High-Temperature Phase Transformation in Cr Added TiAl Base Alloy

1998 ◽  
Vol 552 ◽  
Author(s):  
E. Abe ◽  
K. Niinobe ◽  
M. Nobuki ◽  
M. Nakamura ◽  
T. Tsujimoto
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Base Alloy ◽  
Small Degree ◽  
Phase Region ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Air Cooling ◽  
Two Phase ◽  
Transmission Electron

ABSTRACTWe have investigated a microstructure evolution of a Ti-48Al-3.5Cr (in at.%) alloy at high-temperatures (>1473K). In the alloy annealed at 1673K for 1.8ks, followed by air-cooling, a characteristic microstructure with a feathery fashion was uniformly formed. From a cooling-rate-controlling study, it was found that formation of the feathery structure is accomplished during continuous cooling from 1673K to 1573K, within the α+γ two-phase region. Transmission electron microscopy revealed that the feathery structure is composed of lamellar colonies (5–10µm) which are crystallographicaly tilted slightly (a few degree) with their neighbors. A surprising fact is that lamellae in each colony are mostly the γphase with few α2 phase less than 5% in volume. This suggests that the feathery structure is a metastable product and has not resulted from the α → α+γ transformation above 1573K. Instead, the feathery structure formation should be attributed to the non-equilibrium α → γtransformation which occurs at high-temperatures with a small degree of supercooling. We discuss this interesting phase transformation in terms of the α→γ massive transformation, based on the continuous-coolingtransformation (CCT) diagram constructed for the present alloy.

scholarly journals Aging Behavior and Precipitation Analysis of Cu-Ni-Co-Si Alloy

Crystals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 435
Author(s):  
Xiangpeng Xiao ◽  
Jian Huang ◽  
Jinshui Chen ◽  
Hai Xu ◽  
Zhao Li ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Aging Process ◽  
Kinetic Curve ◽  
Kinetic Equations ◽  
Phase Region ◽  
Transformation Kinetic ◽  
Precipitation Kinetic ◽  
Two Phase ◽  
Transmission Electron ◽  
Co Addition

Cu-Ni-Si alloy with a different Co content was prepared by inductive melting and hot rolling. The alloy was solution treated at 950 °C for 1.5 h and aged at 450 °C, 500 °C, and 550 °C for different times. The phase diagram calculation and transmission electron microscopy was used to investigate the effect of Co addition on the aging precipitation behavior of the Cu-Ni-Si alloy. The phase transformation kinetics equation was calculated as well. The results show that, with the increase of aging temperature, the two-phase region of Fcc + Ni2Si in the Cu-Ni-Si ternary diagram would get wider. Some NixSiy phases would also form in the Cu-rich isothermal section. The addition of Co would replace part of Ni to form the (Ni, Co)2Si phase, which inhibits the spinodal decomposition process of the Cu-Ni-Si alloy during the aging process. The precipitated phase of the Cu-Ni-Si alloy with a high content of the Co element is more likely to grow with the extension of aging time. The phase transformation kinetic equations of the Cu-Ni-Si alloy at 450 °C and 500 °C showed good agreement with the experimental results. Furthermore, it can be seen from the precipitation kinetic curve the addition of the Co element accelerates precipitation in the aging process.

scholarly journals Revisiting the Bøggild Intergrowth in Iridescent Labradorite Feldspars: Ordering, Kinetics, and Phase Equilibria

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 727
Author(s):  
Shiyun Jin ◽  
Huifang Xu ◽  
Seungyeol Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atom Probe ◽  
Phase Region ◽  
Two Phase ◽  
Subsolidus Phase ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

The enigmatic Bøggild intergrowth in iridescent labradorite crystals was revisited in light of recent work on the incommensurately modulated structures in the intermediated plagioclase. Five igneous samples and one metamorphic labradorite sample with various compositions and lamellar thicknesses were studied in this paper. The lamellar textures were characterized with conventional transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The compositions of individual lamellae were analyzed with high-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and atom probe tomography (APT). The average structure states of the studied samples were also compared with single-crystal X-ray diffraction data (SC-XRD). The Na-rich lamellae have a composition of An44–48, and the Ca-rich lamellae range from An56 to An63. Significant differences between the lamellar compositions of different samples were observed. The compositions of the Bøggild intergrowth do not only depend on the bulk compositions, but also on the thermal history of the host rock. The implications on the subsolidus phase relationships of the plagioclase feldspar solid solution are discussed. The results cannot be explained by a regular symmetrical solvus such as the Bøggild gap, but they support an inclined two-phase region that closes at low temperature.

scholarly journals Effect of Reverse-phase Transformation Annealing Process on Microstructure and Mechanical Properties of Medium Manganese Steel

