The Effect of Small Amounts of Yttrium Addition on Static and under Superplastic Deformation Grain Growth in Newly Developed α+β Type, Ti-4.5Al-6Nb-2Mo-2Fe Alloy

2006 ◽  
Vol 15-17 ◽  
pp. 970-975 ◽  
Author(s):  
Behrang Poorganji ◽  
S. Hotta ◽  
Taichi Murakami ◽  
Takayuki Narushima ◽  
Yasutaka Iguchi ◽  
...  
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Growth ◽  
Hot Deformation ◽  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Growth Behavior ◽  
Two Phase ◽  
Yttrium Addition ◽  
Grain Growth Behavior

New α+β type titanium alloy with Ti-4.5Al-6Nb-2Mo-2Fe was developed on the basis of using biocompatible elements and eliminating the cytotoxic ones such as Vanadium, while achieving the desirable mechanical properties such as appropriate strength, cold workability and low superplastic forming (SPF) temperature. The present study was conducted to investigate the effect of yttrium addition of less than 0.05% into this alloy on static and under superplastic deformation grain growth behavior. The new alloy bar manufactured by α+β processing and annealed at 1073K yielded extremely fine two-phase microstructure with α grain size around 2μm. Specimens were heated at temperatures of 1048, 1073 and 1098K and kept for times between 3.6 to 172.8KS. Yttrium forms in-situ Y2O3 particles, and the presence of these particles yield finer two phase microstructure due to their retardation effect on β phase grain growth. Grain growth behavior during hot deformation was investigated by hot compression test in use of a hot working simulator of THERMEC-Master Z. Strain rate was varied from 2×10-2 to 2×10-4S-1 and strain was 0.69. Grain size of both α and β phases increased with a reduction of strain rate, and Y2O3 particle was also effective to retard grain growth under hot deformation. It was confirmed from comparison of grain growth during isothermal heating with and without hot deformation that grain growth was much accelerated by deformation. All of these results were discussed based on grain growth mechanism or model for two-phase microstructures as well as superplastic deformation mechanism.

Recrystallization and Grain Growth Behavior of Alloy 718 Casting during Hot Working

2007 ◽  
Vol 345-346 ◽  
pp. 57-60 ◽  
Author(s):  
Jong Won Yoon ◽  
Nam Yong Kim ◽  
Jeoung Han Kim ◽  
Jong Taek Yeom ◽  
Nho Kwang Park
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Growth ◽  
Growth Behavior ◽  
Area Fraction ◽  
Alloy 718 ◽  
Recrystallization Behavior ◽  
Temperature Range ◽  
Average Grain Size ◽  
Grain Growth Behavior

Recrystallization and grain growth behavior of alloy 718 casting were investigated to obtain homogeneous microstructure during hot forging. For this purpose, compression tests were carried out for cylindrical specimens at the temperature range of 1000 to 1150°C and the strain rate of 10-1 and 10sec-1. The dynamic recrystallization behavior caused by the hot compression was investigated in terms of the recrystallized area fraction and average grain size. Reheating was followed to the hot compressed samples at the temperature range of 1050 to 1150°C for 100, 600 and 1800sec, and the static recrystallization behavior caused by the reheating was also investigated. As hot deformation temperature increased from 1000 to 1150°C, both the area fraction and average grain size of dynamically recrystallized grains increased. When higher strain rate of 10 sec-1 was used, the area fraction of dynamically recrystallized grains increased substantially, but the average grain size was not affected. When reheating the hot compressed samples at 1050°C for 100, 600 and 1800sec, respectively, microstructural change including grain growth was not noticed. On the other hand, when reheating the samples at higher temperatures, 1100°C and 1150°C, both the area fraction and the average grain size of the statically recrystallized grains increased considerably as the holding time increased from 100 to 1800sec.

Effects of grain size and porosity on strength of Li 2 TiO 3 tritium breeding pebbles and its grain growth behavior

2016 ◽  
Vol 482 ◽  
pp. 163-169 ◽  
Author(s):  
Maoqiao Xiang ◽  
Yingchun Zhang ◽  
Yun Zhang ◽  
Chaofu Wang ◽  
Wei Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Growth Behavior ◽  
Tritium Breeding ◽  
Grain Growth Behavior

A TEM characterization of precipitates evolution and their effect on the grain-growth behavior of gas atomized superalloy A-286

1992 ◽  
Vol 50 (1) ◽  
pp. 178-179
Author(s):  
Keesam Shin
Keyword(s):  
Grain Size ◽  
Sample Preparation ◽  
Grain Growth ◽  
Smooth Surface ◽  
Growth Behavior ◽  
Tem Characterization ◽  
Heat Treated ◽  
Thin Electron ◽  
Grain Growth Behavior

