Papers by Keyword: TiAl

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Authors: Jiao Luo, Miao Quan Li, Y.Q. Hu
Abstract: A constitutive equation has been established to describe the effect of grain size on the deformation behavior of Ti-6.62Al-5.14Sn-1.82Zr alloy during the high temperature. In this paper, firstly a steady flow stress model is proposed, and a function relating to the grain size is introduced to modify the steady flow stress model. Meanwhile, a microstructure model established by the fuzzy neural network method is applied to calculate the grain size of prior α phase during the high temperature deformation of Ti-6.62Al-5.14Sn-1.82Zr alloy. The calculated flow stress using the present constitutive equation shows a good agreement with the experimental flow stress of the Ti-6.62Al-5.14Sn-1.82Zr alloy. The relative maximum error was not more than 15%.
Authors: Ning He, Liang Li, X.L. Li
Abstract: Gas cooled cutting is an important branch of green machining technology with its excellent cooling performance and is used more and more widely in field of machining. A new method of developing cooling gas generator using semiconductor refrigeration is presented in this paper. Then the main principle, structure and performance of the generator are introduced. In addition, the experiments of high speed milling of Ti Alloy using cooled nitrogen gas were conducted and satisfactory results were achieved. These researches show that the new cooling gas generator has a series of merits such as simple structure, excellent performance, handy operation, low cost and significant spreading value etc.
Authors: Dana Rohanová, Aleš Helebrant, P. Haufová, Lukáš Brázda, Petr Bezdička
Abstract: This paper performs a new way of a resorbable surface on Ti alloy preparation. Precalcification of a chemically treated Ti or Ti alloy surface by a supersaturated calcification solution - SCS2 (high content of Ca2+ as well as (PO4)3- ions) allows to short of an induction period in SBF solution (practically immediate reaction stats a hydroxyapatite precipitation). Soluble octacalcium phosphate (Ca8H2(PO4)6. 5H2O was detected by RTG on the surface after calcification. Presumption is: a healing time of the calcified Ti alloy could be shortened.
Authors: Ji Lin Yu, Xin Long Dong, Jiang Yue Zhang
Authors: Ho Sung Lee, Jong Hoon Yoon, Yeong Moo Yi
Abstract: The surface oxidation behavior was investigated over a range of solid state bonding condition of the Ti-6Al-4V ELI alloy. Since the oxides at the bonding interface may prevent the materials from complete bonding, it is important to understand the oxidation behavior at solid state bonding condition. The activation energy of oxidation of Ti-6Al-4V ELI is estimated to be 318 KJ/mol in an environment of solid state bonding process. For Ti-6Al-4V ELI alloy, strucutral integrity of bonding interface without oxides have been obtained at 850°C applying pressure of 3MPa for 1 hour. Solid state diffusion bonding of Ti-15V-3Cr-3Sn-3Al alloy was also obtained under a pressure of 6MPa for 3 hours at 925°C.
Authors: W. Li, Tong Xing, Bao Xiang Qiu, Gang Xiang Hu, Yang Fu Jin
Abstract: A reasonable finite element (FE) model of grinding temperature field has been developed on the basis of analysis of the transient temperature field, and three kinds of boundary conditions are loaded on the element of a moving heat source. The study, which is based on the finite element principle, has been carried out using the numerical simulation software ANSYS. Many results have been obtained including three dimensional temperature distribution map. The simulated results under different conditions show good agreement with the experimental results. With the comparison of the dry-grinding and wet-grinding, the result shows that the wet-grinding temperature with a proper grinding fluid is rather lower than the dry-grinding temperature. Finally, the variable coefficient of convective heat transfer and the different form heat source have been discussed in detail.
Authors: Adriana F. Azevedo, N.G. Ferreira, Vladimir J. Trava-Airoldi, Evaldo Jose Corat
Authors: Fernando Gomes, Joaquim Barbosa, Carlos Silva Ribeiro
Abstract: Melting TiAl based alloys in ceramic crucibles often leads to chemical contamination, alloy heterogeneity and non-metallic inclusions. The severity of such phenomena usually depends on the nature of crucible materials, the melting stock composition and the melting parameters, namely superheating time and temperature and melting pressure. Among the referred drawbacks, Al loss during melting is a critical aspect, as its concentration in TiAl based alloys has a very strong effect in their mechanical properties. Although a few studies of critical factors affecting the evaporation behaviour of Al during electron beam and induction skull melting of Ti-Al alloys had been carried out, until now no information was released on this subject for the ceramic crucible induction melting process. In this work a Ti-48Al alloy was induction melted in a zircon crucible with Y2O3 inner layer, using 50 and 100 °C superheating temperatures and 0, 60 and 90 second holding times, and poured into a graphite mould. The effect of different temperature/time combinations in the alloy composition, Al loss by evaporation and extent of the metal/crucible interaction was studied for different melting pressures. Al loss was found to increase significantly for melting pressures below around 10-1 mbar, at a rate that increases as melting pressure decreases, until a maximum rate is reached, remaining constant for lower pressure levels. Metal/crucible interaction increased directly with the melting pressure and superheating time, leading to alloy contamination with yttrium and oxygen. For the experimental set-up and conditions used on this work, optimal superheating time/pressure combinations that lead to acceptable alloy composition and sanity have been identified.
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