Microstructure Of Titanium Alloy Research Articles

Investigation on generation and features of burn defect in Ti6Al4V milling

Owing to the low thermal conductivity and elasticity, cutting burn defect is easy to produce in machining titanium alloy Ti6Al4V. Since the excessive cutting temperature caused by tool wear is the key factor for cutting burn, the relationship between the tool wear rate and cutting burn was studied. In this research, the dynamic process of cutting burn was investigated through wear experiments of cutting tool. The relationship between the tool wear and cutting burn defect were also studied. Then, the microhardness of workpiece was evaluated to analyze the unfavorable effect when the burn defect is occurred. Finally, the microstructure of titanium alloys was observed by scanning electron microscope (SEM) in the dynamic process of burn defect. The α phase particles are coarsened and the mechanical properties of materials are degenerated.

Effect of α and β Phase Volume Fraction on Machining Characteristics of Titanium Alloy Ti6Al4V

Microstructure of titanium alloys has great influence on the manufacturing processes. In the current investigation the effect of change in volume fraction of alpha and transformed beta phase in the bimodal titanium alloy Ti6Al4V was discussed in relation with the mechanical and machining performance. The quenching process in STA (solution treatment and annealing) heat treatment was delayed by 30, 50 and 70 sec to get different microstructural morphology in each heat treated specimen. Face turning experiments with dry and high pressure coolant environment were performed on the solution treated samples. A detailed chip mechanism and microstructural analysis was performed to investigate the role of quench delay and subsequent change in phase volume fraction on thermal softening and frictional phenomenon in machining. The specimen treated with quench delay of 50 sec exhibited poor machinability because of thermal and frictional shock generated at the cutting zone.

Finite Element Modeling and Simulation towards Metallic Microstructure of Titanium Alloy Based on Abaqus

In this paper a new kind of finite element analysis model towards metallic microstructure of titanium alloy is established based on a common metallic microstructure picture. By the simulation of tensile test on this new kind of FEA model performed by finite element analysis software Abaqus, the tensile curve in the state of simulation is obtained. Meanwhile, in order to verify the accuracy of the simulation results, a series of tensile tests are designed and performed and the tensile curves under experimental conditions are obtained. Comparing the experimental results with the simulation results, the conclusion can be verified that the new microstructure FEA model can illustrate the metallic microstructure very well. And this model provides a new perspective to study the mechanical properties of metallic materials.

Effect of Heat Treatment in the Structure and Microstructure of Ti-15Zr-XMo Alloys

Titanium alloys present favorable properties to industry applications that depend on their composition and microstructure. Adding alloy elements and thermomechanical treatments can change the microstructure of titanium alloys. In this paper, Ti-15Zr alloys with different molybdenum quantities were prepared and hot-rolled, having been previously subjected to homogenizing heat treatment. The results showed that the microstructure of the alloys was sensible to heat treatment, in accordance with the theoretical prediction from the molecular orbital method.

W031007 3D積層造形チタン合金の疲労特性と表面改質によるその特性改善の試み

There is a technique for 3D manufacturing the implant in the near-net-shape. To do this, we use a patient's CT image. It is a manufacturing technology by powder additive fabrication using a laser or electron beam. Additive fabrication the titanium alloy microstructure, different from that of the forged material. And, there are many defects. These defects become the origin of fatigue fracture. To use the Additive fabrication titanium alloys, fatigue properties are important. In this study, we have to evaluate the fatigue properties of titanium alloy that was shaped by an electron beam melting method. In addition, it was subjected to a surface modification for the purpose of improving the fatigue characteristics. Specifically, it was fine peening. And, the fatigue characteristics were evaluated and examined its effectiveness.

