cutting speeds or ceramic inserts at higher cutting speeds. The use of PCD tools, despite widespread at the machining process of titanium alloys, regarding the machining of nickel-based alloys has almost no research data, especially for Inconel. This happens mostly because of the alloys’ iron content leading to graphitization of the diamond at the tool. This paper presents a study about the viability of PCD tools in the turning process of Inconel 718 in finishing conditions. The machinability was assessed under different tool rake angles, cutting speeds, feed rates, and minimum lubrication flow rates. The results were compared regarding the specific cutting pressure, average workpiece profile roughness, tool wear and wear mechanisms observed through electronic microscopy. The results indicate that the rake angle did not have a statistically significant influence for the evaluated machining conditions and the feed rate was the most significant parameter, as it is linked with the specific cutting pressure and workpiece roughness. Adhered material seemed to have protected the rake surface from attrition, which reduced the amount of wear particles that promote abrasion of the flank surface. However, the increase in MQL flow seems to destabilize the adhered material and promote more severe wear. Overall, microchipping and adhesion were the most important wear mechanisms.

β-Ti-Based Alloys for Medical Applications

Titanium alloys have been used for medical purposes for over 60 years. They are employed in the manufacture of artificial heart valves, blood vessel stents, and endoprostheses of bones and joints (shoulders, knees, hips, and elbows); for the reconstruction of auricles; in facial surgery; and as dental implants. In first-generation materials (such as technically pure titanium or VT6 alloys), the matrix consisted of α-Ti phase or a mixture of α and β phases. Unfortunately, implants from first-generation materials require replacement after as early as 10–15 years of usage. This is due to the degradation of the implants and loss of contact with the bone. Recently, these materials have been replaced by β-titanium alloys, second-generation materials that make it possible to exclude the harmful effect of aluminum and vanadium ions released during the gradual corrosion of the implant, and their elastic modulus is closer to the values for living bone than those for α and α + β alloys. Important directions in the development of β-titanium alloys include increasing their mechanical strength, fatigue strength, corrosion resistance, and biocompatibility. New methods for the production and thermo-mechanical processing of titanium alloys, such as additive technologies or severe plastic deformation, are created and developed. Expensive alloying elements (such as tantalum, zirconium, or niobium) are very successfully replaced with cheaper ones (for example, chromium and manganese). As a result, the properties of titanium implants are gradually getting closer to those of human bone, and their service life is steadily increasing. In this regard, we have carried out a comparative analysis of β-titanium-based alloys for medical applications.

Phase composition and properties of mao coatings on titanium alloys

Problem. MAO technology is well developed for aluminum alloys. As for titanium alloys, the MAO technology of surface hardening for them requires further research. Goal. In order to improve the mechanical characteristics of titanium alloys it is necessary to establish patterns of influence of regimes and electrolyte composition during MAO process on the phase composition, microhardness and tribological characteristics of coatings obtained by microarc oxidation of VT3-1 and PT-3V titanium alloys. Methodology. X-ray structural analysis (DRON-3) in radiation Кα-Cu, microhardness measurement (PMT-3) with 100 gr load, measurement of coating thickness (vortex thickness gauge BT-10NTs), tribological tests (SMC-2) was used. Results. The MAO treatment of the alloys was carried out in an alkaline electrolyte (KOH) with the addition of sodium aluminate (NaAlO2), sodium hexametophosphate (NaPO3)6 and water glass (Na2SiO3, ρ ≈ 1.4 g/cm3). A metallographic study of the cross section of titanium alloys with MAO coating made it possible to establish that the coating has a two-layer structure consisting of a technological (porous) and main (dense, base) layers. The results of X-ray diffraction analysis showed that the main phases of the coating are the phases TiO2 – rutile, TiO2 – anatase, as well as compounds Al2TiO5 – aluminum titanate. The specific volume of the formed oxides exceeds the volume of the titanium base on which it is formed. So, for TiO2 Voх/Vmet. ≈ 1.8; for Al2TiO5 – 4.4; for mullite – 13.9. This factor contributes to the formation of continuous coatings. It was established that in order to achieve the highest hardness, the presence of the NaAlO2 component in the electrolyte is necessary. This made it possible to achieve a hardness of 11000 MPa of MAO coating on VT3-1 alloy using an electrolyte of 1.75 g/L KOH + 1 g/L Na2SiO3 + 2 g/L NaAlO2. For the PT-3V alloy, the use of an electrolyte of a similar composition can achieve a hardness of 7500 MPa. It is shown that the use of MAO processing of titanium alloys allows to reduce the dry friction coefficient in the VT3-1 – SCh20 system to 0.1. Originality. The structure, phase composition and properties are determined by electrolysis conditions and coating thickness. Practical value. The results obtained are a recommendation for surface hardening of PT-3V and VT3-1 titanium alloys for their further use in friction elements.

