DISSIMILAR TI ALLOYS WELDING FOR THE AUTOMOTIVE AND AVIATION SECTOR

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A survey of diffusion data of interstitial oxygen and of the substitutional elements aluminum and vanadium is presented for alpha and beta titanium. It is based on a survey of literature. Oxygen is an important interstitial element in titanium alloys. Oxygen’s large chemical affinity to titanium is indicated by Ti—O bond energy of 2.12 eV,1 comparable to the Ti—Ti bond energy of 2.56 eV.2 Oxygen is difficult to eliminate completely from titanium, and commercial titanium alloys usually contain from 0.10 to 0.20 wt pct oxygen. Oxygen significantly affects the mechanical properties of titanium alloys1,3 and is sometimes used as an alloying element. The effects of oxygen on phase transformation ,4,5,6 Youngs modulus,7,8 hardness,9,10 fracture toughness,11 and other mechanical properties12 have been amply documented. Aluminum and vanadium are the most frequently used substitutional alloying elements. Aluminum is an alpha stabilizer and vanadium is a beta stabilizer.

Event Abstract Back to Event Galvanic corrosion between CuNiTi arch wires and other metallic alloys for orthodontic applications Elisa Kassab1, 2 and José P. Gomes1 1 Federal University of Rio de Janeiro, Department of Metallurgy and Materials Science, Brazil 2 Pontifical Catholic University of Rio de Janeiro, Department of Metallurgy and Materials Science, Brazil Introduction: NiTi based alloys are widely used in biomedical applications due to their special mechanical properties, corrosion behaviour and biocompatibility[1]. As orthodontic wires, they deliver light and relative constant force, resulting in a more physiological dental movement. Addition of copper (Cu) as a third element can improve some mechanical properties desirable to their application as orthodontic wires, such as narrowing of stress hysteresis and a more stable stress-strain plateau[2]. However, the better mechanical properties are not accompanied by an increase in the corrosion behaviour. A recent report revealed a lower corrosion resistance of CuNiTi in physiological medium[3]. Using different metals in oral environment, for example as orthodontic arch wires and brackets, may result in galvanic corrosion. The aim of this work is to assess the galvanic corrosion of CuNiTi with other alloys commonly used in dentistry, such as stainless steel (SS) and beta titanium. Materials: The materials used for this work were the following: CuNiTi, SS and beta titanium arch wires. CuNiTi was an 0.18-inch heat activated (35 oC) arch wire from Ormco Corp. (Orange, USA). SS and beta titanium wires were 0.16-inch arch wires ordered from GAC International Inc. (New York, USA). Methods: Electrochemical tests were performed in 0.9% NaCl electrolyte in order to simulate physiological solution. A conventional three electrode cell with a saturated calomel electrode as a reference electrode and platinum as a counter electrode was used. This cell was connected to a potentiostat (Metrohm Autolab). Potentiodynamic polarization was conducted at a scan rate of 20 mV/min starting from -600 mV to 800 mV. Cathodic curves of the materials with higher corrosion potentials (SS and beta titanium) were overlaid with the anodic curve of the CuNiTi. At this intersection point, the value corresponding to x axis was determined as the estimated potential of the galvanic couple (Ecouple) and y axis as the estimated current from the galvanic couple (icouple). Results: Initial results indicate an electrode potential gap between CuNiTi and SS and titanium alloys in 0.9 NaCl solution. This suggests that galvanic corrosion might occur in this environment. Mean Ecouple measured for the CuNiTi/SS couple was -0.1 mV. For CuNiTi/titanium was -0.8 mV. A typical polarization curve for CuNiTi and titanium is shown in Figure 1. Direct galvanic coupling and potentiostatic experiments will be performed for CuNiTi/SS and CuNiTi/titanium couples. Discussion: In dentistry, there are usually two or more different metals together in a potential corrosive environment. Therefore, galvanic corrosion must be investigated. Potentiodynamic curves revealed that for both couples, CuNiTi/SS and CuNiTi/titanium, CuNiTi would act as an anode, and therefore, would corrode faster than it would alone. As a result of corrosion, deterioration of the arch wire surface may occur and the mechanic properties of CuNiTi wires could be altered, delaying orthodontic treatment. Moreover, CuNiTi corrosion might affect the material biocompatibility due to release of potential allergic Ni ion. Conclusion: CuNiTi might be susceptible to galvanic corrosion in oral environment when coupled to more noble materials, such as SS and titanium. This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); and the Fundação Coordenação de Projetos, Pesquisas e Estudos Tecnológicos (Fundação COPPETEC).