Attenuation Characteristics of Ultrasonic Velocity and Acoustic-Based TC4 Alloy Uniformity Nondestructive Evaluation

ultrasound characteristics of the material microstructure nondestructive evaluation of its experimental sample TC4 titanium alloy microstructure of two-phase microstructure:. Α-phase and α + β phase. Phase material microstructure and grain area ratio directly affects the material uniformity, uniformity of material differences caused by different grain characteristics which ultrasound parameters. Flooding experiments using ultrasonic method for measuring the material longitudinal wave velocity; measuring the sound attenuation coefficient, combined with the area ratio of the sample α using multiple pulse method. Associated with the sample area ratio between the speed of sound and sound attenuation analysis of α-phase titanium alloy TC4 through the material properties of ultrasound to characterize the degree of uniformity of the material microstructure, nondestructive evaluation of materials in order to achieve the purpose of the microstructure.

Integrated Computational Materials Engineering of Titanium: Current Capabilities Being Developed Under the Metals Affordability Initiative

A technical review of the titanium model development programs currently funded under the Metals Affordability Initiative is presented. Progress of the “Advanced Titanium Alloy Microstructure and Mechanical Property Modeling” and “ICME of Microtexture Evolution and its Effect on Cold Dwell/High/Low Cycle Fatigue Behavior of Dual Phase Titanium Alloys” will be reviewed followed by a discussion of the future modeling needs of the aerospace industry.

On the Texture Formation of Selective Laser Melted Ti-6Al-4V

Selective laser melting (SLM) has been shown to be an attractive manufacturing route for the production of α/β titanium alloys. The relationship between the SLM process parameters and the microstructure of titanium alloys has been the object of several works, but the texture formation during the SLM process has yet to be understood. In the present study, the texture formation of Ti-6Al-4V components was investigated in order to clarify which microstructural features can be tailored during the SLM process. The microstructural characterization of the as-built components was carried out using various microscopy techniques. Phase and texture analysis were carried out using backscattered electron imaging and diffraction. It was found that as-built components consist exclusively of α′ martensitic phase precipitated from prior β columnar grains. The texture of the prior β phase was reconstructed and discussed in relation to the used SLM process parameters. It was found that the β grain solidification is influenced by the laser scan strategy and that the β phase has a strong 〈100〉 texture along its grain growth direction. The α′ martensitic laths that originate from the parent β grains precipitate according to the Burgers orientation relationship. It was observed that α′ laths clusters from the same β grain have a specific misorientation that minimizes the local shape strain. Texture inheritance across successive deposited layers was also observed and discussed in relation to various variant selection mechanisms.

Cyclic plasticity experiments and polycrystal plasticity modeling of three distinct Ti alloy microstructures

Cyclic deformation experiments have been performed on three titanium alloy microstructures to facilitate calibration of two distinct simplified polycrystal plasticity model frameworks. These microstructures include Ti–6Al–4V β-annealed, Ti-18 in a solution-treated, age-hardened (STA) condition (Fanning, 2011), and Ti-18 with a beta-annealed, slow-cooled, age-hardened (BASCA) treatment. Experimental results suggest that superior uniaxial yield strength, ultimate strength and tensile ductility are achieved through the STA processing for the Ti-18 material. This processing route produces a fine bi-modal microstructure. In contrast, corresponding measured properties of the Widmanstätten morphology generated via the BASCA heat treatment were lower. The constitutive frameworks for the two different simplified polycrystal plasticity models and associated flow rules have been outlined and the model parameters have been estimated for cyclic loading such that the simulated stress–strain response is consistent with experimental results for each of the titanium microstructures investigated. In view of envisioned application to fatigue, focus is placed on cyclic behavior after the initial loading cycle(s). Certain estimated parameters differ for each model among microstructures, mainly related to elasticity, threshold for slip system yielding, and work hardening; this suggests limits on a simplified model framework and the need for in situ studies of dislocation-interface reactions and the relative role of β-phase fraction.