β-Ti-based alloys for medical applications

Titanium alloys have been used for medical purposes for over 60 years. They are used in the manufacture of artificial heart valves, stents of blood vessels, endoprostheses of bones and joints (shoulder, knee, hip, elbow), for auricle reconstruction, in facial surgery, and also as dental implants. In first-generation materials (such as commercially pure titanium or VT6 alloys), the matrix consisted of the α-Ti phase or α-Ti and β-Ti mixture. Unfortunately, implants made of first-generation materials require replacement after 10–15 years of usage. This is due to the degradation of implants and loss of contact with the bone. Recently, these materials have been replaced by β-Ti alloys. These second- generation materials make it possible to exclude the harmful effect of aluminum and vanadium ions released during the gradual implant corrosion, and their elastic modulus is closer to the values for living bone than those for α and α+β alloys. Important areas in the development of β-Ti alloys include increasing their mechanical strength, fatigue strength, corrosion resistance and biocompatibility. New methods for the production and thermo-mechanical processing of titanium alloys arise and develop such as additive technologies or severe plastic deformation. Expensive alloying elements (such as tantalum, zirconium or niobium) are quite successfully replaced with cheaper ones (for example, chromium and manganese). As a result, the properties of titanium implants are gradually getting closer to that of the human bone, and their service life is steadily increasing. Therefore, this paper describes a comparative analysis conducted in relation to β-titanium-based alloys for medical applications.

Effect of deformation on α-β phase transformation temperature of a metestable TiZr based alloy

The preparation process of titanium alloys usually includes hot deformation and post heat treatment, and the formulation of heat treatment process needs to be based on the key factor of α-β phase transformation temperature. The results of current study show that the α-β transformation temperature will change obviously after hot deformation. The transformation temperature of α → β phase decreases after deformation in the single α region, and the transformation temperature of β → α phase increases with deformation in the single β region. The key reason is that the energy of α and β phase increases and the phase stability decreases due to the defects formed during hot deforming. The current study means that titanium alloys need to be analyzed by DSC before heat treatment, and the phase transformation temperature should be re-determined according to different deformation processing. The results of current study are of great significance to the formulation of heat treatment process for titanium alloys.

Quantitative analysis on the surface topography of Ti-6Al-4V machined by abrasive suspension jet

Surface topography is the intrinsic determinant of the roughness that is a significant evaluation standard for the machining quality of the abrasive suspension jet (ASJ). To achieve quantitative analysis on the surface topography machined by ASJ, this paper measured the roughness and the scratch size of the cutting surface with an ultra-deep three-dimensional microscope. Ti-6Al-4V (TC4), a typical hard machining material widely used in aviation industry, was chosen as the cutting target. From a macroperspective, the cutting surface is divided into four zones from top to bottom including the initial zone, the smooth zone, the transition zone, and the rough zone. With 1.6-μm set as the standard roughness, the length of the initial zones and the smooth zone were analyzed and determined. From a microperspective, there are a large number of particle scratches with micron scale size laid on the cutting surface. The experimental results showed that the length of the scratches in the initial zone was less than the one in the smooth zone, while it was opposite in the scratch depth and width, and that the initial zone is larger than the smooth zone in surface roughness could be explained. The abrasive particle size is the only influent parameters of the scratch size, and small abrasive particles can be used for reducing the roughness in the initial zone and smooth zone. The conclusions can provide theory guidance for abrasive water jet processing titanium alloys precisely.

