Effect ofβ volume fraction on the dynamic grain growth during superplastic deformation of Ti3Al-based alloys

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.

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Investigation of Effect of Preliminary Annealing on Superplasticity of Ultrafine-Grained Conductor Aluminum Alloys Al-0.5%Mg-Sc

Materials ◽

10.3390/ma15010176 ◽

2021 ◽

Vol 15 (1) ◽

pp. 176

Author(s):

Mikhail Gryaznov ◽

Sergey Shotin ◽

Aleksey Nokhrin ◽

Vladimir Chuvil’deev ◽

Constantine Likhnitskii ◽

...

Keyword(s):

Grain Growth ◽

Volume Fraction ◽

Ultrafine Grained ◽

Preliminary Annealing ◽

Specimen Material ◽

Localization Of Plastic Deformation ◽

Long Time ◽

Elongation To Failure ◽

Maximum Volume Fraction ◽

Dynamic Grain Growth

Effect of preliminary precipitation of Al3Sc particles on the characteristics of superplastic conductor Al-0.5%Mg-X%Sc (X = 0.2, 0.3, 0.4, 0.5 wt.%) alloys with ultrafine-grained (UFG) microstructure has been studied. The precipitation of the Al3Sc particles took place during long-time annealing of the alloys at 300 °C. The preliminary annealing was shown to affect the superplasticity characteristics of the UFG Al-0.5%Mg-X%Sc alloys (the elongation to failure, yield stress, dynamic grain growth rate) weakly but to promote more intensive pore formation and to reduce the volume fraction of the recrystallized microstructure in the deformed and non-deformed parts of the aluminum alloy specimens. The dynamic grain growth was shown to go in the deformed specimen material nonuniformly–the maximum volume fraction of the recrystallized microstructure was observed in the regions of the localization of plastic deformation.

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Analysis of Dynamic Grain Growth Behavior during Superplastic Deformation Using a Grain Boundary Diffusion Mechanism

Journal of the Japan Institute of Metals and Materials ◽

10.2320/jinstmet1952.63.5_589 ◽

1999 ◽

Vol 63 (5) ◽

pp. 589-592

Author(s):

Byung-Nam Kim ◽

Keijiro Hiraga ◽

Yoshio Sakka ◽

Byung-Wook Ahn

Keyword(s):

Grain Boundary ◽

Grain Growth ◽

Superplastic Deformation ◽

Boundary Diffusion ◽

Diffusion Mechanism ◽

Growth Behavior ◽

Grain Boundary Diffusion ◽

Dynamic Grain Growth ◽

Grain Growth Behavior

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Grain Refinement in Titanium-Erbium Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052626 ◽

1974 ◽

Vol 32 ◽

pp. 522-523

Author(s):

B. B. Rath ◽

J. E. O'Neal ◽

R. J. Lederich

Keyword(s):

Electron Microscopy ◽

Size Distribution ◽

Grain Refinement ◽

Grain Growth ◽

Volume Fraction ◽

Pure Titanium ◽

Systematic Investigation ◽

Second Phase ◽

Titanium Matrix ◽

Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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Microstructural characterization of a rapidly solidified Al-Fe-V-Si alloy for elevated temperature applications

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104819 ◽

1988 ◽

Vol 46 ◽

pp. 550-551

Author(s):

R. E. Franck ◽

J. A. Hawk ◽

G. J. Shiflet

Keyword(s):

High Temperature ◽

Elevated Temperature ◽

Grain Growth ◽

Volume Fraction ◽

Microstructural Characterization ◽

Second Phase ◽

Microstructural Stability ◽

Elevated Temperature Strength ◽

Temperature Applications

Rapid solidification processing (RSP) is one method of producing high strength aluminum alloys for elevated temperature applications. Allied-Signal, Inc. has produced an Al-12.4 Fe-1.2 V-2.3 Si (composition in wt pct) alloy which possesses good microstructural stability up to 425°C. This alloy contains a high volume fraction (37 v/o) of fine nearly spherical, α-Al12(Fe, V)3Si dispersoids. The improved elevated temperature strength and stability of this alloy is due to the slower dispersoid coarsening rate of the silicide particles. Additionally, the high v/o of second phase particles should inhibit recrystallization and grain growth, and thus reduce any loss in strength due to long term, high temperature annealing.The focus of this research is to investigate microstructural changes induced by long term, high temperature static annealing heat-treatments. Annealing treatments for up to 1000 hours were carried out on this alloy at 500°C, 550°C and 600°C. Particle coarsening and/or recrystallization and grain growth would be accelerated in these temperature regimes.

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“Cavity” formation in superplastically deformed aluminium alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177921 ◽

1990 ◽

Vol 48 (4) ◽

pp. 958-959

Author(s):

A. Cziráki ◽

E. Ková-csetényi ◽

T. Torma ◽

T. Turmezey

Keyword(s):

Grain Boundaries ◽

Aluminium Alloys ◽

Superplastic Deformation ◽

Volume Fraction ◽

Superplastic Forming ◽

Polished Surface ◽

Cavity Formation ◽

Stress Concentrations ◽

Electron Microscopic ◽

Commercial Aluminium

It is known that the formation of cavities during superplastic deformation can be correlated with the development of stress concentrations at irregularities along grain boundaries such as particles, ledges and triple points. In commercial aluminium alloys Al-Fe-Si particles or other coarse constituents may play an important role in cavity formation.Cavity formation during superplastic deformation was studied by optical metallography and transmission scanning electron microscopic investigations on Al-Mg-Si and Al-Mg-Mn alloys. The structure of particles was characterized by selected area diffraction and X-ray micro analysis. The volume fraction of “voids” was determined on mechanically polished surface.It was found by electron microscopy that strongly deformed regions are formed during superplastic forming at grain boundaries and around coarse particles.According to electron diffraction measurements these areas consist of small micro crystallized regions. See Fig.l.Comparing the volume fraction and morphology of cavities found by optical microscopy a good correlation was established between that of micro crystalline regions.

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The Effect of Grain Size on Superplastic Deformation of Ti-6Al-4V Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.551-552.387 ◽

2007 ◽

Vol 551-552 ◽

pp. 387-392 ◽

Cited By ~ 4

Author(s):

Wen Juan Zhao ◽

Hua Ding ◽

D. Song ◽

F.R. Cao ◽

Hong Liang Hou

Keyword(s):

Grain Size ◽

Grain Growth ◽

Superplastic Deformation ◽

Initial Strain Rate ◽

Deformation Mode ◽

Tensile Tests ◽

Optical Microscope ◽

Coarse Grained ◽

Transmission Electron ◽

Grain Growth Model

In this study, superplastic tensile tests were carried out for Ti-6Al-4V alloy using different initial grain sizes (2.6 μm, 6.5μm and 16.2 μm) at a temperature of 920°C with an initial strain rate of 1×10-3 s-1. To get an insight into the effect of grain size on the superplastic deformation mechanisms, the microstructures of deformed alloy were investigated by using an optical microscope and transmission electron microscope (TEM). The results indicate that there is dramatic difference in the superplastic deformation mode of fine and coarse grained Ti-6Al-4V alloy. Meanwhile, grain growth induced by superplastic deformation has also been clearly observed during deformation process, and the grain growth model including the static and strain induced part during superplastic deformation was utilized to analyze the data of Ti-6Al-4V alloy.

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