Interfacial microstructure evolution and mechanical response of TC19/Ti150 dissimilar joints obtained by diffusion bonding

This article introduces the different types, distinctions, and grades of commercially pure titanium and titanium alloys. It describes three types of alloying elements: alpha stabilizers, beta stabilizers, and neutral additions. The article discusses the basic categories of titanium alloys, namely, alpha and near-alpha titanium alloys, beta and near-beta titanium alloys, and alpha-beta titanium alloys. It also describes the general microstructural features of titanium alloys.

Global and Local Mechanical Properties and Microstructure of Friction Stir Welds with Dissimilar Materials and/or Thicknesses

Friction stir welding of titanium alloys: A review

Metallic structural components made from dissimilar titanium alloys are playing important roles in high-end industries such as aerospace and aviation. In this paper, a Ti-5Al-2.5Sn/Ti-6Al-4V dissimilar titanium alloy material was additively manufactured by the selective laser melting (SLM) process. Interface characteristics, microstructure, and mechanical properties of the SLM-deposited samples before and after complete annealing treatment were researched to provide some technical basics for the integral fabrication of dissimilar titanium alloy components. The results demonstrated that a defect-free metallurgical bonded interface with a ~ 70-μm-wide element inter-diffusion region could be obtained between the Ti-5Al-2.5Sn and Ti-6Al-4V layers under both the as-deposited and the complete annealing states. The interfacial bonding strength between the dissimilar titanium alloys was always higher than the strength of the Ti-5Al-2.5Sn layers. Microstructure evolution and element inter-diffusion mechanisms of the SLM-produced Ti-5Al-2.5Sn/Ti-6Al-4V samples were also revealed and related to the change in mechanical properties.

traction and propulsion are fundamental for sustainable mobility, with electric vehicles but also with other transportation means as trains and boats. Its current state of development and deployment is expected to increase the search for graduated people and foster employment on the electric vehicles' and related components' research, development, design, manufacturing, testing and servicing fields. In this paper, the experience on teaching and learning about electric vehicles and electric traction at the Polytechnic of Coimbra, namely in the frame of its electrical engineering master course, is presented, where the Electric Traction and Vehicles master's subject addresses mainly four topics: importance, problems and solutions for sustainable mobility; electric road vehicles; railway electric traction; and an introduction to electric boats. Other aspects of learning are also presented, through some BSc, master and research a development projects description.

Automobiles as a new means of road transport had to compete with horses at the end of the 19th century. Automobiles won the competition because they were faster, cheaper to operate, and produced less pollution. The potential consumer had a choice between vehicles with electric, internal combustion or steam engines in the 1900s. Electric vehicles were considered as more reliable and cost effective. Mass production made gasoline vehicles affordable and easy-to-use. Electric vehicles lost the competition with them since 1910s. Air pollution in large cities has renewed the interest in electric vehicles at the end of the 20th century. Expressions for estimation of well to wheel energy efficiency of electric and gasoline vehicles in miles per gallon have been obtained. Electric vehicles are more well to wheel energy efficient than gasoline cars. Price-performance ratio for electric vehicles today is higher than it was in the 1900s.

Automobiles as a new means of road transport had to compete with horses at the end of the 19th century. Automobiles won the competition because they were faster, cheaper to operate, and produced less pollution. The potential consumer had a choice between vehicles with electric, internal combustion or steam engines in the 1900s. Electric vehicles were considered as more reliable and cost effective. Mass production made gasoline vehicles affordable and easy-to-use. Electric vehicles lost the competition with them since 1910s. Air pollution in large cities has renewed the interest in electric vehicles at the end of the 20th century. Expressions for estimation of well to wheel energy efficiency of electric and gasoline vehicles in miles per gallon have been obtained. Electric vehicles are more well to wheel energy efficient than gasoline cars. Price-performance ratio for electric vehicles today is higher than it was in the 1900s.