Optimization of EDM process of titanium alloy using EPSDE technique

Electrical discharge machining (EDM) is now a widely adopted subtractive manufacturing process to shape titanium and its alloys to obtain desired profile and surface integrity. Predicting and optimizing the process behavior is the need of today’s manufacturing paradigm. Many new and better optimization algorithms have came into existence in the recent past to extract best out of any manufacturing processes. In this paper, EDM has been carried out on Ti–6Al–4 V alloy by varying important electrical parameters to estimate the two of the major performances i.e. material removal rate (MRR) and tool wear rate (TWR). Second-order regression equation using statistical analysis has been obtained for both the performances. Single objective optimization has been done using four evolutionary optimization algorithms. All the four algorithms have been compared for their performances in the present research environment.

Revisiting the lamellar globularization behavior of a two-phase titanium alloy from the perspective of deformation modes

Abstract The correlation between lamellar globularization and deformation modes during the primary hot processing of titanium alloy was evaluated by means of uniaxial compression, tension, torsion and plane strain compression tests. The microstructure evolution features and underlying globularization mechanisms were comparatively studied via Electron Backscattered Diffraction technique. Noticeable divergences of globularization response are captured in different deformation modes, especially for the globularized fractions and the critical strain. In the face of the strain applied is less than the critical globularization value (0.4−0.63) under uniaxial compression, the lamellae can be still globularized under tension or torsion deformation. But the growth rate of globularized fraction is more sluggish under tension than that under torsion deformation. The lamellae separation at early tension deformation preferentially occurs at junctions of lamellae without destroying Burgers Orientation relationship and significant orientation fluctuation. Shear deformation can facilitate the formation of intra-α boundaries and its distribution uniformity, which could make the lamellae grow up into globularized particles and improve the globularization heterogeneity. It is envisaged that the results obtained can provide guidance for the technology scheme and route design of primary hot working of titanium alloy aiming at the homogeneous equiaxed grains.

The effect of laser irradiation of the surface of VT6 titanium alloy on its microstructure, roughness and friction coefficient

The article discusses the technology of laser processing of VT6 titanium alloy as a technological operation to improve properties and structure. A promising direction for reducing roughness during laser hardening with reflow can be the development of a process using additives that reduce the surface tension of the melt and increase the wettability of the surface. It was revealed that phase hardening and martensitic transformation β → α are the causes of hardening of titanium during laser processing. This is confirmed by a change in the width of the x-ray lines. It was found that during laser processing with a speed of 3.7 mm/s and higher, a fine-grained structure is achieved.The results show that, at a sufficiently high cooling rate of the substrate, the grain sizes remain practically unchanged. Russian Federation “The influence of magnetic fields and ion implantation on the electrical structure and properties of titanium, aluminum alloys and elementary semiconductors”

Influence of dynamic angles and cutting strain on chip morphology and cutting forces during titanium alloy Ti-6Al-4 V vibration-assisted drilling

Vibration-assisted machining (VAM) is implemented in titanium alloy processing to solve some challenges, such as difficulty in chip breaking, large cutting forces, and high cutting temperatures. Based on the multi-region dynamic angles and the double-side wedge angle deformation mechanism, this study improves the vibration-assisted drilling (VAD) cutting forces and chip breaking model. The dynamic kinematics angles, the behavior of parameter influence, and the cutting strain effect of intermittent VAM are analyzed. VAD and conventional drilling (CD) experiments are carried out for model validation and mechanism analysis. The experiments show that the maximum deviation of the drilling forces simulation value and the experimental value is 9.13 %. Compared with the CD, the cutting force of the VAD is decreased by 10.1 %–46.2 %. The dynamic feed angle causes multiple cutting angles fluctuations, which affects cutting performance. The adjustment of the VAD cutting parameter value could reduce the chip length by 26.6 %–43.9 %. Material cutting strain presents multi-region characteristic, which influences the chip morphology. This study provides a reference for VAM parameter optimization.

