High Temperature Deformation Behavior of Titanium-Aluminide Based Gamma Plus Beta Microduplex Alloy.

Masahashi, Naoya; Mizuhara, Y.; Matsuo, Munetsugu; Hanamura, Toshihiro; Kimura, Masao; Hashimoto, Keizo

doi:10.2355/isijinternational.31.728

Cited by 75 publications

(16 citation statements)

References 2 publications

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“…However, when the grain size is smaller (i.e., ≤10 m), m for relatively low strain rates increases dramatically with grain refinement. [13][14][15][16][17][18] Plots of log p vs reciprocal temperature shown in linear plots in Figure 4(a) varies from 3350 to 5500 K depending on the strain rate. An apparent activation energy, Q, can be calculated as Q ϭ 2.303 RS/m, where R is the universal gas constant.…”

Section: A Plastic Flow Phenomenologymentioning

confidence: 99%

“…Tensile deformation and fracture of near gamma titanium aluminide alloys at elevated temperatures have been investigated extensively. [1,2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] These investigations can be broadly classified into two groups: (a) studies devoted to the evaluation of tensile properties of different alloys containing a variety of microstructures under potential service conditions, i.e., at temperatures below 1000 ЊC and at a fixed strain rate of ϳ10 Ϫ4 s Ϫ1 ; [4][5][6][7][8][9][10][11] and (b) studies dealing with superplasticity and related phenomena in wrought alloys containing fine, equiaxed aggregates of ␥, ␣ 2 , and ␤ 2 phases. [12][13][14][15][16][17][18] Accordingly, the latter group of studies includes tension tests conducted at temperatures ranging from 900 ЊC to 1250 ЊC and strain rates varying from 10 Ϫ5 to 10 Ϫ2 s Ϫ1 .…”

Section: Introductionmentioning

confidence: 99%

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Plastic-flow and microstructure evolution during hot deformation of a gamma titanium aluminide alloy

Seetharaman,

Semiatin

1997

Metall Mater Trans A

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The hot workability of a near gamma titanium aluminide alloy, Ti-49.5Al-2.5Nb-1.1Mn, was assessed in both the cast and the wrought conditions through a series of tension tests conducted over a wide range of strain rates (10 Ϫ4 to 10 0 s Ϫ1 ) and temperatures (850 ЊC to 1377 ЊC). Tensile flow curves for both materials exhibited sharp peaks at low strain levels followed by pronounced necking and flow localization at high strain levels. A phenomenological analysis of the strain rate and temperature dependence of the peak stress data yielded an average value of the strain rate sensitivity equal to 0.21 and an apparent activation energy of ϳ411 kJ/mol. At low strain rates, the tensile ductility displayed a maximum at ϳ1050 ЊC to 1150 ЊC, whereas at high strain rates, a sharp transition from a brittle behavior at low temperatures to a ductile behavior at high temperatures was noticed. Dynamic recrystallization of the gamma phase was the major softening mechanism controlling the growth and coalescence of cavities and wedge cracks in specimens deformed at strain rates of 10 Ϫ4 to 10 Ϫ2 s Ϫ1 and temperatures varying from 950 ЊC to 1250 ЊC. The dynamically recrystallized grain size followed a power-law relationship with the Zener-Hollomon parameter. Deformation at temperatures higher than 1270 ЊC led to the formation of randomly oriented alpha laths within the gamma grains at low strain levels followed by their reorientation and evolution into fibrous structures containing ␥ ϩ ␣ phases, resulting in excellent ductility even at high strain rates.

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Section: A Plastic Flow Phenomenologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plastic-flow and microstructure evolution during hot deformation of a gamma titanium aluminide alloy

Seetharaman,

Semiatin

1997

Metall Mater Trans A

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“…As a result, a fine grained near g microstructure has been developed in materials with aluminium contents between 46 and 50 at.% after 0966 processing by rolling, extrusion, or forging within the aCg phase field and also following the powder metallurgy route [12]. Creep investigations in fine-grained TiAl materials have been conducted at temperatures above 850 8C [13][14][15][16][17][18][19][20][21][22]. Details of material composition and mechanical parameters are listed in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Superplastic behaviour of two extruded gamma TiAl(Mo,Si) materials

et al. 2005

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“…Button-like ingots with 150 mm in diameter and 13 mm in thickness were obtained. The specimens with a size of 10ϫ10ϫ50 mm 3 were cut by an electric discharging machine. These specimens were wrapped with tantalum foils and encapsulated into quartz tubes filled with high purity argon (99.999%).…”

Section: Methodsmentioning

confidence: 99%

Microstructural Control for Superplasticity Simply by Heat Treatment without Thermomechanical Processing in a Ti-46Al-3.5Cr Alloy.

