Processing Of Titanium Alloys Research Articles

Optimization of Cutting Parameters for Sustainable Machining of Titanium Ti-5553 Alloy using Genetic Algorithm

Titanium Ti-5553 alloys have been considered as difficult-to-machine materials due to the extremely high tool wear, high cutting forces, high temperature, and poor surface quality of machined parts. Process parameters needs to be optimized in order to improve machining performance and in the meantime reducing manufacturing cost. This study proposes sustainable machining process for this new generation Titanium Ti-5553 alloy. Process parameters including depth of cut, cutting speed, and feed rate were taken into account to optimize parameters for reducing tool wear, energy consumption, and surface roughness, and in the meantime increase material removal rate. Genetic algorithm was utilized for optimizing the process parameters. Obtained results illustrated that optimization using genetic algorithm is a very effective approach to substantially improve machining performance of this alloy and make machining process of this alloy more sustainable by reducing energy consumption, manufacturing cost and increasing material removal rate in machining process of new generation titanium alloy.

Analysis of the Elevated Temperature Plastic Flow Response of Ti-6Al-4V Produced via the Hydrogen Sintering and Phase Transformation (HSPT) Process

An analysis pertaining to hot deformation behavior was conducted on two unique titanium alloy microstructures. Each product was manufactured from commercially available blended elemental Ti-6Al-4V powder, consolidated by sintering in vacuum or hydrogen. The initial microstructures produced by these distinctive sintering atmospheres are represented by a coarse lamellar structure (produced by vacuum sintering) and a very fine lamellar structure [produced by Hydrogen Sintering Phase Transformation (HSPT)]. Performance of these materials was assessed by simulating representative titanium breakdown and conversion during thermomechanical processing through elevated temperature compression testing on a Gleeble® 3500 Hydrawedge II® system. Compression tests were performed on cylindrical specimens at sub and near-transus temperatures (850 °C, 900 °C, 950 °C, and 1000 °C) and at moderate strain rates of 0.01 and 0.10 s−1. The very fine lamellar microstructure exhibited similar flow behavior compared to the coarse lamellar structure, although with a typically slightly higher peak stress and greater degree of flow softening. In addition, the microstructure produced by HSPT retained a fine, equiaxed structure upon deformation, making it highly suitable for powder-based thermomechanically processed titanium alloy products.

Erosion characteristics of electrical discharge machining using graphene powder in deionized water as dielectric

This paper presented a new electrical discharge machining (EDM) method using powder mixed effects formed by the graphene–water dielectric to improve the machining performance in processing titanium alloy. Theoretical and simulation models were developed to analyze the effects of graphene bubbles on discharge breakdown characteristics and the plasma channel. To validate the theoretical model, single-pulse experiments were conducted by analyzing the shape and dimension of single-discharge craters. Comparative and exploratory experiments were carried out to investigate the erosion characteristics of the new machining approach. Experimental results show that graphene bubbles could affect the erosion characteristics and improve the machinability of titanium alloy. The material removal rate was increased by 28% and surface roughness was reduced by 55%, whereas relative electrode wear was reduced by 43% compared to traditional EDM processes.

Residual stress relaxation and re-shot-peening process of wet shot-peened titanium alloy during tensile fatigue load

Residual stress relaxation and re-shot-peening process of wet shot-peened titanium alloy during tensile fatigue load

Development of a model for the optimization of energy consumption during the milling operation of titanium alloy (Ti6Al4V)

The quest for improvement in the cost effectiveness, environmental friendliness and the energy efficiency during the machining process of titanium alloy has necessitated the use of numerical and physical experimentations for the optimization of energy consumption. The Response Surface Methodology (RSM) was employed for the numerical experimentation with the process parameters in the following range; cutting speed (250–270 mm/min), feed rate (0.05–030 mm) and axial depth of cut (0.50–3.0 mm). The physical experiments were investigated using a DMU80monoBLOCK Deckel Maho 5-axis CNC milling machine with a spindle speed of 1800 rpm. A mill cutter (SF550: HRC 40-HRC 50) was employed for the cutting operation while a KISTLER dynamometer (9257A 8-Channel Summation of Type 5001A Multichannel Amplifier) with the data acquisition system was used for the cutting force measurement. Using the 2FI model, the statistical analysis of the results obtained produced a mathematical model which correlates the process parameters as a function of the specific cutting energy. The results obtained show that the specific cutting energy, cutting speed and depth of cut increases with a decrease in feed rate. The findings of this work will assist manufacturers in the energy optimization and conservation during the machining operation of titanium alloy.

