scholarly journals Phase Transformations and Recrystallization Processes During Synthesis, Processing and Service of TiAl Alloys

10.5772/34972 ◽  
2012 ◽  
Author(s):  
Fritz Appel
Keyword(s):  
Phase Transformations ◽  
Tial Alloys

Microsegregation, macrosegregation and related phase transformations in TiAl alloys

2011 ◽  
Vol 19 (6) ◽  
pp. 749-756 ◽  
Author(s):  
D. Daloz ◽  
U. Hecht ◽  
J. Zollinger ◽  
H. Combeau ◽  
A. Hazotte ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Tial Alloys ◽  
Related Phase

Phase Transformations and Grain Growth in β-stabilized TiAl Alloys

2014 ◽  
Vol 159 (7) ◽  
pp. 289-290
Author(s):  
Thomas Klein ◽  
Salar Niknafs ◽  
Rian Dippenaar ◽  
Helmut Clemens ◽  
Svea Mayer
Keyword(s):  
Phase Transformations ◽  
Grain Growth ◽  
Tial Alloys

On Phase Equilibria and Phase Transformations in β/γ-TiAl Alloys – A Short Review

2011 ◽  
Vol 156 (11) ◽  
pp. 438-442 ◽  
Author(s):  
Svea Mayer ◽  
Christian Sailer ◽  
Thomas Schmoelzer ◽  
Helmut Clemens ◽  
Thomas Lippmann ◽  
...  
Keyword(s):  
Phase Equilibria ◽  
Phase Transformations ◽  
Short Review ◽  
Tial Alloys

First-principles study of deformation-induced phase transformations in Ti–Al intermetallics

2009 ◽  
Vol 24 (5) ◽  
pp. 1662-1666 ◽  
Author(s):  
C.L. Chen ◽  
W. Lu ◽  
L.L. He ◽  
H.Q. Ye
Keyword(s):  
Phase Transformations ◽  
Intermetallic Compounds ◽  
Density Functional ◽  
Structural Phase ◽  
Generalized Gradient ◽  
Theoretical Understanding ◽  
Functional Theory ◽  
Tial Alloys ◽  
The Stability ◽  
Formation Energies

The structural phase stability and electronic properties of the Ti–Al intermetallic compounds were investigated by means of density-functional theory (DFT) calculations in a generalized gradient approximation. Through comparison of the calculated formation energies of the parent and product phases, an in-depth theoretical understanding of the deformation-induced γ ↔ α2 phase transitions observed previously in TiAl alloys was achieved. The formation energy plays an important role in evaluating the feasibility of these phase transformations during plastic deformation of TiAl alloys. In addition, the density of states (DOS) was also calculated and used to analyze the stability of Ti–Al intermetallic compounds. The reasons for the absence of the deformation-induced (DI)-α2 and DI-γ (L12) phases in underformed TiAl alloys were analyzed.

Ordered α2 to ωo phase transformations in high Nb-containing TiAl alloys

2015 ◽  
Vol 91 ◽  
pp. 330-339 ◽  
Author(s):  
Lin Song ◽  
Xiangjun Xu ◽  
Li You ◽  
Yongfeng Liang ◽  
Yanli Wang ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Tial Alloys

Structure of second phases in TiAl alloys containing Cr and B

1991 ◽  
Vol 49 ◽  
pp. 576-577
Author(s):  
Ernest L. Hall ◽  
Shyh-Chin Huang
Keyword(s):  
Grain Size ◽  
Second Phase ◽  
Structure And Properties ◽  
Tial Alloys ◽  
Second Phases ◽  
Interstitial Elements

Addition of interstitial elements to γ-TiAl alloys is currently being explored as a method for improving the properties of these alloys. Previous work in which a number of interstitial elements were studied showed that boron was particularly effective in refining the grain size in castings, and led to enhanced strength while maintaining reasonable ductility. Other investigators have shown that B in γ-TiAl alloys tends to promote the formation of TiB2 as a second phase. In this study, the microstructure of Bcontaining TiAl alloys was examined in detail in order to describe the mechanism by which B alters the structure and properties of these alloys.

The use of high-resolution FESEM to study solid-state phase transformations and reactions

1994 ◽  
Vol 52 ◽  
pp. 1028-1029
Author(s):  
P. G. Kotula ◽  
D. D. Erickson ◽  
C. B. Carter
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
High Efficiency ◽  
Sol Gel ◽  
Quantitative Information ◽  
Solid State Reactions ◽  
Critical Dimensions ◽  
Backscattered Electrons ◽  
Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

1993 ◽  
Vol 51 ◽  
pp. 842-843
Author(s):  
K. Barmak
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Transformations ◽  
Analytical Electron Microscopy ◽  
Ex Situ ◽  
Multilayer Thin Films ◽  
Absolute Concentration ◽  
Analytical Electron ◽  
Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

A Transmission Electron Microscopical Investigation of Phase Transformations in TiNi

1980 ◽  
Vol 38 ◽  
pp. 340-341
Author(s):  
P. Moine ◽  
G. M. Michal ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Applied Stress ◽  
Structural Changes ◽  
Microscopical Investigation ◽  
Temperature Range ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Diffraction Effects ◽  
Microscopy Images

Premartensitic effects in near equiatomic TiNi have been pointed out by several authors(1-5). These include anomalous contrast in electron microscopy images (mottling, striations, etc. ),diffraction effects(diffuse streaks, extra reflections, etc.), a resistivity peak above Ms (temperature at which a perceptible amount of martensite is formed without applied stress). However the structural changes occuring in this temperature range are not well understood. The purpose of this study is to clarify these phenomena.

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