Effect of Nb, Zr and Zr+Hf on the lattice parameters of the intermetallic phases and creep behavior of γ-TiAl alloys based on Ti-44Al-0.2B

Fine-grained fully lamellar (FGFL) structures of XD TiAl alloys (Ti-45 and 47Al-2Nb-2Mn+0.8vol.%TiB2) (at.%) were stabilized to varying degrees by different aging treatments. Specimens with and without aging were creep tested at 760°C and 207 MPa. It was found that during creep deformation, degradation of the lamellar structure involving coarsening within the colonies and spheroidization at colony boundaries occurred, forming fine globular structures at the colony boundaries and increasing the creep rate. Aging treatments stabilized the lamellar structure and retarded the coarsening and spheroidization processes during creep deformation. As a result, the aged specimens exhibited lower minimum creep rates and longer creep lives than the unaged specimens. A multiple step aging stabilized the lamellar structure to the greatest extent and suppressed other degradation processes during aging, resulting in the best creep resistance. These results demonstrate that the multiple step aging is the optimal aging condition for stabilizing FGFL XD TiAl alloys.

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Texture Formation during Hot-Deformation of High-Nb Containing γ-TiAl Based Alloys

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.160.301 ◽

2010 ◽

Vol 160 ◽

pp. 301-306 ◽

Cited By ~ 6

Author(s):

A. Stark ◽

Frank Peter Schimansky ◽

Helmut Clemens

Keyword(s):

Dynamic Recrystallization ◽

Hot Deformation ◽

Elevated Temperatures ◽

Intermetallic Phases ◽

Texture Formation ◽

Microstructure Formation ◽

Tial Alloys ◽

Deformation Textures ◽

Transus Temperature ◽

Similar Texture

In this study texture and microstructure formation in high-Nb containing TiAl alloys during lab-scale compression experiments and “near conventional” forging on an industrial scale are investigated. The deformation temperatures range from 700 °C up to temperatures close to the α transus temperature (Tα = 1295 °C). Depending on the deformation conditions, the texture of the tetragonal γ-TiAl phase is formed by pure deformation components, components related to dynamic recrystallization, or transformation components. This changing corresponds with microstructural observations. The hexagonal phases α2-Ti3Al and α-Ti(Al) show a similar texture as it is known for Ti and Ti-base alloys after compressive deformation at elevated temperatures. In contrast to the γ texture, no significant change of the α/α2 texture was observed in the investigated temperature range. In the alloy with a composition of Ti-45Al-10Nb (in at.%) even deformation textures of ternary intermetallic phases, as the hexagonal ωo-Ti4Al3Nb and the cubic βo-TiAl(Nb) phase, respectively, were measured and analyzed.

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Accurate determination of the lattice parameters of ?-TiAl alloys

Journal of Materials Science Letters ◽

10.1007/bf00274384 ◽

1996 ◽

Vol 15 (14) ◽

pp. 1231-1233 ◽

Cited By ~ 9

Author(s):

E. S. K. Menon ◽

A. G. Fox ◽

R. Mahapatra

Keyword(s):

Accurate Determination ◽

Lattice Parameters ◽

Tial Alloys

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Effect of intermetallic phases on the creep behavior of AZ91 magnesium alloy

Materials Science and Engineering A ◽

10.1016/j.msea.2009.10.008 ◽

2010 ◽

Vol 527 (6) ◽

pp. 1395-1403 ◽

Cited By ~ 75

Author(s):

A. Srinivasan ◽

J. Swaminathan ◽

M.K. Gunjan ◽

U.T.S. Pillai ◽

B.C. Pai

Keyword(s):

Magnesium Alloy ◽

Creep Behavior ◽

Intermetallic Phases ◽

Az91 Magnesium Alloy ◽

Az91 Magnesium

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Effect of microstructural stability on creep behavior of 47XD TiAl alloys with fine-grained fully lamellar structure

Scripta Materialia ◽

10.1016/j.scriptamat.2004.08.027 ◽

2005 ◽

Vol 52 (1) ◽

pp. 45-50 ◽

Cited By ~ 30

Author(s):