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1633 ◽  
Author(s):  
Yan Zhao ◽  
Lifeng Fan ◽  
Bin Lu
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Phase Region ◽  
Manganese Steel ◽  
Reverse Phase ◽  
Two Phase ◽  
Fine Grain ◽  
Martensite Microstructure

In order to develop a third-generation automobile steel with powerful strength and elongation, we propose a method through high temperature quenching and two-phase region reverse-phase transformation annealing to develop such steel with 0.13% C and 5.4% Mn. To investigate the microstructure evolution and mechanical properties of manganese steel, SEM, XRD and TEM are employed in our experiments. Experimental results indicate that the microstructure after quenching is mainly lath martensite microstructure with average of lath width at 0.5 μm. The components of the steel after along with reverse-phase transformation annealing are ultra-fine grain ferrite, lath martensite and different forms of austenite microstructure. When the temperature at 625 °C, the components of the steel mainly includes lath martensite microstructure and ultra-fine grain ferrite and the fraction of austenite volume is only 5.09%. When the annealing temperature of reverse-phase transformation increase into 650 °C and 675 °C, the austenite appears in the boundary of the ferritic grain boundary and the boundary of lath martensite as the forms of bulk and lath. The phenomenon appears in the bulk of austenite, and the size of is 0.22 μm, 0.3 μm. The fraction of austenite volume is 22.34% at 675 °C and decreases into 9.32% at 700 °C. The components of austenite mainly includes ultra-fine grained ferrite and lath martensite. Furthermore, the density of decreases significantly, and the width of martensite increases into 0.32 μm. In such experimental settings, quenching at 930 °C with 20 min and at 675 °C with 30 min reverse-phase transformation annealing, the austenite volume fraction raises up to 22.34%.

Humidity sensitive irreversible phase transformation of an open-framework Zinc phosphate and its water-assisted high proton conduction properties

2021 ◽  
Author(s):  
Jing-Wei Yu ◽  
Hai-Jiao Yu ◽  
Qiu Ren ◽  
Jin Zhang ◽  
Yang Zou ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Zinc Phosphate ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Open Framework ◽  
High Proton ◽  
Irreversible Phase Transformation ◽  
Low Temperature Phase ◽  
Conduction Properties

Open-framework zinc phosphate (NMe4)(ZnP2O8H3) undergoes irreversible phase transformation. Structural transformation with α (NMe4.Zn[HPO4][H2PO4] the low-temperature phase) and β (NMe4.ZnH3[PO4]2 the high-temperature phase) (Tc=149 °C) and conduction properties were investigated by...

Experimental Investigations of the High-Temperature Phase Relationship and Ordering Transition in Ni-Mn-Ga Ternary System

2010 ◽  
Vol 148-149 ◽  
pp. 1695-1700
Author(s):  
Yun Qing Ma ◽  
Shui Yuan Yang ◽  
Ryosuke Kainuma ◽  
Kiyohito Ishida ◽  
Cui Ping Wang ◽  
...  
Keyword(s):  
Ternary System ◽  
Phase Relationship ◽  
Phase Region ◽  
High Temperature Phase ◽  
Experimental Investigations ◽  
Temperature Phase ◽  
Critical Temperatures ◽  
Disorder Transition ◽  
Mn Content ◽  
Ordering Transition

The phase equilibria at 900 °C and B2/L21 order-disorder transition in the Ni-Mn-Ga ternary system were investigated by analyzing the equilibrated alloys and diffusion couples using a combination of techniques. It was confirmed that a bcc single phase region exists in a wide composition range at 900 °C, and the critical temperatures of B2/L21 order-disorder transition were determined in Ni-50 at.% section, which exhibits a maximal ordering transition temperature of 796 at Mn content of 25 at.%. The obtained results will be helpful for the preparation and annealing of Ni-Mn-Ga alloys in the specific temperature.

Investigation of Ni Doped Ge-Te Materials for High Temperature Phase Change Memory Applications

2016 ◽  
Vol 848 ◽  
pp. 460-465
Author(s):  
Liang Liang Cao ◽  
Liang Cai Wu ◽  
Zhi Tang Song ◽  
Wen Qing Zhu ◽  
Yong Hui Zheng ◽  
...  
Keyword(s):  
High Temperature ◽  
Phase Change ◽  
High Speed ◽  
Random Access ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Change Behavior ◽  
Transmission Electron ◽  
Ni Addition ◽  
Memory Applications

Ni-doped Ge-Te (Ni-GT) material was proposed and investigated for phase change random access memory (PCRAM) applications. With Ni addition, the crystallization temperature, data retention ability and crystallization speed were obviously improved. The surface roughness of crystalline Ni-GT films was decreased by Ni incorporation. Moreover, temperature dependent transmission electron microscopy (TEM) was applied to investigate the phase change behavior of Ni-GT films. All the experimental results demonstrated that Ni-GT material has potential for high-speed PCRAM applications in high temperature environment.

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