Search results for "titanium alloy"
showing 10 items of 86 documents
Phase evolution in hot forging of dual phase titanium alloys: Experiments and numerical analysis
2014
Abstract Modern aeronautical and aerospace industries must face the demanding challenge of reducing operational consumption and production costs coming from materials and labor. Current trend of engineering is oriented to meet both requirements increasing the use of materials characterized by high specific resistance as titanium alloys. Hot forging can be used to reduce the production costs of titanium components: forging in closed dies of billets or semi-finished forms, at different temperatures above or below the β-transus temperature, allows the production of complex shapes with limited amount of edge trim removal and machining rework after forging. Unfortunately, as far as Ti–6Al–4V tit…
Joining Ti6Al4V and AISI 304 through friction stir welding of lap joints: experimental and numerical analysis
2014
The results of an experimental and numerical analysis on Friction Stir Welding of dissimilar lap joints made out of AISI304 and Ti-6Al-4 V thin sheets are presented. The mixed joints, welded with varying process parameters, have been characterized from a mechanical and metallurgical point of view. A numerical model able to take into account the behaviour of the two different materials has been used. The numerical results have been utilized to explain the joint properties and the occurring material flow. The effect of the heat input, tilt angle and sheets mutual position has been investigated. It is found that both hooking defects and tunnels may occur with incorrect choice of process parame…
The combined effect of refractory coatings containing reactive elements on high temperature oxidation behavior of chromia-forming alloys
2003
Abstract The high temperature oxidation behaviors of chromia-forming alloys (F17Ti and Fe–30Cr alloys) have been studied at 1273 K under isothermal conditions and at 1223 K under cyclic conditions, in air under the atmospheric pressure. To extend the oxidation lifetime, coatings have been applied onto the alloy surfaces. Al2O3 and Cr2O3 films doped with Sm2O3 or Nd2O3 were prepared via the metal-organic chemical vapor deposition technique. Single Cr2O3, Al2O3, Nd2O3 and codeposited Cr2O3–Nd2O3, Al2O3–Nd2O3, Al2O3–Sm2O3 coatings drastically improved the chromia-forming alloy high temperature oxidation behavior, since they decreased the oxidation rate and enhanced the oxide scale adhesion. Re…
Role of plastic deformation and microstructure in the micro-electrochemical behaviour of Ti–6Al–4V in sodium chloride solution
2013
Abstract The role of alloying elements and the influence of plastic deformation on the micro-electrochemical behaviour and the pitting corrosion susceptibility of TiAl6V4 have been investigated in 10 g/L NaCl using the electrochemical microcell technique. Local electrochemical measurements have revealed that both the increase of surface roughness and the increase of dislocation density have impact on the electrochemical behaviour of TiAl6V4 after plastic deformation. It has been shown the surface roughness induced by slip band emergence is the predominant parameter responsible for the increase of the cathodic current. It has also been shown that cathodic reactions occur preferentially at su…
Technological aspects regarding machining the titanium alloys by means of incremental forming
2017
Titanium alloys are materials with reduced formability, due to their low plasticity. However, today there are high demands regarding their use in the automotive industry and in bio-medical industry, for prosthetic devices. This paper presents some technological aspects regarding the machinability of titanium alloys by means of incremental forming. The research presented in this paper aimed to demonstrate that the parts made from these materials could be machined at room temperature, in certain technological conditions.
Beta forging of Ti-6Al-4V: Microstructure evolution and mechanical properties
2013
Titanium alloys are finding an increasing use in the aeronautical field, due to their characteristics of high mechanical properties, lightness and corrosion resistance. Moreover these alloys are compatible with the carbon fibre reinforced plastics that are also finding a wide use in the aeronautical field. On the other hand the use of these alloys implies some drawbacks, for example titanium alloys are often considered more difficult to form and generally have less predictable forming characteristics than other metallic alloys such as steel and aluminum. In this paper was studied both the microstructure evolution and the mechanical properties of a Ti-6Al-4V rolled bar after hot forging. The…
Evolution of microstructures and mechanical properties during dissimilar electron beam welding of titanium alloy to stainless steel via copper interl…
2013
Abstract The influence of operational parameters on the local phase composition and mechanical stability of the electron beam welds between titanium alloy and AISI 316L austenitic stainless steel with a copper foil as an intermediate layer has been studied. It was shown that two types of weld morphologies could be obtained depending on beam offset from the center line. Beam shift toward the titanium alloy side results in formation of a large amount of the brittle TiFe2 phase, which is located at the steel/melted zone interface and leads to reducing the mechanical resistance of the weld. Beam shift toward the steel side inhibits the melting of titanium alloy and, so, the formation of brittle…
Computer Aided Design of an Effective Fixture for FSW Processes of Titanium Alloys
2011
During the last years welded titanium components have been extensively applied in aeronautical and aerospace industries because of their high specific strength and corrosion resistance properties. Friction Stir Welding (FSW) is a solid state welding process, currently industrially utilized for difficult to be welded or “unweldable” aluminum and magnesium alloys, able to overcome the drawbacks of traditional fusion welding techniques. When titanium alloys are concerned, additional problems arise as the need for very high strength and high temperature resistant tools, gas shield protection and high stiffness machines. Additionally, the process is characterized by an elevated sensitivity to te…
The formation of intermetallics in dissimilar Ti6Al4V/copper/AISI 316 L electron beam and Nd:YAG laser joints
2011
Abstract The welds of titanium alloys with steels suffer from the brittleness of resulting intermetallic compounds. In present study, we report the feasibility of Ti6Al4V to stainless steel AISI 316L welding through pure copper interlayer carried out by electron beam and pulsed Nd:YAG laser. The nature and the localization of intermetallic phases in these welds have been studied by SEM, EDS, XRD and microhardness measurements. The simplified scenario of weld formation has been proposed in order to understand the mechanism of weld formation and to explain the way local phase content determines the mechanical properties. It can be concluded that the insertion of 500 μm pure copper interlayer …
Beta-forging of Ti6Al4V titanium alloy powders consolidated by HIP: Plastic flow and strain-rate relation
2014
Ti6Al4V is probably the best known and studied titanium alloy, not only for aerospace applications. Nevertheless the deformation behavior still represents a challenge if any modification in the deformation process is required or introduced. This work deals with deformation behavior description of Ti6Al4V HIPped powders during high temperature deformation tests carried on in the Beta-region. Laboratory compression and tensile tests have been coupled with relaxation tests in order to achieve robust data about strain rate sensibility m-coefficient and activation energy Q. These results have been fitted for the assessment of a more general exponential deformation law. The final result is a “Dor…