A new method for separating complex touching equiaxed and lamellar alpha phases in microstructure of titanium alloy

A new method for separating complex touching equiaxed and lamellar alpha phases in the optical micrograph of titanium alloy was proposed for quantitative characterization. This new method involves three steps. First, concave points of the microstructural feature are identified with a threshold of the concaveness of the corner points which are extracted from the binarized image. Secondly, concave points pairs are selected from the concave points group established by means of marker circle or distance. Third, whether a candidate separation line which connects two concave points within a pair can be accepted or not is determined by the proposed four rules. The obtained results show that this method is effective on separating complex touching microstructural features.

Metallurgical failure analysis of acetabular metal-backed screws

Screws are often used in total hip arthroplasty to increase the cementless acetabular metal-backed fixation stability. This study aimed at identifying metallurgical factors related to metal-backed screw fractures in two cases of premature total hip arthroplasty revision. A preliminary analysis of radiographs and retrieved parts was performed. Fractured screws were subjected to fracture analysis, energy dispersive X-ray spectroscopy (EDS) and metallographic analysis. A finite element analysis was performed to predict the stresses experienced by the screws. Two factors were identified: titanium alloy microstructure, consisting of alpha phase plates with oxygen-rich alpha case and as cast Cr–Co alloy with dendritic microstructure and unfavorably aligned shrinkage formation. Finite element analysis has showed enough level of stress to predict screw fracture in the case of unbounded metal-backed and bone interface.

Effect of Sintering Conditions on Mechanical Properties and Microstructure of Titanium Alloy Produced by Metal Injection Moulding (MIM)

Metal Injection Moulding (MIM) is an efficient method for high volume production of complex shape components from powders. The purpose of this study is to determine the sintering condition of titanium alloy (Ti6Al4V) tensile shape sample. In high temperature, Ti6Al4V will react with oxygen to form of titanium oxide (TiO2) which present a problem during sintering thus affected the mechanical properties and microstructure. This reaction can be avoided either by introducing argon gases or in vacuum condition. Ti6Al4V with binder formulation consist of polyethylene (PE), paraffin wax (PW), stearic acid (SA) and palm oil derivatives; palm stearin (PS) were mixed homogenously and injected to produce green compact. The binders then are removed and sintered at 1100 °C for 8 h. During sintering, the debound part is heated, thus allowing densification of the powder into a dense solid with the elimination of pores. It was expected that the impurity gas in argon had strong effects on aspects of the densification and properties. Samples of PE/PS formulation with argon added to the sintering atmosphere, experience density of 4.375g/cm3 and tensile strength stated at 1000.100MPa compared to samples in vacuum condition which do not show any significant increment with density of 3.943g/cm3 and tensile strength at 325.976MPa. PE/PW/SA samples of vacuum condition also show no improvement in sintered properties. However with additional argon flow the density can reach until 4.359g /cm3 and 940.823MPa of tensile strength. Ti-alloy sintered in argon exhibited better densification rate than in vacuum with high strength, better elongation and lower porosity. In argon, the powder particles became interconnected signifying densification was achieved due of non-reactive properties of inert gases that prevent undesirable chemical reactions from taking place.

Accelerating cyclic plasticity simulations using an adaptive wavelet transformation based multitime scaling method

SUMMARYCyclic finite element simulations of complex materials, for example, polycrystalline metals, are widely used to study fatigue failure due to plasticity and damage. Typically, this requires the simulation of a large number of cycles to failure for accurate determination of evolving deformation variables. Modeling cyclic deformation using conventional methods of time integration in semidiscretization techniques can however be computationally challenging. Single time scale integration methods typically follow the high frequency characteristics and discretize each cycle into a number of time steps over which integration is performed. To overcome this computational challenge, the wavelet transformation‐based multitime scale (WATMUS) method proposed in an earlier work by the authors is advanced and validated in this paper to perform accelerated finite element simulations of materials undergoing rate‐dependent plasticity for large number of cycles. Specifically, the WATMUS algorithm is integrated with crystal plasticity finite element method to perform accelerated simulations of polycrystalline alloys. The WATMUS methodology is also endowed with adaptive capabilities to optimally construct the wavelet basis functions and determine coarse‐scale cycle steps. Accuracy and efficiency of the WATMUS methodology is conclusively demonstrated by comparing the results with cyclic single‐time scale crystal plasticity finite element simulations performed on image‐based microstructure of titanium alloys. Copyright © 2012 John Wiley & Sons, Ltd.

