Titanium and nickel alloys are used in the creation of components exposed to harsh and variable operating conditions. Such components include thin-walled structures with a variety of shapes created ...using milling. The driving factors behind the use of thin-walled components include the desire to reduce the weight of the structures and reduce the costs, which can sometimes be achieved by reducing the machining time. This situation necessitates, among other things, the use of new machining methods and/or better machining parameters. The available tools, geometrically designed for different strategies, allow working with similar and improved cutting parameters (increased cutting speeds or higher feed rates) without jeopardizing the necessary quality of finished products. This approach causes undesirable phenomena, such as the appearance of vibrations during machining, which adversely affect the surface quality including the surface roughness. A search is underway for cutting parameters that will minimize the vibration while meeting the quality requirements. Therefore, researching and evaluating the impact of cutting conditions are justified and common in scientific studies. In our work, we have focused on the quality characteristics of horizontal thin-walled structures from Tisub.6Alsub.4V titanium alloys obtained in the milling process. Our experiments were conducted under controlled cutting conditions at a constant value of the material removal rate (2.03 cmsup.3⁄min), while an increased value of the cut layer was used and tested for use in finishing machining. We used three different cutting tools, namely, one for general purpose machining, one for high-performance machining, and one for high-speed machining. Two strategies were adopted: adaptive face milling and adaptive cylindrical milling. The output quantities included the results of acceleration vibration amplitudes, and selected surface topography parameters of waviness (Wsub.a and Wsub.z) and roughness (Rsub.a and Rsub.z). The lowest values of the pertinent quantities were found for a sample machined with a high-performance tool using adaptive face milling. Surfaces typical of chatter vibrations were seen for all samples.
As a dielectric, biolubricant (vegetable oil) cannot maximize the efficiency of electrostatic atomization minimum quantity lubrication (EMQL). The lecithin-enhanced technology is expected to solve ...this technical bottleneck. The effects of lecithin on the electrophysiological properties of biolubricant (soybean oil) were investigated. Lecithin can increase the conductivity, viscosity, and charge mass ratio and reduce the surface tension of soybean oil. Comparative experiments show that the maximum average temperature rise of workpiece surface with MQL is 241.6 °C. The value under flooding, EMQL, and L+EMQL is reduced by 28.97%, 42.8%, and 48.92%, respectively, compared with MQL. The influence of lecithin mixing ratio on grinding performance was discussed. The minimum surface roughness value (0.49 µm) is obtained at the mixing ratio of 2:10.
•A new grinding method of lecithin bioubricant EMQL was proposed.•The effects of lecithin addition on physical characteristics of vegetable oil were studied.•Several groups of comparative experiments are carried out to verify the effectiveness of L+EMQL lubrication method.•L+EMQL method can reduce the grinding temperature and improve the surface quality of workpiece effectively.•Lecithin has self-assembly behavior in non-polar oil, which can improve its lubrication performance effectively.
Titanium is a good example of a material that is globally recognized for its outstanding properties, making it desirable for a range of industries. Titanium and its alloys are utilized in a wide ...range of industries, including aerospace, automotive and high performance leisure equipment. This Special Issue of Metals focusing on titanium contains a range of articles based on research into this fascinating material and its wide range of alloys. For applications that can withstand the high basic cost of titanium it is shown that the unique properties of the material have the potential to provide further performance improvements to existing industries, whilst offering new opportunities to emerging markets.
Duplex aging is one of the common heat treatments in titanium alloys. The microstructure introduced in the first-step aging has an effect on the growth/dissolution of alpha in the second-step aging. ...In the present work, a beta + alpha.sub.acicular microstructure is preset in Ti-55531 (Ti-5Al-5Mo-5V-3Cr-1Zr wt%) alloy. The isochronal and isothermal phase transformation kinetics in the second-step aging is studied by combining the dilatometer test with microstructure characterization and local composition mapping. The phase transformations and corresponding temperature ranges are determined as beta right arrow alpha.sub.acicular 643-845 K and alpha.sub.acicular right arrow beta 845-1130 K by isochronal annealing. A TTT diagram for isothermal transformation kinetics is plotted based on the transformed phase fraction and reproduced by Johnson-Mehl-Avrami theory. The calculated kinetic curves are in good agreement with experiment ones. The C-shaped TTT curves verify the classical nucleation and growth of alpha in the second-step aging. In comparison with Ti-55531 alloy with preset beta + alpha.sub.lath microstructure (in authors' previous work), the alpha precipitation exhibits prolonged incubation period and slowed average transformation rate, which is evidenced by a right shift of C-curves for the alpha precipitation portion along the time axis. However, the C-curves of alpha dissolution show a left shift on the TTT diagram. The precipitation kinetics of alpha aciculae from dilatometry is synchronous with that obtained from the diffusion of Al detected in STEM mapping, while the diffusion of slow-diffusion elements lags behind the structural transformation. The TTT diagram and the dataset of microstructure features obtained in the present work can be employed to optimize processing in duplex aging.