Hanliang Zhu ◽

D.Y. Seo ◽

K. Maruyama ◽

P. Au

Keyword(s):

Creep Behavior ◽

Lamellar Structure ◽

Microstructural Stability ◽

Tial Alloys ◽

Fine Grained ◽

Fully Lamellar

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HREM Analysis of TiB2 - Ti3B4 Precipitates Grown in-Situin TiAl

Microscopy and Microanalysis ◽

10.1017/s1431927600010011 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 625-626

Author(s):

B.J. Inkson ◽

M. Rühle

Keyword(s):

High Strength ◽

Intermetallic Phases ◽

Atomic Scale ◽

Growth Mechanisms ◽

Tial Alloys ◽

Alloying Additions ◽

Titanium Borides ◽

Intermetallic Matrix ◽

First Time

TiAl alloys are being developed for future use as lightweight, high strength structural materials for the aerospace and automotive industries. The growth of titanium borides in-situ in a TiAl melt can lead to a variety of structures, such as TiB (Bf and B27 structures) and TiB2, depending on the Ti/Al ratio in the melt, and on the presence of further alloying additions [1,2]. The morphologies of the boride particles can be significantly altered if they grow coupled with other boride or intermetallic phases [2-4]. Since the morphology and distribution of the borides with the intermetallic matrix can significantly affect their effectiveness as creep reinforcements, the structures and growth mechanisms of these composites need to be quantified at the atomic scale.In a Ti-45.5at.%Al-1.6at.%Fe-l.lat.%V-0.7at.%B alloy know to contain TiB2 precipitates [2,3], the morphology of the boride particles have been investigated using HREM. The Stuttgart JEOL-ARM, operated at 1250kV using the side-entry pole-piece with 0.12nm point resolution, enables the distinction between individual boron and titanium columns in the titanium borides to be achieved for the first time.

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Microstructural Characteristics and Creep Behavior of 45XD TiAl Alloys

MATERIALS TRANSACTIONS ◽

10.2320/matertrans.45.2618 ◽

2004 ◽

Vol 45 (8) ◽

pp. 2618-2621 ◽

Cited By ~ 17

Author(s):

Hanliang Zhu ◽

Dongyi Seo ◽

Kouichi Maruyama

Keyword(s):

Creep Behavior ◽

Microstructural Characteristics ◽

Tial Alloys

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Reaction-Assisted Diffusion Bonding of Advanced Materials

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.297-301.972 ◽

2010 ◽

Vol 297-301 ◽

pp. 972-977 ◽

Cited By ~ 13

Author(s):

Ana Sofia Ramos ◽

M. Teresa Vieira ◽

Sonia Simões ◽

Filomena Viana ◽

Manuel F. Vieira

Keyword(s):

Diffusion Bonding ◽

Intermetallic Phase ◽

Multilayer Films ◽

Intermetallic Phases ◽

Advanced Materials ◽

Tial Alloys ◽

Diffusion Layers ◽

Base Materials ◽

State Diffusion ◽

Hardness Increase

The aim of this work is to join -TiAl intermetallics to Ni based superalloys by solid state diffusion bonding. The surface of the -TiAl alloys and Ni superalloys to be joined was prepared by magnetron sputtering with a few microns thick Ni/Al reactive multilayer thin films with nanometric modulation periods. Sound joining without cracks or pores is achieved along the central region of the bond, especially at 800°C and when a 14 nm period Ni/Al film is used as filler material. During the diffusion bonding experiments interdiffusion and reaction inside the Ni/Al multilayer thin film and between the interlayer film and the base materials is promoted with the formation of intermetallic phases. The final reaction product in the multilayer films is the B2-NiAl intermetallic phase. The interfacial diffusion layers between the base materials and the multilayer films should correspond to: 3-NiTiAl and 4-Ni2TiAl phases from the -TiAl side; Ni-rich aluminide and -phase from the Inconel side. These intermetallic phases are responsible for the hardness increase observed on the diffusion layers.

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