Fabrication of bulk ultrafine grained titanium alloy via equal channel angular pressing based thermomechanical treatment

Equal channel angular pressing (ECAP) is one of the most feasible severe plastic deformation (SPD) techniques for fabrication of bulk ultrafine grained or even nanostructured materials. Previous studies show that the microstructure of titanium alloy (Ti-alloy) subjected to ECAP processing can only be refined to micron-scaled (1–5μm), rather than nano-scaled. In this paper, the ECAP based thermomechanical treatment was successfully conducted for fabrication of bulk ultrafine grained and nanostructured Ti-alloy. In detail, a near α titanium alloy was firstly processed by ECAP at the temperature above α–β transformation temperature (Tβ) and then followed by immediate quenching. The alloy was further pressed at the temperature of α+β phase region (below Tβ). Through observation and analysis of the microstructure evolution, it is found that the ultrafine grained Ti-alloy with partly equiaxed nano-scaled microstructure was successfully produced by the thermomechanical treatment process. To have an in-depth understanding of the process, the microstructure evolution in this grain refinement process and the property improvement after the refinement were extensively examined and discussed.

Changes of microstructure in titanium alloy during high temperature hydrogen treatment

The paper regarding the HTM - Hydrogen Treatment of Materials as an attractive method for controlling microstructure and improving final mechanical properties of titanium alloys. A new variant of high-temperature hydrogen treatment that includes cyclic heat treatment is proposed. This paper present the qualitative description of the microstructure in Ti-6Al-4V alloy after high-temperature hydrogen treatment with cyclic heat treatment operation. Hydrogen treatment consists of the three stages: hydrogenation in hydrogen gas atmosphere (600°C), cyclic heat hydrogen treatment (580°C), dehydrogenation in vacuum (550°C). The possibilities of hydrogen treatment for controlling microstructure layer of titanium alloy was presented.

On the correlation between the morphology of α and its crystallographic orientation relationship with TiB and β in boron-containing Ti–5Al–5Mo–5V–3Cr–0.5Fe alloy

While the role of borides on the microstructure of titanium alloys has been discussed in many previous reports, this paper presents the first experimental evidence of (i) the three-dimensional geometry of α precipitates confirming their equiaxed morphology, as determined by reconstruction of serially sectioned scanning electron microscopy images; and (i) the influence of the crystallographic orientation relationship between β, TiB and α phases on the morphology of α precipitates, investigated via detailed orientation microscopy studies on a boron-containing version of the commercial Ti–5Al–5Mo–5V–3Cr–0.5Fe alloy Ti5553.

Effect of the microstructure of titanium alloys on the fatigue strength characteristics

The fatigue test results and the mechanical characteristics in static tension are obtained for specimens of titanium alloys belonging to the known classes of materials with a reference globular or bimodal microstructure and the so-called fine-grained β-transformed microstructure provided by the rapid heat treatment technique. The microstructure of the materials under study is analyzed. The microstructural parameters responsible for the fatigue strength of particular material have been found. The comparison is made between the fatigue limits obtained experimentally and calculated using the models previously developed by one of the authors.

SEM in situ study on the mechanical behaviour of SiC f/Ti composite subjected to axial tensile load

Ti–6Al–4V matrix composites reinforced by SiC fibers with and without carbon coating (SiC f/Ti–6Al–4V) were prepared by Foil–Fiber–Foil (FFF) method and subjected to heat treatment at 900 °C for 50 h. Subsequently in situ Scanning Electron Microscopy (SEM) technique was used to study fracture mechanism of the composites under axial tensile loads. The influence of fiber coating, interfacial reaction zone and titanium alloy microstructure on initiation and propagation of cracks was investigated in detail. The results show that upon loading, the non coated fibers crack and fracture into smaller fragments. However, the carbon coated fiber does not develop any fracture during the entire experiment and a part of the fiber is pulled out during the final fracture.