Titanium (Ti) alloys, which are highly promising as structural materials in critical industrial applications, generally require high strength and ductility, particularly high fracture toughness. ...However, the conventional approach of enhancing strength through mechanical processing to induce dislocations often leads to a compromised ductility known as the strength-ductility trade-off. Here, we develop a new strategy of the nanocrystallized kinks to overcome this issue in Ti-11V metastable β-Ti alloys via combining industrially used cold forging (CF) and cold rolling (CR) processes. Deformation kinks are firstly activated by CF, and subsequently they are fragmented into nanograins during CR, architecting nanocrystallized kinks in the coarse-grained matrix. This unique microstructure effectively balances the strength-ductility conflict, endowing this Ti-V binary alloy with high yield strength ∼1200 MPa, appreciable ductility ∼17 % and high fracture toughness ∼ 52.0 MPa·m½, which is superior to numerous multielement engineering Ti alloys. This design strategy of nanocrystallized kinks can be extended to other engineering materials, e.g., Mg and Zr alloys, for advanced performance at large industrial scales.
Display omitted
β-Titanium alloys demonstrate unique properties, especially their low elastic modulus, good balance of strength and ductility, and strong heat treatment response. In this study, pre-alloyed powder of ...a β-Ti-alloy Ti–34Nb–13Ta–5Zr-0.3O (TNTZO) was processed using Laser Powder Bed Fusion (LPBF). Dense builds that demonstrate a full β microstructure with limited texture were achieved following process optimisation, with an elastic modulus of 56.5 GPa, tensile strength of 756 MPa, elongation-to-failure of 20 %, and recoverable strain of 1.3 %. Due to the high oxygen content, the β→α′′ deformation induced transformation was supressed, which resulted in a typical elastic-plastic stress-strain behaviour unlike the double-yielding behaviour typically experienced in superelastic Ti-alloys. The alloy was particularly sensitive to ageing heat treatments that resulted in needle α-precipitation, with tensile strengths exceeding 950 MPa, elastic modulus of ∼80 GPa, and recoverable strain of 1.5 %, yet at the expense of a reduced elongation-to-failure of 9 %. Transmission electron microscopy and electron backscattered diffraction investigations revealed the deformation mechanism was slip-dominated with no trace of twinning or stress induced phase transformation.
Display omitted
Taking advantage of high strength of a titanium alloy and high ductility of the other one is performed to manufacture titanium laminated composite that is promisingly applied in high strain rate ...environments, but the challenge of fabricating high bonding interface of the two titanium alloys still needs to be overcome. In this work, the TB9/TC4 titanium laminated composite was successfully prepared by hot rolling. A strong bonding interface was constructed between the layers of TB9 and TC4 titanium alloys, achieving a high shear strength of up to 770 MPa. The dynamic compression of the TB9/TC4 titanium laminated composite under Split Hopkinson Pressure Bar (SHPB) showed that the stress-strain curve of the composite presented a unique dual-peak feature, indicative of an excellent strain hardening capability. The TB9/TC4 interface, characterized by coherent and low interface formation energy, facilitated deformation accommodation between TC4 and TB9 layers. Concurrently, the TB9/TC4 interface hindered the ASBs and triggered dislocation strengthening due to stress concentration, leading to high dynamic strength of the laminated composite.
The aim of the present study is to elucidate the strain rate (ε˙) dependency of Ti–6Al–4V alloys under cryogenic deformation conditions, inspired by our recent observations of strain rate ...insensitivity in pure titanium as well as the temperature effect on the stacking fault energy. Unlike the pronounced strain rate sensitivity at ambient temperatures, a strain rate insensitivity when ε˙ < 10−2 s−1 and strain rate sensitivity when ε˙ > 10−2 s−1 were observed during cryogenic deformation. Subsequent analyses underscored the pivotal role of stacking faults in modulating the transition from strain rate insensitivity to sensitivity with increasing strain rates. The present study therefore enriches the existing knowledge on the mechanism of cryogenic deformation, offering guidance for the engineering of high-performance titanium alloys.
The article discusses the properties and features of heat-resistant titanium alloys. The microstructure of a new titanium alloy VT41, its mechanical and service properties after various processing ...modes are presented. The main problems in the machining of difficult-to-machine titanium alloys are considered. The developed mathematical model of the formation of errors in turning titanium alloys, taking into account thermal deformations and dimensional wear of the cutting tool, elastic deformations of the technological system, is described. The paper presents the results of experimental research on turning of heat-resistant titanium alloy VT41 on a multi-parameter stand.