It is generally accepted that the refined grain size and stable grain boundaries observed in rapid-solidification-processed (RSP) materials are due to the fine precipitates produced during and after the processing. This is based on the observation of the materials after consolidation of the powders. Though there is little doubt that the as-atomized powder structure is crucial for the understanding of the consolidated sample, there are few studies of the powder. This is mainly because of the difficulty in preparation of thin electron-transparent samples.The most common method of powder sample preparation uses two or three different embedding materials whose polishing conditions are usually not identical. In this study, a monolayer of powder was gold coated, electroplated with nickel, and then electropolished. Electropolishing provided a nice and smooth surface without any surface artifact. In this study, as-atomized and heat treated powders were studied by TEM (JEOL JEM 200CX) and STEM (VG HB501). Because of the fineness of the defects involved, TEM observation is crucial.

Grain growth behavior in Fe3Al alloys fabricated by different methods

1994 ◽  
Vol 9 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
B.H. Rabin ◽  
J.K. Wright ◽  
R.N. Wright ◽  
C.H. Sellers
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Growth Behavior ◽  
Elemental Powder ◽  
Ingot Metallurgy ◽  
Prealloyed Powder ◽  
The Difference ◽  
Grain Growth Behavior

Grain sizes were measured after various heat treatments in three Fe3Al alloys having similar composition that were fabricated using the techniques of ingot metallurgy (cast and wrought), hot extrusion of prealloyed powder, and hot isostatic pressing (HIP) of elemental powders. The ingot metallurgy (I/M) material exhibited normal grain growth behavior at temperatures above 750 °C, in agreement with previous observations. Both powder metallurgy (P/M) materials displayed unusual resistance to grain growth compared to the I/M alloy. In the case of the prealloyed P/M material, the initial (recrystallized) grain size was larger than the initial grain size of the I/M material, although little grain growth was observed for heat-treatment temperatures up to 1100 °C. At higher temperatures grain growth occurred at a rate comparable to that observed to the I/M alloy. The elemental powder P/M material exhibited similar grain growth behavior to the prealloyed P/M material, although the initial (as-HIPed) grain size was considerably smaller. Transmission electron microscopy (TEM) indicated that the grain growth resistance of the P/M materials could be attributed to grain boundary pinning by oxide particles presumed to originate from the powder particle surfaces. The difference in the stable grain size between the prealloyed and elemental powder P/M materials was attributed to the nature of the particle dispersions resulting from processing.

The Effect of Deformation and Reinforcement Particles on the Grain Growth Behavior of MoSi2

1993 ◽  
Vol 322 ◽  
Author(s):  
Ajoy Basu ◽  
Amit Ghosh
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
High Growth ◽  
Growth Behavior ◽  
Dislocation Creep ◽  
Grain Boundary Mobility ◽  
Agglomeration Effects ◽  
Static Annealing ◽  
Grain Growth Kinetics ◽  
Grain Growth Behavior

AbstractThe grain growth behavior of polycrystalline MoSi2 and composites containing SiC particulates has been studied in the temperature range of 1200-1800°C during static annealing as well as under concurrent deformation conditions. Monolithic MoSi2, with ∼ 26 μm grain size appears to be extremely resistant to grain growth up to 1500°C. However, the grain growth rate above this temperature is quite rapid. When particulate reinforcements are used to reduce the grain size of MoSi2 to 4.4 μm, a stable microstructure is maintained up to 1500°C. Accelerated grain growth kinetics are observed at 1800°C under conditions of large plastic strain. This enhanced grain boundary mobility is associated with particle sweeping and particle agglomeration effects. At lower temperatures, where dislocation creep is the more dominant deformation mechanism these effects are absent. In the presence of a Si concentration gradient extremely high growth rates of columnar MoSi2 grains have been observed during reaction synthesis of MoSi2.

