scholarly journals IMPACT OF LONG-TERM AGEING ON SIGMA PHASE PRECIPITATION PROCESS IN STEELS WITH AUSTENITIC MATRIX

2021 ◽  
Vol 72 (4) ◽  
pp. 31-39
Author(s):  
Adam Zieliński
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Operating Temperature ◽  
Ageing Time ◽  
Precipitation Process ◽  
Austenitic Matrix ◽  
Phase Precipitation ◽  
Transmission Electron ◽  
Microstructure Examination

Super 304H, HR3C and Sanicro 25 grade austenitic matrix steels are used in the construction of pressure components of boilers with supercritical operating parameters. The article presents the results of microstructure examination in delivery condition and after age-ing for up to 50,000 hours at 700°C. The microstructure exami-nation was performed using scanning and transmission electron microscopy. The precipitates were identified using transmission electron microscopy. In particular, the study analysed the v phase precipitation process and its dynamics depending on the ageing time. It has been shown that the intermetallic v phase plays a significant role in the loss of durability of the tested steel. It is related to its significant increase due to the influence of high temperature, and its coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quan-titative identification of the intermetallic v phase precipitation pro-cess described in the study is important in the analysis of the loss of durability of the tested steels under creep conditions.

Crystallographic characteristics of the process of σ-phase precipitation in chromium–nickel austenitic steels

1983 ◽  
Vol 16 (6) ◽  
pp. 590-598 ◽  
Author(s):  
J. Barcik
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Austenitic Steels ◽  
Precipitation Process ◽  
Phase Precipitation ◽  
Transition Matrices ◽  
Σ Phase ◽  
Transmission Electron ◽  
Crystallographic Characteristics ◽  
Austenite Grains

Transmission electron microscopy has been used to determine the crystallographic characteristics of the σ-phase precipitation process in austenitic steels. The σ-phase precipitating inside the austenite grains was found to exhibit a close similarity to the austenite described by Nenno, Tagaya & Nishijama [Trans. Jpn. Inst. Met. (1962), 3, 82–91]. Transition matrices of the austenite planes and direction indices to the a phase have been determined. The σ-phase lamellae were found to lie on the {111} austenite plane which is their habit plane and grow most rapidly in the 〈112〉 γ direction. The habit of these lamellae are bound by four {110}σ and two {001}σ σ-phase planes.

scholarly journals In VitroEffects of Novel Ruthenium Complexes in Neospora caninum and Toxoplasma gondii Tachyzoites

2013 ◽  
Vol 57 (11) ◽  
pp. 5747-5754 ◽  
Author(s):  
Fabienne Barna ◽  
Karim Debache ◽  
Carsten A. Vock ◽  
Tatiana Küster ◽  
Andrew Hemphill
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Toxoplasma Gondii ◽  
Neospora Caninum ◽  
Ruthenium Complexes ◽  
Term Treatment ◽  
Content Type ◽  
Transmission Electron ◽  
Long Term Treatment

ABSTRACTUpon the screening of 16 antiproliferative compounds againstToxoplasma gondiiandNeospora caninum, two hydrolytically stable ruthenium complexes (compounds 16 and 18) exhibited 50% inhibitory concentrations of 18.7 and 41.1 nM (T. gondii) and 6.7 and 11.3 nM (N. caninum). To achieve parasiticidal activity with compound 16, long-term treatment (22 to 27 days at 80 to 160 nM) was required. Transmission electron microscopy demonstrated the rapid impact on and ultrastructural alterations in both parasites. These preliminary findings suggest that the potential of ruthenium-based compounds should thus be further exploited.