IMI 834 Titanium alloy is a near alpha (hcp) titanium alloy used for high temperature applications with the service temperature up to 600°C. Generally, this alloy is widely used in gas turbine engine applications such as low pressure compressor discs. For these applications, good fatigue and creep properties are required, which have been noticed better in a bimodal microstructure, containing 15-20% volume fraction of primary alpha grains (αp) and remaining bcc beta (β) grains transformed secondary alpha laths (αs). The bimodal microstructure is achieved during processing of IMI 834 in the high temperature α+β region. The major issue of bimodal IMI 834 during utilization is its poor dwell fatigue life time caused by textured macrozones. Textured macrozone is the spatial accumulation of similar oriented grains in the microstructure generated during hot processing in the high temperature α+β region. Textured macrozone can be mitigated by controlling the hot deformation with certain strain rate under stable plastic conditions having β grains undergoing dynamic recrystallization. Hence, a comprehensive study is required to understand the deformation behavior of α and β grains at different strain rates in that region. Hot compression tests up to 5°% strain of the samples are performed with five different strain rates i.e. 10-3 s-1, 10-2 s-1, 10-1 s-1, 1 s-1 and 10 s-1 at 1000°C using Gleeble 3800. The resultant bimodal microstructure and the texture studies of primary alpha grains (αp) and secondary alpha laths (αs) are carried out using scanning electron microscopy (SEM)-electron back scattered diffraction (EBSD) method.

. Production efficiency as well as the reduction of energy consumption and waste are the main drivers for the improvement of large-scale production in chemical industry. In addition, the demand for new processes – these days especially related to the chemical energy conversion as basis for the Energiewende – are additional triggers for innovation. Catalysis, well recognized by the public e.g. in form of the 3-way automobile catalyst, plays an important role for about 90% of all processes in chemical industry. The development of new and improved catalysts is a challenge for chemists – as is the search for new structural materials for mechanical engineers. Due to the often-necessary noble and thus expensive metals (e.g. palladium) in many catalysts, structural and chemical function have been developed separately in the two communities. Recent progress in catalytically active materials allows replacing expensive noble metals in selected catalytic processes by significant cheaper elements [1]. This offers the new perspective to combine structural and chemical functionality by innovative materials. Within this area, intermetallic compounds with their peculiar combination of crystal and electronic structure [2], represent an interesting class of materials to address this vision as will be shown in the contribution.

Distribution and thermal desorption behavior of hydrogen in titanium alloys immersed in acidic fluoride solutions

With the advent of the new era, more and more heavy polluting industries emerge. Modern people pay more and more attention to low-carbon and environmental protection, which is also a way of green travel. The country also has many new policies for green travel. In addition to walking, cycling and mass transportation, as a new type of energy industry, the environmental protection function of electric vehicle is increasingly obvious, and it is also regarded as the least carbon emission vehicle. Compared with the large amount of exhaust caused by automobile, electric vehicle has great significance for ecological and environmental protection. As a result, electric vehicles based on green travel are emerging. It can well solve the problems of people’s travel destination, short distance and long travel time caused by traffic congestion. Designers will take people’s “green” travel mode as the fundamental principle, and promote electric vehicles to a higher level of travel mode choice, which will be different from the previous travel tool with labor saving as the first consideration. In many people’s minds, the electric car is a poor safety, loss of identity means of transportation. Moreover, in many cities, the emergence of electric vehicles is just a convenient and cheap means of transportation that has to be replaced for the purpose of “anti-friction order”. However, with the rapid development of the core technology of electric vehicles and the continuous improvement of residents’ quality of life, people’s choice of green and environmentally friendly means of transportation has been greatly improved. Based on the interval measurement algorithm, this paper makes a series of research and demonstration on the design of electric vehicles for green travel. Although many people already have a car at home as a means of transportation, they will still buy an electric car, because it has great advantages for short-distance green travel. The experimental results show that it is of great significance to design an electric vehicle based on green travel mode in modern society.