2000

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Microstructural evolution only by heat treatment has been studied for a Ti-46at%Al-3.5at%Cr alloy, in order to obtain a microstructure which causes superplasticity at high temperatures. By changing the cooling rate from 1 613 K in the a-Ti single-phase region, three kinds of microstructures were identified. Namely, lamellar microstructure appeared by furnace cooling, feathery microstructure took place by air-cooling and massive microstructure prevailed by oil quenching. During subsequent annealing at 1 473 K in the bϩg twophase region, the feathery microstructure turns to fine microdual structure with the equiaxed g grains with 13 mm in grain size and the b precipitates formed along the g grain boundaries. In a tensile test at 1 473 K with a strain rate of 3.2ϫ10 Ϫ4 s Ϫ1, this b/g microdual structure exhibits remarkable superplastic deformation with an elongation of 450 %, which is the same with that obtained by the b/g microdual structure prepared by a thermomechanical processing. On the other hand, the lamellar microstructure and the massive microstructure are not transformed to the b/g microdual structure with the equiaxed g grains, resulting in low elongations of 30 % and 110 % at 1 473 K, respectively. KEY WORDS: titanium aluminide; heat treatment; phase transformation; feathery microstructure; microdual structure; high temperature deformation.1 613 K in the a single-phase region, followed by furnace cooling, air-cooling or oil quenching to obtain the lamellar microstructure, the feathery microstructure or the massive microstructure, respectively. Corresponding to the different cooling methods, the three kinds of specimens are termed as FC, AC and OQ, respectively. After mechanical polishing to remove oxidized surface, the specimens were subsequently annealed at 1 473 K in the bϩg two-phase region for 3.6 ks. The annealed specimens of FC, AC, OQ are called FCA, ACA and OQA, respectively. The tensile specimens with a gauge length of 10 mm and a cross section of 3.5ϫ3.5 mm 2 were prepared from the specimens after annealing. Tensile tests were conducted at 1 473 K with a strain rate of 3.2ϫ10 Ϫ4 s Ϫ1. Microstructural characteristics of as-cooled, annealed and deformed specimens were examined with an optical microscope using polarization and Normarski interference contrast and a scanning electron microscope (SEM). Figure 2 shows optical microstructures of the specimens after solution treatment at 1 613 K for 1.8 ks followed by continuous cooling at various rates. These images in Figs. 2(a)-2(c) and Figs. 2(e)-2(f) were taken from the same area using polarization and Normarski interference contrast microscopy, respectively. As seen in Fig. 2(a) and Fig. 2(d), the sample FC exhibits the lamellar microstructure, which developed with a single orientation in one parent a grain. The lamellar grains corresponding to the parent a grains are extremely large more than one millimeter in size and their grain boundaries exhibit serration. Their thin plates are composed of the a 2 -Ti 3 Al and the g phases. Results and Discu...

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High Temperature Deformation Behavior of Titanium-Aluminide Based Gamma Plus Beta Microduplex Alloy.

Abstract: MasaoA new type of microstructure has been developed by an optimum combination of macroalloying and thermomechanical processing in a high-purity gamma titanium-aluminide based ternary alloy:Ti-47at'/•Al-3at"/.Cr.

Cited by 75 publications

References 2 publications

Plastic-flow and microstructure evolution during hot deformation of a gamma titanium aluminide alloy

Plastic-flow and microstructure evolution during hot deformation of a gamma titanium aluminide alloy

Superplastic behaviour of two extruded gamma TiAl(Mo,Si) materials

Microstructural Control for Superplasticity Simply by Heat Treatment without Thermomechanical Processing in a Ti-46Al-3.5Cr Alloy.

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