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Author: Publisher: ISBN: Category : Languages : en Pages : 42
Book Description
The effect of alpha/beta solution temperature and cooling rate on the evolution of microstructure during the heat treatment of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti6242Si) with a partially-spheroidized starting microstructure of equiaxed + remnant lamellar alpha was established. Experiments comprising induction heating to a peak temperature of 971 or 982 degrees C followed by cooling at a rate of 11 or 42 degrees C/min revealed that the volume fraction of the equiaxed alpha grew much more rapidly than the lamellar constituent. These results were explained semi-quantitatively using simple diffusion analyses of the growth of either spherical or elliptical particles, taking into account the soft-impingement of the concentration fields. Despite the much lower diffusivity of molybdenum, which appears to control the growth of primary alpha in Ti6242Si, the similarity of the overall kinetics compared to those measured previously for Ti-6Al-4V was explained on the basis of the higher supersaturations developed during cooldown in the present alloy.
Author: Publisher: ISBN: Category : Languages : en Pages : 42
Book Description
The effect of alpha/beta solution temperature and cooling rate on the evolution of microstructure during the heat treatment of Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti6242Si) with a partially-spheroidized starting microstructure of equiaxed + remnant lamellar alpha was established. Experiments comprising induction heating to a peak temperature of 971 or 982 degrees C followed by cooling at a rate of 11 or 42 degrees C/min revealed that the volume fraction of the equiaxed alpha grew much more rapidly than the lamellar constituent. These results were explained semi-quantitatively using simple diffusion analyses of the growth of either spherical or elliptical particles, taking into account the soft-impingement of the concentration fields. Despite the much lower diffusivity of molybdenum, which appears to control the growth of primary alpha in Ti6242Si, the similarity of the overall kinetics compared to those measured previously for Ti-6Al-4V was explained on the basis of the higher supersaturations developed during cooldown in the present alloy.
Author: Publisher: ISBN: Category : Languages : en Pages : 37
Book Description
The static-coarsening behavior of the alpha-beta titanium alloy, Ti-6Al-4V, was established via a series of heat treatments at typical forging-preheat and final-heat-treatment temperatures followed by quantitative metallography. For this purpose, samples of an ultra-fine-grain-size (UFG) billet with a microstructure of equiaxed alpha in a beta matrix were heated at temperatures of 843,900,955, and 982 C for times between 0.25 and 144 h followed by water quenching. The coarsening of the primary alpha particles was found to follow r3-vs-time kinetics, typical of volume-diffusion-controlled behavior, at the three lower temperatures. At the highest temperature, the kinetics appeared to be fit equally well be an r3 of r4 dependence on time. The observations were interpreted in terms of the modified LSW theory considering the effects of volume fraction on kinetics and the fact that the phases are not terminal solid solutions. Prior models which take into account the overall source/sink effects of all particles on each other provided the best description of the observed dependence of coarsening on the volume fraction of primary alpha. In addition, the volume-diffusion kinetics derived for the UFG material were found to be capable of describing the coarsening behavior observed for industrial-scale billet of Ti-6Al-4V with a coarser starting equiaxed-alpha microstructure.
Author: Nageswara Rao Muktinutalapati Publisher: ISBN: Category : Electronic books Languages : en Pages : 0
Book Description
Heat treatment of metastable beta titanium alloys involves essentially two steps,Äîsolution treatment in beta or alpha+beta phase field and aging at appropriate lower temperatures. High strength in beta titanium alloys can be developed via solution treatment followed by aging by precipitating fine alpha (Œ±) particles in a beta (Œ≤) matrix. Volume fraction and morphology of Œ± determine the strength whereas ductility is dependent on the Œ≤ grain size. Solution treatment in (Œ±¬†+¬†Œ≤) range can give rise to a better combination of mechanical properties, compared to solution treatment in the Œ≤ range. However, aging at some temperatures may lead to a low/nil-ductility situation and this has to be taken into account while designing the aging step. Heating rate to aging temperature also has a significant effect on the microstructure and mechanical properties obtained after aging. In addition to Œ±, formation of intermediate phases such as omega, beta prime during decomposition of beta phase has been a subject of detailed studies. In addition to covering these issues, the review pays special attention to heat treatment of beta titanium alloys for biomedical applications, in view of the growing interest this class of alloys have been receiving.
Author: Publisher: ISBN: Category : Languages : en Pages : 57
Book Description
Rapid Heat Treatment (RHT) of commercial titanium alloys is a promising novel technology ensuring a high level of mechanical properties as well as high cost efficiency of processing. One of the significant advantages of RHT is related to the possibility of employing heating to temperatures in the single-phase beta field. By this means, the technique can be used to obtain fully lamellar intragrain microstructures favorable for high creep resistance and fracture toughness with relatively small or moderate size beta-grains. Such microstructures give rise to good tensile ductility and fatigue properties, comparable to those of equiaxed or bimodal microstructures. Therefore, fully lamellar microstructures with a controlled beta grain size of around 100 micrometers are a feasible way to balance the tensile, fatigue, and creep properties of titanium alloys. With direct resistance heating, these microstructures and the corresponding properties can be produced throughout the part uniformly. With induction heating, gradient type microstructures can be produced in which the properties of surface and core volumes of the heat-treated part are selectively controlled depending on the intended service application. In either case, an understanding of beta grain growth behavior during continuous, rapid heating is the key point. Thus, the goal of this investigation was to establish the temperature dependence of beta-grain size and its dependence on crystallographic texture for the alpha/beta alloy Ti-6A1-4V. The principal variables to be investigated include processing history, heating rate, and method of rapid heating (direct resistance or induction) in order to provide an explanation of beta-grain growth mechanism during continuous rapid heating. As a final output of this effort, practical recommendations for choosing RHT parameters to ensure optimized balance of mechanical properties will be developed.
Author: Publisher: ISBN: Category : Languages : en Pages : 73
Book Description
Titanium and titanium alloys are widely used for a variety of aerospace, chemical, marine, and other specialty applications because of their high strength, low density, good ductility, fatigue and corrosion resistance, as well as other properties. Depending on the application, a specific property (or combination of properties) can be obtained through microstructural modification. Microstructure evolution and control in titanium alloys is heavily dependent on the allotropic transformation from a hexagonal-close-packed crystal structure (denoted as alpha phase) found at low temperatures to a body-centered-cubic crystal structure (denoted as beta phase) at high temperatures. For pure titanium, this occurs at 882 deg C. In many titanium alloys, the beta phase is partially stabilized at lower temperatures, and the equilibrium volume fractions of alpha and beta vary with temperature. The temperature at which a specific alloy becomes entirely beta is called the beta transus. The conditions used for hot working and heating/heat treatment are often selected relative to the beta-transus temperature.
Author: H. J. Henning Publisher: ISBN: Category : Titanium alloys Languages : en Pages : 24
Book Description
The report discusses the current situation in beta forging of titanium alloys, based on a literature search plus the author's personal interviews with both using and forging industries. Manufacturers and users of beta forgings are listed in the report. Strength and fatigue properties of beta forgings are described and compared with the properties in structures forged by conventional means. Control of properties by microstructural control is discussed and illustrated by several photographs. Forging designs and practices are discussed. (Author).
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Author: A. J. Griest
Author: Faustine Ndali Busongo
Author: Zhendong Liu
Author: Nageswara Rao Muktinutalapati
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Author: C. T. Olofson
Author: H. J. Henning