Chemical- and Mechanical-Induced Lubrication Mechanisms during Hot Rolling of Titanium Alloys Using a Mixed Graphene-Incorporating Lubricant.

Hot rolling of titanium alloy currently is carried out without lubrication because of the surface defects. In order to explore an effective lubrication scheme to reduce friction and wear during hot rolling of titanium alloy, a mixed graphene-incorporating lubricant has been proposed to study its lubrication performance and mechanism. The tribological experiments were carried out by ball-disk friction and wear tester under hot-rolling parameters. Scanning electron microscopy (SEM), X-ray energy spectrum analyzer (EDS), X-ray powder diffractometer (XRD) and Raman analysis were used to analyse the surface and cross-section of the wear marks on the samples after the tribological experiments. The results show that the friction coefficient decreases up to about 35% compared with tests under dry and lubricated conditions. The surface quality of the wear marks is improved significantly after applying the proposed lubricant. The graphene which is embedded in the phosphate film can be effectively applied as a lubricating material to strengthen the lubricating film with less combustion loss at high temperatures. A chemical- and mechanical-induced lubrication mechanism for the hot rolling of titanium sheets has been proposed due to the synergistic lubrication effect of the graphene, ZrO2 nano particles and phosphate. It is of great significance and potential value to apply this proposed lubricant as an effective way to reduce the wear, friction and oxidation during the hot-rolling process of titanium alloy.

High temperature creep behavior of hydrogenated Ti-6Al-4V alloy

The thermal creep forming and thermo-hydrogen processing of titanium alloys have been used in industry production. The combination of these methods is a potential way to improve the plasticity of titanium alloys and the formability of complex components. The effect of hydrogen addition on high temperature creep behavior of Ti-6Al-4V alloy was investigated by creep tests and microstructural observations. The results show that β/α phase ratio increases with hydrogen content while α′ and αʺ martensites continuously precipitate in β phase. The α/β or α/α phase boundaries become wider. Hydrogen can promote creep rate through softening effect during primary and steady creep stage. However, the embrittlement happens in the tertiary creep stage. The hydrogenated alloy is more sensitive to initial stress and creep temperature. The creep strain of hydrogenated alloy with 0.2 wt%H is similar to that of as-received one. Meanwhile, the creep strain of hydrogenated alloy with 0.4 wt%H significantly decreases. Besides, the smaller initial stress is beneficial to obtain the larger creep strain.

Treatment of Titanium Alloys Based on Preliminary Plastic Impact

This paper proposed a new method for processing titanium alloys based on preliminary plastic impact. The reasons for the deterioration of the surface roughness of titanium alloys during machining are considered. This problem lies in the formation of outgrowths on tool cutting wedge, which leads to the cutting process taking place as in the titanium-titanium pair. The adsorption phenomenon leads to the fact that the outgrowth is saturated with gases from the environment, and a thick oxide film is formed. As a result, high temperatures arise during machining from 1100 to 1200°C, increasing the cutting forces P and friction Q, which introduce the technological system into an unstable self-oscillating process. The problem posed eliminated by the method of preliminary plastic deformation, which forms a local inhomogeneous structure. At the stage of processing the titanium billet, the cutting edge enters the region with a heterogeneous structure, destroying the chips and growth with an oxide film. Since most of the temperature, about 80% takes away with the chips, the amplitude of the self-oscillating process decreases, which reduces the surface roughness of the processed titanium alloys.