Microstructure engineering of materials

Microstructure of most technical alloys for an engineering application would involve multiple phases that could differ in their physical properties, configuration, morphology, size, volume fraction etc. While the choice of a material for a specific application could involve relevant functional property, often a secondary property (such as freezing range, toughness, corrosion or creep resistance, biological compatibility etc.) could play an overwhelming role in the successful usage of that material. Designing the microstructure, taking the material and processing constraints into account, is one of the major areas of materials research today. In the recent past, several novel processing techniques have emerged that have aimed at obtaining a specific microstructure of the material with an intended application. Severe plastic deformation, electromagnetic processing of melts, multi-step thermo-mechanical processing, rapid solidification are some examples of emerging techniques where research is focused on both the materials as well as the processing technique to obtain the designed microstructure. Kinetic constraints such as rate of deformation and rate of cooling imposed during the processing have an important role in the evolution of microstructure. Several new characterization techniques and tools such as orientation imaging, focused ion beam milling and analytical electron microscopy have aided in assessing the efficacy of the engineering approach taken in the design of a microstructure. Advances in the computational modeling of the processing techniques and simulation of microstructure have opened new avenues in the microstructure engineering. In this thematic volume, we present a collection of five papers that bring out the microstructure engineering in the current state of the art. Arvind Kumar, Miha Zaloznik and Herve Combeau have presented their work on prediction of equiaxed grain structure and macrosegregation in an industrial steel ingot and have compared their results with experiments. Sumantra Mandal, V. Subramanya Sarma and A. K. Bhadhuri have performed grain boundary engineering in alloy D9 through thermo-mechanical processing and have studied influence of process variables and delved on the aspects of micro-mechanisms in depth. Georg J. Schmitz, Bernd Bottger, Jain Eiken, Markus Apel, Antoine Carre, Alexandre Viardin and Gottfried Laschet have reviewed the current status of the phase-field based simulations of microstructure evolution in technical grade alloys. Bikramjit Basu and Garima Tripathi have presented their work on processing and biological evaluation of porous hydroxyapatite/poly methyl methacrylate hybrid composites. Seshacharyulu Tamirisakandala and Dan Miracle have reviewed the efforts to engineer the microstructure of titanium alloys using small additions of boron as alloying element. The materials covered in these studies are of current interest for the industry and the processes chosen are of high impact. This thematic issue has a fine balance of experimental and computational studies on the topic. Articles in this theme were contributed by researchers whose groups have contributed significantly to this area for last several years. We hope that readers will find this issue valuable and informative on the theme of microstructure engineering of materials. The ubiquitous presence of microstructure characterization tools in academic departments of varied engineering disciplines indicates that slowly and steadily, the mesoscale information of materials is being studied and engineered for desired performance. B. S. Murty G. Phanikumar (&) Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India e-mail: gphani@iitm.ac.in

Titanium alloy production technology, market prospects and industry development

Titanium alloy with a low density, high specific strength, corrosion resistance and good process performance, is the ideal structural materials for the aerospace engineering. Based on the microstructure of titanium alloys, it can be divided into α-type titanium alloys (heat-resistant titanium alloys), β-type titanium alloys and α + β-type titanium alloys. The research scopes also include the fabrication technology of titanium alloys, powder metallurgy, rapid solidification technology, and other military and civilian applications of titanium alloys. Titanium and its alloys have become the ideal structural materials used for the fuselage, and accounted for a significant part of the structural quality in most military aircrafts. Titanium’s future market expectations need to be considered in the macro level market. Apart from the supply and demand trends of titanium market, it is necessary to consider the impact of technological innovations that can help to reduce the cost of titanium production.