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.

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 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%.

Microstructure and Properties of Cu-Cr-Zr-Ag Alloy

2018 ◽  
Vol 941 ◽  
pp. 1613-1617 ◽  
Author(s):  
Li Jun Peng ◽  
Xu Jun Mi ◽  
Hao Feng Xie ◽  
Yang Yu ◽  
Guo Jie Huang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Phase Transformation ◽  
High Resolution ◽  
Aging Process ◽  
Precipitation Sequence ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
The Matrix

The Cr precipitation sequence in Cu-Cr-Zr-Ag alloy during the aging process at 450°C could be obtained by Transmission electron microscopy (TEM) and High-resolution transmission microscopy (HRTEM) in the study. The strengthening curve shows a unimodal type and the tensile strength trends to peak when the aged for 4h. The Cr phase transformation of Cu-Cr-Zr-Ag aged at 450°C is supersaturated solid sloution→G.P zones→fcc Cr phase→order fcc Cr phase→bcc Cr phase. The orientation relationship between bcc Cr precipitates and the matrix change from cube-on-cube to NW-OR.

Effect of Two-Phase Region Quenching Temperature on Microstructure Evolution and Microhardness of HSLA100 Steel

2012 ◽  
Vol 602-604 ◽  
pp. 380-384
Author(s):  
X. Yan ◽  
G.F. Zhou ◽  
C.M. Zhu ◽  
J.S. Guan
Keyword(s):  
Microstructure Evolution ◽  
Volume Fraction ◽  
High Strength ◽  
Phase Region ◽  
Two Phase ◽  
Quenching Temperature ◽  
Island Structure ◽  
Transmission Electron ◽  
Evolution Characteristics ◽  
Lath Bainite

The microstructure evolution characteristics and those effects on microhardness of HSLA (high strength low alloy) 100 steel secondary quenched in the two-phase region were investigated. The results show that the mixed microstructure of ferrite and the M-A（mastenite-austenite）islands can be obtained in the intercritical quenching region. A small amount of island structure distributing along the lath ferrite quenched at 700°C is observed by transmission electron microscope (TEM). With the quenching temperature increasing, the island structure increases in quantity and coarsens in shape, at the same time, the ferrite gradually transform from single lath morphology to polygonal shape with the dislocation density lowing. When quenched at 820°C, the microstructure reverts to lath bainite. There is a good correlation between Vickers hardness value and the volume fraction of martensite or bainite HSLA100 steel quenched in the two-phase region. The microhardness value of the steel continually increase from 240HV to 320HV quenched at the range of 700°C to 820°C, and then keep a very small fluctuation around 320HV when the temperature exceeds to 820°C.

Phase-Separations of Coherent Precipitates of Ordered Phases in Elastically Constrained Alloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Minoru Doi ◽  
Hiroshi Kumagai ◽  
Kanako Nakashima ◽  
Takao Kozakai
Keyword(s):  
Phase Separation ◽  
Phase Region ◽  
Point Of View ◽  
Two Phase ◽  
Phase Separations ◽  
Transmission Electron ◽  
Ordered Phases ◽  
Chemical Free Energy ◽  
Fe Alloys ◽  
Means Of Transmission

AbstractPhase-separations of coherent precipitates of ordered phases were investigated by means of transmission electron microscopy (TEM) and the theoretical analysis from a thermodynamic point of view. When the two-phase microstructures of A1+L12 in elastically constrained Ni-Al-Ti and Ni-Si-Fe alloys are isothermally heated inside the two-phase region of A1+L12 , coherent L12 precipitate particles sometimes exhibit a phase-separation and A1 phase newly appears and grows in L12 particles. Phase-separations of the same type as the above are also observed in coherent two-phase microstructures of A2+D03 and A2+B2 in elastically constrained Fe-Si-V and Fe-Al-Ni alloys respectively: coherent D03 or B2 precipitates exhibit a phase-separation and A2 phase newly appears and grows in both precipitates. Such phase-separation is realized under the influence of chemical free energy and elastic energies.

scholarly journals Deformation and Phase Transformation of Disorder α Phase at (α+γ) two Phase Region in high Nb Containing TiAl alloy

2021 ◽  
Author(s):  
Haitao Zhou ◽  
Fantao Kong ◽  
Yanbo Wang ◽  
Xiangwu Hou ◽  
Ning Cui ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Tial Alloy ◽  
Temperature Drop ◽  
Alpha Phase ◽  
Phase Region ◽  
Two Phase ◽  
Α Phase ◽  
Assisted Decomposition

In this paper, the deformation and phase transformation of disorder α phase at (α + γ) two phase region in as-forged Ti-44Al-8Nb-(W, B, Y) alloy are investigated by hot compression and hot packed rolling. Detailed microstructural evolution demonstrates that the as-deformed microstructure is significantly affected by deformation conditions. The mircrostructure differences are mainly due to temperature drop and strain rate. The evolution of α lamelae into α grains is detailed descripted. Moreover, the disorder α lamellae can also be decomposed into some new α grains by the assisted decomposition mechanism of γ grains. Microstructure evolution model of current TiAl alloy at 1250 °C during hot rolling is built.

The Prediction of the Flow Stress of an Extra-Low Carbon Steel in the Two-Phase Region Using Continuous Cooling Curves

1996 ◽  
Vol 118 (4) ◽  
pp. 463-470 ◽  
Author(s):  
Yhu-Jen Hwu ◽  
J. G. Lenard ◽  
J. J. M. Too
Keyword(s):  
Phase Transformation ◽  
Flow Stress ◽  
Carbon Steel ◽  
Volume Fraction ◽  
Low Carbon Steel ◽  
Phase Region ◽  
Cooling Curves ◽  
Low Carbon ◽  
Two Phase ◽  
Continuous Cooling

Continuous cooling curves of an extra-low carbon steel under three cooling rates are measured. The flow stress of the steel is established in compression tests during which the temperature is continuously decreasing. The phase transformation temperatures are determined from the cooling rate curve. The latent heat during phase transformation is calculated. A new variable, related to the volume fraction of transformation, is defined. Experimental results show that the relationship between the softening ratio of the flow stress due to phase transformation and this new variable may be described by a quadratic relationship. Based on this relationship and the continuous cooling curves, the flow stresses in the two-phase region are successfully predicted.

Alloy Effects And Extended Solubilities In Binary Mixtures Of Nanometer-Sized Fe-Cu Crystals

1991 ◽  
Vol 238 ◽  
Author(s):  
J. Eckert ◽  
R. Birringer ◽  
J. C. Holzer ◽  
C. E. Krill ◽  
W. L. Johnson
Keyword(s):  
Binary Mixtures ◽  
Phase Region ◽  
Alloy Formation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Transmission Electron ◽  
Thermodynamic Conditions ◽  
20 Nm

ABSTRACTBinary mixtures of Fe-Cu powders in the range of 10–95 at.% Fe have been prepared by mechanical alloying and investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The final grain sizes of the powders vary between 6 and 20 nm, and depend on the composition of the material. Indications for the formation of single-phase alloys with up to 60 at.% Fe in Cu and 20 at.% Cu in Fe have been found although the Fe-Cu system exhibits only vanishingly small solid solubilities under equilibrium conditions. Between 60 at.% and 80 at.% Fe a two-phase region of fee and bec solid solutions exists. Alloy formation is discussed with respect to the thermodynamic conditions of the material. The influence of the large grain boundary fraction, as well as the role of internal strains and stored enthalpies introduced by ball milling, is critically assessed.

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