An Experimental Study on Milling Titanium Alloy with a Revolving Cycloid Milling Cutter

In this paper, a revolving cycloid milling cutter was designed with a larger effective cutting helix angle and rake angle than a ball end milling cutter of the same diameter. This new type of milling cutter can solve the problems of low machining efficiency, severe tool wear, and low surface quality in titanium alloy processing. A comparison of the cutting performance of titanium alloys processed by the revolving cycloid milling cutter and the ball end milling cutter was carried out to obtain the variation laws of the cutting force and the processing surface quality under different tool wear conditions. The result shows that the wear zone of the revolving cycloid milling cutter is shallow and wide compared to that of the ball end milling cutter. As the wear speeds up, the spoon-shaped wear gathering zone found in the ball end milling cutter does not happen with the revolving cycloid milling cutter. The revolving cycloid milling cutter can significantly lower the axial force, the tangential force, and the ratio of the axial force to the tangential force with a stable cutting process.

Establishment of micropit diameter prediction models based on the support vector machine optimization

Many studies on microtextures have focused on the effect of laser processing parameters on microtextured morphology from the experimental point of view, and not on its influence on the physical field and stress field around the microtextures. This has resulted in the lack of accurate predictions on micropit diameters, thus reducing the processing efficiency. In order to address these problems, the effects of laser processing parameters on the precision machining, physical field, and stress field of micropit textures for a ball-end milling cutter were studied by experiments and simulation. The optimum laser processing parameters include laser power of 70%, scanning speed of 1700 mm/s, and scanning of seven times. Based on the optimized data of a support vector machine, the prediction models of micropit diameters for laser machining were established. The errors of the models are less than 10%, thus verifying their accuracy. This study can serve as a theoretical reference for the efficient processing of titanium alloys.

Effects of different tool microstructures on the precision turning of titanium alloy TC21

Titanium alloys are widely used in the aviation field due to the excellent properties, such as high specific-strength and high-temperature resistance. But the poor machinability of titanium alloys has brought the great difficulty to its machining process. In the cutting process of titanium alloys, tool wear is very serious, and the machining quality is difficult to be guaranteed. As a new type titanium alloy, TC21 alloy has the higher strength and its machinability is less than other titanium alloys. Aiming at the cutting defects in the cutting process of TC21 alloy, three different microstructures, including parallel, perpendicular and wavy grooves, are presented and cut on the rake surface of tools by the laser texturing method. A series of precision turning process of TC21 alloy are implemented on the precision machine using the inserts with different microstructures. The effects of the different microstructures on the chip morphology, turning force, surface morphology, and surface roughness are investigated deeply. The results demonstrates that the tool microstructures have very important role on the turning process of titanium alloys and the wavy microstructure has the best effect in improving the machinability of titanium alloy TC21.

Microstructure/texture evolution maps to optimize hot deformation process of near-α titanium alloy

The microstructure/texture evolution (MTE, for short) map and processing map of a new near α titanium alloy Ti65 were constructed in order to investigate the workability and microstructure evolution of hot deformation. The processing map illustrated four domains, two summit domains and two instability domains. The morphologies of the α phase changed from the spheroidization (α+β region) to the deformed and elongated β grains (near the β transus temperature Tβ), and then to the obvious dynamic recrystallization (DRX) (β region) with the temperature rising from 930 °C to 1140 °C. Deformation in the α+β field mainly generated the texture component with [0001] or [022‾3] parallel to radial directions (RDs). While deformation in the β phase field formed two types of texture component with [0001] parallel to RDs and [21‾1‾0] parallel to compression direction. An optimized processing map was summarized by overlaying the macro-instability map on the original processing map, and the instability domain of Ti65 alloy was confirmed in the area with the strain rate higher than 0.01 s−1.

Effects of Cooling Rate on the Microstructure and Tensile Properties of Wire-Arc Additive Manufactured Ti–6Al–4V Alloy

Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing process of titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting is strong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructure and tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperature control. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness properties were also improved.

Interface characteristics in an α+β titanium alloy

The alpha/beta interface in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) is investigated via centre of symmetry analysis, both as-grown and after 10% cold work. Semi-coherent interface steps are observed at a spacing of 4.5 +/-1.13 atoms in the as-grown condition, in good agreement with theory prediction (4.37 atoms). Lattice accommodation is observed, with elongation along [-1 2 -1 0]alpha and contraction along [1 0 -1 0]alpha . Deformed alpha exhibited larger, less coherent steps with slip bands lying in {110}beta. This indicates dislocation pile-up at the grain boundary, a precursor to globularisation, offering insight into the effect of deformation processing on the interface, which is important for titanium alloy processing route design.