Step Free Energy Change and Microstructural Development in BaTiO3-SiO2

2007 ◽  
Vol 352 ◽  
pp. 25-30 ◽  
Author(s):  
Jaem Yung Chang ◽  
Suk Joong L. Kang
Keyword(s):  
Free Energy ◽  
Grain Growth ◽  
Driving Force ◽  
Growth Behavior ◽  
Abnormal Grain Growth ◽  
Free Energy Change ◽  
Energy Change ◽  
Microstructural Development ◽  
Two Phase ◽  
Grain Growth Behavior

The effect of step free energy on the grain growth behavior in a liquid matrix is studied in a model system BaTiO3-SiO2. BaTiO3-10SiO2 (mole %) powder compacts were sintered at 1280°C under various oxygen partial pressures (PO2), 0.2, ~ 10-17 and ~ 10-24 atm. As the step free energy decreases with the reduction of PO2, it was possible to observe the change in growth behavior with the reduction of the step free energy. At PO2 = 0.2 atm, essentially no grain growth (stagnant grain growth) occurred during sintering up to 50 h. At PO2 ≈ 10-17 atm, abnormal grain growth followed stagnant grain growth during extended sintering (incubation of abnormal grain growth). At PO2 ≈ 10-24 atm, normal grain growth occurred. These changes in growth behavior with PO2 and the step free energy reduction are explained in terms of the change in the critical driving force for appreciable growth relative to the maximum driving force for grain growth. The present experimental results provide an example of microstructure control in solid-liquid two- phase systems via step free energy change.

scholarly journals Superplastic Behaviour of Ti54M and Ti64

2020 ◽  
Vol 321 ◽  
pp. 04028
Author(s):  
Paranjayee Mandal ◽  
Ares Gomez-Gallegos ◽  
Diego Gonzalez ◽  
Hosam Elrakayby ◽  
Paul Blackwell
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Grain Growth ◽  
Superplastic Deformation ◽  
Volume Fraction ◽  
Grain Boundary Sliding ◽  
Superplastic Behaviour ◽  
Average Grain Size ◽  
Lower Temperature ◽  
Superplastic Properties

Even though TIMETAL-54M (Ti-5Al-4V-0.6Mo-0.4Fe or Ti54M) has been commercially available for over 10 years, further study of its superplastic properties is still required in order to assess its applicability within the aerospace industry as a potential replacement for other commercial titanium alloys such as Ti-6Al-4V (Ti64). Ti54M is expected to obtain superplastic characteristics at a lower temperature than Ti64 due to its lower beta-transus temperature. The superplastic forming (SPF) capability of alloys that can be formed at lower temperatures has always attracted the interest of industry as it reduces the grain growth and alpha-case formation, leading to longer life for costly high temperature resistant forming tools. In this work, the SPF characteristics of both Ti54M and Ti64 have been examined by conducting tensile tests according to the ASTM E2448 standard within a range of temperatures and strain values at a fixed strain rate of 1 × 10-4/S. A high strain rate sensitivity and uniform deformation at high strains are key indicators in selecting the optimum superplastic temperature. This was observed at 815˚C and 925˚C for Ti54M and Ti64 respectively. The tensile samples were water quenched to freeze their respective microstructure evolution following superplastic deformation and SEM images were captured for grain size and volume fraction of alpha-phase analyses. A slightly higher alpha-grain growth rate was observed during superplastic deformation of Ti64. The initial fine-grain microstructure of Ti54M (~1.6 micron) resulted in a final microstructure with an average grain size of ~3.4 micron and optimum the alpha/beta ratio. Both the fine-grained microstructure and increased amount of beta-volume fraction promotes the superplastic behaviour of Ti54M by grain boundary sliding (GBS). Thus superplastic properties were observed for Ti54M at a lower temperature (~100˚C) than for Ti64.

Thermal Stability of Nanocrystalline Inconel 718 and Ni Prepared by High Velocity Oxy-Fuel (HVOF) Thermal Spraying

1998 ◽  
Author(s):  
H.G. Jiang ◽  
M.L. Lau ◽  
E.J. Lavernia
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
Grain Growth ◽  
High Velocity ◽  
Inconel 718 ◽  
Isothermal Annealing ◽  
Growth Behavior ◽  
Hvof Spraying ◽  
Grain Growth Behavior ◽  
Thermal Stability Of

Abstract Nanocrystalline Inconel 718 and Ni powders were prepared using two approaches: methanol and cryogenic attritor milling. High velocity oxy-fuel (HVOF) spraying of milled Inconel 718 powders was then utilized to produce Inconel 718 coatings with a nanocrystalline grain size. Isothermal heat treatments were carried out to study the thermal stability of the methanol milled and cryomilled Inconel 718 powders, as well as the HVOF Inconel 718 coatings. All nanocrystalline Inconel 718 powders and coatings studied herein exhibited significant thermal stability against grain growth as evidenced by a grain size around 100 nm following annealing at 1273 K for 60 min. In the case of the cryomilled nanocrystalline Ni powders, isothermal grain growth behavior was studied, from which the parameters required for the prediction of the microstructural evolution during a non-isothermal annealing were acquired. The theoretical simulation of grain growth behavior of nanocrystalline Ni during non-isothermal annealing conditions yields results that are in good correspondence with the experimental results.

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