The Effect of Composition and Temperature on the Ageing Response of some Dilute 6xxx Series Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 227-232 ◽  
Author(s):  
C.N. Aiza Jaafar ◽  
Gordon W. Lorimer ◽  
N.C. Parson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Solution Treatment ◽  
Precipitation Process ◽  
Microstructural Development ◽  
Solution Treatment Temperature ◽  
Artificial Ageing ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
6Xxx Series

The effects of composition and temperature on the ageing response and the microstructural development during ageing treatment of a series of dilute 6xxx series alloys have been investigated. The alloys contained between 0.22 and 0.79 wt% Si and 0.20 and 0.51 wt% Mg. Some of the alloys were copper-free, 0.001-0.002 wt% Cu, while others contained additions of 0.1 wt% Cu. Some of the alloys were ‘balanced’ while others contained excess Si (ExSi). The effects of solution treatment temperature and artificial ageing (T6) on the precipitation process were investigated using various techniques, including differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and analytical transmission electron microscopy (ATEM). MT DATA has been used to predict the phase relationships as a function of temperature and the MT DATA predictions have been compared with the phases observed by DSC and ATEM. The morphology and crystal structures of the precipitates formed were monitored by TEM. The results showed a correlation between the composition and the ageing response of the alloys.

Effect of Process Parameters on Microstructures of 7055 Aluminum Alloy in Creep Age Forming

2011 ◽  
Vol 80-81 ◽  
pp. 40-45 ◽  
Author(s):  
Li Hua Zhan ◽  
Yan Guang Li ◽  
Ming Hui Huang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Aluminum Alloy ◽  
Grain Boundary ◽  
Process Parameters ◽  
Ageing Time ◽  
Aged Alloy ◽  
Transmission Electron ◽  
7055 Aluminum Alloy ◽  
Creep Age Forming

The effects of process parameters on evolution of microstructures of 7055 aluminum alloy in creep age forming were studied and the microstrucures were analyzed using transmission electron microscopy (TEM). Some important results are obtained: with the increasing of ageing time, the size of platelet shaped (known as Guinier-Preston (G-P) zones) precipitates and spherical shaped η' precipitates increased, the number of platelet shaped precipitates increased too, while the number of η' precipitates decreased; the precipitates with almost the same size distributed continuously and uniformly along the grain boundary with quite narrow precipitate free zones (PFZs) at 5 hours of ageing time, when the ageing time increases to 8 hours, the distribution of the precipitates along the grain boundary becomes discontinuous and the PFZs gets wider, while with the further increasing of the ageing time, the precipitates distributed continuously again along the grain boundary and the PFZs become more wider. From comparison of stress-aged alloy to stress-free-aged alloy, it was found that after 20 hours ageing, the precipitates in the stress-aged alloy are slightly coarser and the PFZs are wider, the density of retained η' is lower with the development of η phase.

scholarly journals Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

2016 ◽  
Vol 61 (2) ◽  
pp. 957-964 ◽  
Author(s):  
A. Zieliński ◽  
J. Dobrzański ◽  
H. Purzyńska ◽  
G. Golański
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Phase Composition ◽  
High Chromium ◽  
X Ray ◽  
Supercritical Steam Parameters ◽  
Transmission Electron ◽  
Steam Parameters

AbstractThis paper presents the characteristics of the performance of P91 (X10CrMoVNb9-1), P92 (X10CrWMoVNb9-2) and VM12 (X12CrCoWVNb12-2-2) steels used for condition assessment of the pressure components of boilers with supercritical steam parameters. Studies on the mechanical properties, microstructure tests using scanning and transmission electron microscopy, and X-ray analysis of the phase composition of precipitates were performed for selected steels in the as-received condition and after long-term annealing. These steel characteristics are used for the evaluation of the microstructural changes and mechanical properties of the material of components after long-term service. The result of this study is the database of material characteristics representing the mechanical properties related to the microstructure analysis and it can be used for diagnosis of the components of pressure parts of power boilers.

scholarly journals Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2

2008 ◽  
Vol 64 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Tom Baikie ◽  
Cristiano Ferraris ◽  
Wim T. Klooster ◽  
S. Madhavi ◽  
Stevin S. Pramana ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Photoelectron Spectroscopy ◽  
Arsenic Speciation ◽  
X Ray ◽  
Transmission Electron ◽  
Landfill Disposal

The crystal chemistries of synthetic mimetite, Pb10(As5+O4)6(Cl2 − x O x/2), a neutral apatite, and finnemanite, Pb10(As3+O3)6Cl2, a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P63/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites. A better understanding of the mixed arsenic speciation in apatites can guide the formulation of waste form ceramics and improve models of long-term durability after landfill disposal.

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