Post-dynamic α to β phase transformation and reverse transformation of Ti-5Al-3V alloy after hot deformation in two phase region

The microstructural evolutions and resulted mechanical responses during isothermal holding of multipass hot deformation are essential aspects in the processing of high performance titanium alloys. In this work, isothermal holding testing was performed on a Ti-5Al-3V alloy after hot compression at temperatures of 900 °C, 930 °C and 960 °C, respectively. Stress relaxation, dilatometer measurements, and microstructure examinations (i.e. scanning electron microscope, electron backscatter diffraction and transmission electron microscope) were employed to investigate the phase transformation behaviors. The results showed a flow stress hardening phenomenon during the interrupted isothermal holding in two phase region. The post-dynamic transformation from α to β phase took place first during the early stage of isothermal holding after hot deformation. With longer isothermal holding time, the reverse transformation of meta-stable β phase to α phase was then observed. Under TEM, the reverse transformed α phases were isolated from quenched α' phases. The in-depth mechanisms of post-dynamic α to β phase transformation and reverse transformation were discussed as well.

Experimental analysis of the EDM process of dissimilar materials

The aim of the present study is to investigate the surface roughness of Electrical Discharged Machined (EDM) samples with Electrode Tool (ET) materials. For the experiments, three different types of ETs were considered which are made of different materials viz. composite, copper, and graphite. Aluminium, low alloy 35GS steel and OT4 titanium alloy were selected as the workpiece materials. Machining parameters used were: current (I) 8 A, voltage (U) 100 V, and pulse duration (Ton) as 150 μs. It was found that the ET made of composite material performs best in EDM of 35GS steel and OT4 titanium alloy. Specifically it was concluded that in the first case, the performance of composite ET is higher than graphite ET by 59 %. Similarly, in the second case, its productivity was found to be 74% and 95% higher when machined with graphite and copper ET respectively. Moreover, the surface roughness values of 35GS steel machined with composite ET was found to be 15% higher when machined with copper and graphite ET. While processing titanium alloy with composite ET, surface roughness values were observed as high as 44% and 25% when machined with copper and graphite ET respectively.

Peculiarities of wear of nanostructured topocomposites on the hard-alloy basis

The article considers the wear resistance and wear peculiarities of nanostructured topocomposites with the clustered gradient architecture. The authors regard the specificity of the impact of the cluster morphology on the contact interaction under microcutting conditions. They study the causes of persistence of the high wear resistance for the given class of nanostructured topocomposites. The mechanisms of energy dissipation from the tribocontact zone due to their nanogeometry and the structural-phase structure are analyzed. The contribution of triboactivated diffusion and deformation processes to providing the increased wear resistance of topocomposites on the hard-alloy basis is differentiated. Their approbation in the conditions of edge cutting processing of heat-resistant titanium alloy is carried out.

Thermomechanical Processing of Titanium and Nickel Alloys

This article considers aspects of thermomechanical processing at T > 400°C of Ti and Ni alloys with shape memory and the properties of materials with thermal elastic transformations, depending on the thermal and thermomechanical action as well as the aspects of thermal processing of metals with thermoelastic transformations. Technologies are proposed for applying thermal processing to alloy parts with shape memory, depending on preliminary processing and the kind of workpiece (half-finished products).

Effect of cluster-gradient architecture of nanostructured topocomposites on features of tribointeraction with heterophased material

The wear resistance and wear characteristics of cluster-gradient architecture (CGA) nanostructured topocomposites are studied. The specifics of tribocontact interaction under microcutting conditions is considered. The reasons for retention of high wear resistance of this class of nanostructured topocomposites are studied. The mechanisms of energy dissipation from the tribocontact zone, due to the nanogeometry and the structural-phase structure of CGA topocomposites are analyzed. The role of triboactivated deformation and diffusion processes in providing increased wear resistance of carbide-based topocomposites is shown. They are tested under the conditions of blade processing of heat-resistant titanium alloy.

Research on Underwater Laser Welding with Filler Wire Process of TC4 Titanium Alloy

Research on Underwater Laser Welding with Filler Wire Process of TC4 Titanium Alloy