A study on the machinability of advanced arc PVD AlCrN-coated tungsten carbide tools in drilling of CFRP/titanium alloy stacks

This study aims to investigate the effect of an aluminum chromium nitride (AlCrN) coating on tool wear and hole quality in the conventional drilling process of carbon fiber-reinforced plastic (CFRP) composites, titanium alloy (Ti), and CFRP–Ti stack workpieces popular in the aerospace industry. The advanced arc plasma acceleration (APA) method of physical vapor deposition (PVD) was used for all AlCrN coatings. The drilling experiments were conducted with uncoated drills as well as AlCrN-coated drills. When drilling CFRP only, the AlCrN coating was removed at the drill cutting edges and the margin area, which suggests the carbon fibers abraded the coatings. When drilling Ti only, the AlCrN-coated drill mitigated the Ti adhesion formation, which resulted in less tool wear. In addition, hole quality for both CFRP and Ti was improved when the coating was used versus the uncoated tool. The machinability of CFRP–Ti stacks in the drilling process was improved by utilizing the advanced AlCrN coating on the WC tool in terms of drilling forces and hole quality parameters such as average hole size, average hole roundness, hole surface roughness, and Ti exit burr height.

The study on surface grinding process of TI–6AL–4V alloy with resinoid cBN grinding wheel

The grinding process of Titanium (Ti) alloys is extremely difficult as the cutting temperature is much higher than other machining processes due to the low thermal conductivity, high chemical reactivity, and rapid work hardening during machining of Ti alloys. This research investigates the effect of technology parameters on the surface roughness in the surface grinding of Ti–6Al–4V (Ti64) alloy with resinoid cBN grinding wheel. The experimental results show that the surface roughness is significantly affected by the feed rate, depth of cut (DOC) and cooling condition. Increasing feed rate or DOC all provides the higher surface roughness. The surface roughness obtained in the wet grinding is higher than those of the dry cutting. The scanning electron microscopy (SEM) images of Ti64 surfaces show that the machining surface with fewer defects can be produced with wet grinding process.

Microstructure evolution and mechanical properties of wire-feed electron beam additive manufactured Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy with different subtransus heat treatments

Wire-feed electron beam additive manufacturing (EBAM) is a promising manufacturing process for fabrication large-scale, fully dense and near net shape metallic components. However, limited knowledge is available on the wire-feed EBAM process of titanium alloys. In this work, the Ti-5Al-2Sn-2Zr-4Mo-4Cr near β titanium alloy sample was fabricated by the EBAM process and the effect of subtransus solution and aging treatment on the microstructure evolution and mechanical properties was investigated. The results reveal that the volume fraction of the primary α decrease dramatically from 48.6% to 8.9% with increasing the solution temperature from 750 °C to 850 °C. The ultimate tensile strength and yield strength increase monotonously with increasing of the solution temperature, while the elongation and reduction of area change conversely. The thickness of the secondary α (αS) increases significantly from 28.6 nm to 120.1 nm with the aging temperature increasing from 550 °C to 710 °C. The volume fraction and thickness of αS are sensitive to the aging temperature and strongly influence the mechanical properties. The quantitative relationship between the microstructure and mechanical properties was established. As a good result, the tensile properties of the post-deposition heat treated alloy at 400 °C can meet the standard requirements for wrought counterpart.